Exam 5

littoral

(coastal) zone

stream gaging stations

6000 stations operated by The U.S. Geological Survey, operate on solar energy, measure stream discharge in an automated fashion, and send their data to a satellite that relays them to a receiving station

ice age

A period during which significant areas of the middle latitudes are covered by glaciers, Today glaciers cover about 10% of Earth's land surface at high latitudes and high elevations on all continents except Australia

interglacial

Between each period of maximum ice advance, during which the enormous continental ice sheets, ice caps, and sea ice retreated and almost completely disappeared

ice caps

Ice masses similar to ice sheets but smaller than 50,000 square kilometers, are present on Iceland and some Arctic islands

diurnal tidal regime

In a few seas that have restricted access to the open ocean, such as the Gulf of Mexico, tidal patterns of only one high and one low tide occur during a tidal day, not very common

arêtes

Jagged, narrow ridges of rock between cirques or glacial valleys, sawtooth spine-like ridge or wall of bedrock separating two glacial valleys or cirques

lake effect

Lakes can also cause a downwind increase in precipitation—snow or rain generated by the lake effect, in which storms either pick up more moisture from the lake or undergo uplift as they move over a relatively warm body of water

valley train

Often resembling an alluvial fan confined by valley walls, the depositional landform composed of glacial outwash left by braided streams

wave height

The vertical distance between a trough and the adjacent crest

col

a glacially eroded pass between two mountain valleys, a pass formed when headward erosion causes two cirques to intersect, producing a low saddle in a high mountain ridge or arêt

The Superior Upland

a highland of resistant rock, caused the front of the glacier to split into two masses, called lobes, diverting the southward-flowing ice around this topographic obstruction

oxbow lake

a lake or pond found in a meander cut-off on a floodplain

esker

a long and narrow ridge composed of glaciofluvial sands and gravels that in map view winds or meanders along, narrow, winding ridge of coarse sediment probably deposited in association with a meltwater tunnel at the base of a continental glacier, probably formed by meltwater streams flowing in ice tunnels at the base of ice sheets, Many eskers are mined for their sand and gravel, Being natural embankments, they are frequently used in marshy, glaciated landscapes as places to build roads. Eskers are especially well developed in Sweden, Finland, and Russia

dimensional analysis

analysis of the measurement units

rock flour

clay-sized crushed rock

lagoons

coastal embayment of water that is blocked from free circulation with the ocean or lake by a landform barrier, Salinity in the lagoon varies from that of the open water body, depending on freshwater inflow and evaporation, and affects organisms living in the lagoon

Glacial till

consists of an unsorted, unstratified, rather jumbled mass of gravel, sand, silt, and clay

ocean

covers 71% of Earth's surface

perennial flow

describes streams that conduct flow continuously all year

radial

drainage pattern develops where streams flow away from a common high point on cone- or dome-shaped geologic structures, such as volcanoes

Ephemeral lakes

evaporate and disappear only to reappear when rain provides another episode of inflow

ground moraine

irregular, hummocky landscape of till deposited on Earth's surface by a wasting glacier

Kame terraces

landforms resulting from accumulations of glaciofluvial sand and gravel along the margins of ice lobes that melted away in valleys of hilly regions, Good examples of kame terraces can be seen in New England and New York

degradation

landscape lowering that results from more erosion than deposition over time

Pediments

lie along the base of some mountains, particularly in the tectonically less active areas of exterior drainage beyond the southern boundary of the Great Basin

Arcuate deltas

like that of the Nile River, project to a limited extent into the receiving water body and have a smooth laterally continuous seaward edge, shape of arcuate deltas shows moderate reworking of the fluvial deposits by waves and currents—much more so than in the case of the bird's-foot delta

tarns

mountain lake in a glacial cirque

The Hawaiian Islands

moving northwestward with the Pacific plate and will slowly submerge. A new volcanic Hawaiian Island, named Loihi, is forming to the southeast

inselbergs

remnant bedrock hill or mountain rising above a stream-eroded plain or pediment in an arid or semiarid region, Resistant knobs of the bedrock that remain projecting up above the surface of some pediments

sea stack

resistant pillar of rock projecting above water close to shore along an erosion-dominated coast, When the top of an arch collapses or a sea cliff retreats and a resistant pillar is left standing

Tsunamis

result from the sudden displacement of water by movement along faults, landslides, volcanic eruptions, or other impulsive events, builds to dangerous heights in shallow coastal waters, long-wavelength waves that form when a large mass of water displaced upward or downward by an earthquake, volcanic eruption, landslide, or other sudden event works to regain its equilibrium condition, As the long-wavelength waves approach the shallow water of a coastline, their height can grow substantially, the most dangerous type of wave affecting coastal areas, As a wave moves into shallow coastal water, its speed decreases but its height increases

Sea arches

result where two caves meet from each side of a headland

coastal cliff erosion

second major source of coastal sediment

sea

steep, choppy, chaotic waves still forming under the influence of a storm

tributaries

stream channel that delivers its water to another, larger channel

Alluvial fans and playas

tend to occur in mountain and basin deserts of active tectonism, which typically have interior drainage

Wavelength

the horizontal distance between successive wave crests

interfluve

the land between two stream channels

trunk stream

the larger channel in which smaller streams contribute their water and sediment

stream competence

the largest particle size that a stream can carry; varies with a stream's velocity

drainage density

the length of stream channels per unit area of the drainage basin

discharge

the volume of water flowing past a given point per unit time

Oceanic islands

volcanic island that rises from the deep ocean floor, volcanoes that rise from the deep-ocean floor and are geologically related to oceanic crust, not the continents, Most oceanic islands, such as the Aleutians, Tonga, and the Marianas, occur in island arcs along the edges of the trenches. Others, like Iceland and the Azores, are peaks of oceanic ridges rising above sea level. Many oceanic islands, like the Hawaiian Islands, occur in chains. The oceanic crust sliding over a stationary "hot spot" in the mantle causes these island chains

Stream discharge

volume of water flowing past a point (cross section) in a stream channel in a given unit of time, most commonly expressed in units of cubic meters per second or cubic feet per second, Discharge data indicates the size of a stream and, in times of excessive flow, provide an index of flood severity, streams in larger drainage basins have greater discharge and are longer than streams in smaller drainage basins, Among the major rivers of the world, the Amazon has by far the largest drainage basin and the greatest discharge; the Mississippi River system is ranked fourth in terms of discharge, discharge is determined not by measuring Q=v/t directly but by using the fact that discharge (Q) is also equal to the area of the cross section (A) times the average stream velocity (v)

Breakwaters

walls built parallel to the shoreline in the breaker zone. Large waves expend the bulk of their energy breaking on the structure, thus limiting the amount of beach erosion

wave base

water depth equal to half the length of a given wave; at smaller depths the wave interacts with the underwater substrate, the depth L/2, Waves begin to "feel bottom" when the water depth decreases to half the distance between wave crests, As depth gets smaller, the wave velocity and wavelength decrease while the wave height and steepness increase until breaking occurs, As they approach the coast and enter shallower water, d < L/2, friction with the bed causes the waves to undergo a decrease in both velocity and wavelength

mixed tide pattern

A third type of tidal pattern consists of two high tides of unequal height and two low tides, one lower than the other., the waters of the Pacific coast of the United States exhibit this

seif

A type of large longitudinal dune, a large, long, somewhat sinuous sand dune elongated parallel to the prevailing wind direction, found in the deserts of Arabia and North Africa, huge, sinuous (rather than linear), sharp-crested dunes, sometimes hundreds of kilometers long, whose troughs are almost free of sand. They attain heights up to 180 meters (600 ft)

Wind Deposition

All materials transported by the wind are eventually deposited whenever and wherever the wind energy falls below the minimum amount needed to keep the grains moving, Fine-grained particles (silts and clays) are often transported in suspension long distances from their source area before being deposited, sometimes quite thickly, as a blanket covering the preexisting topography. In comparison, the coarser, sand-sized particles, transported in saltation and surface creep, accumulate much closer to their source area

longshore current

Another outcome of an incompletely refracted oblique wave is that when the crest arrives at the break point at one location, farther along the beach in the direction the waves are traveling, that same position relative to the shoreline is occupied by a wave trough. This difference in water level initiates a current of water, called the longshore current, flowing parallel to the shoreline near the breaker zone

beach nourishment

Another strategy has been to add sediment to the beach artificially by dredging harbors or reservoirs and trucking or pumping that sediment through pipes to the beach

isostatic rebound

As the ice receded and its weight on the land was removed, the land rose by the process of isostatic rebound

saltation (wind)

As with fluvial transportation, particles that are too large to be carried in eolian suspension are bounced along the ground as part of the bed load in the transportation process, When particles moving in eolian saltation, which are typically sand sized, bounce on the ground, they generally dislodge other particles that are then added to the wind's suspended or saltating load

glacier's head

At the farthest upslope edge of an alpine glacier, the upslope end of the zone of accumulation, It abuts the steep bedrock cliff that comprises the cirque headwall

cuspate deltas

Coastal processes play a strong role in their formation by pushing the sediments back toward the mainland and reworking them into beach ridges on either side of the river mouth. An example of a cuspate delta is the São Francisco in Brazil

terminal moraines

End moraines that mark the farthest advance of a glacier

tsunameters

The U.S. National Oceanic and Atmospheric Administration (NOAA) has established an array of instruments (tsunameters) to monitor pressure and temperature on the ocean floor and convert these data to water column height, The array constitutes an important part of a growing international tsunami monitoring network

caprock

The cliff-forming, resistant, horizontal rock layer that forms the top of, or caps, the sequence of horizontal layers of alternating resistant and erodible rock, top plateaus and constitute canyon rims

zone of accumulation

The colder, snowier upslope portion of a glacier, where annual accumulation (input) exceeds annual ablation (output), the higher elevation part of a glacier; where more frozen water is added than removed during the year

tidal range

The difference in sea level between high tide and low tide, varies from place to place in response to the shape of the coastline, water depth, access to the open ocean, submarine topography, and other factors,

second-order stream

Two first-order streams must meet to form this, larger than each of the first-order streams

Stream Hazards

Variability of stream flow constitutes the greatest problem for life along rivers and is also an impediment to their use

Base Level Changes

Variations in base level for basins of exterior drainage result principally from climate change, A drop in base level causes downcutting and a rise causes deposition

mouth

Water in a stream system proceeds downslope through a succession of channels of ever-increasing order toward the downstream end, or mouth, of the stream

glacial ice

When the ice is deep enough and has a density up to about 0.9 gram per cubic centimeter, Pressure from burial under many layers of snow, firn, and ice causes the glacial ice below to become plastic and flow outward or downward away from the area of greatest snow and ice accumulation

Icefall

Where a glacier locally flows over a steep descent, such as over a subglacial cliff, an icefall develops in the brittle upper zone, intersecting crevasses break the brittle ice into a morass of unstable blocks that ride on rapid flowing ice below. Icefalls and crevasses are extremely dangerous areas for anyone venturing onto the ice, the glacial equivalent of rapids or waterfalls in a river and are riddled with crevasses that break the ice into huge, unstable blocks

geologically stable deserts

Where arid climates occur in expansive regions of largely open, low-relief terrain, as in the ancient and geologically stable deserts of Australia and the Sahara, common landforms include inselbergs surrounded by extensive desert plains; deflation hollows; playas; washes; the channels of ancient streams; and the beds of shallow, ancient lakes. With limited terrain roughness, areas of large longitudinal dunes can develop in these settings

piedmont alluvial plain

Where extensive fans coalesce over very wide areas, a plain created by stream deposits at the base of an upland, such as a mountain, a hilly region, or a plateau, like the area surrounding Phoenix, Arizona, generally have rich soils and the potential to be transformed into productive agricultural lands

sea caves

Where the cliffs are well jointed but cohesive, wave erosion can create sea caves along the lines of weakness

medial moraine

Where two tributary valley glaciers join, their lateral moraines merge downflow creating a medial moraine in the center of the trunk glacier, a central moraine in a large valley glacier formed where the interior lateral moraines of two tributary glaciers merge, cause the characteristic dark stripes seen on the surface of many alpine glaciers

salt-crust playas

also known as salt flats, receive much of their water from groundwater, are damp most of the time, and are encrusted with salt mineral deposits crystallizing out of the evaporating groundwater, an ephemeral lake bed composed mostly of salt minerals, Some salt-crust playas are the floors of the desiccated ancient lakes that existed in now-desert basins when they experienced more moderate climates in the recent geologic past

piedmont glaciers

an alpine glacier that extends beyond a mountain valley spreading out onto lower flatter terrain, when the ice extends to lower elevations beyond the mouth of a canyon, where the ice spreads out over more open terrain

valley glaciers

an alpine glacier that extends beyond the zone of high mountain peaks into a confining mountain valley below, Alpine glaciers that occupy former stream valleys

reservoirs

an artificial lake impounded behind a dam

recessional moraine

an end moraine deposited as a consequence of a temporary pause by a retreating glacier

clay pan

an ephemeral lake bed composed mostly of fine-grained clastic particles, playas that receive most of their water from surface runoff typically have a smooth clay surface, sometimes called a clay pan, that is hard when dried out by the desert sun but extremely gooey and slippery when wet

washes

an ephemeral stream channel in an arid climate, also known as arroyos in the southwestern United States and wadis in North Africa and southwestern Asia, these channels usually form where rushing surface waters cut into unconsolidated sediment or easily eroded rock, typically gravelly and braided channels, prone to flash floods, which makes them potentially dangerous sites

channel roughness

an expression of the frictional resistance to stream flow due to irregularities, such as those from large rocks and vegetation sticking up into the flow, in a stream channel bed and sides, causes a considerable decrease in stream energy because of the frictional effects

sand seas

an extensive area covered by sand dunes

sand sheet

an extensive uniform cover of wind-deposited sand having little or no surface relief

plateau

an extensive, elevated region with a fairly flat upper surface, an extensive, flat-topped landform or region characterized by relatively high elevation, but low relief, consist of tectonically uplifted horizontal rock layers, many exist in the desert and semiarid regions of the world, including the extensive tectonically uplifted Colorado Plateau, centered on the Four Corners area of Arizona, Colorado, New Mexico, and Utah, In such desert plateau regions, streams responded to the uplift by cutting narrow, steep-sided canyons, Where the canyon walls consist of horizontal layers of alternating resistant and erodible rocks, differential weathering and erosion create stair-stepped walls, with near-vertical cliffs made from resistant rock layers (ordinarily sandstone, limestone, or basalt) and weaker strata (often shales) forming gentler slopes

barrier spit

a barrier beach attached to the mainland at one end like a spit, but enclosing a lagoon, originated as a spit and thus is attached to the mainland at one end but has extended almost completely across the mouth of an embayment to restrict the circulation of water between it and the ocean or lake

Weathering

an important factor in the breakdown of rocks in the coastal zone, as in other environments, preparing pieces for removal by wave erosion, Water is a key element in most weathering processes, and in addition to normal precipitation, rocks near the shoreline are subjected to spray from breaking waves, high relative humidities, and condensation

roches moutonnées

bedrock hill subjected to intense glacial abrasion on its up-ice side, with some plucking evident on the down-ice side, caused by abrasion and plucking at the base of a glacier, asymmetric bedrock hills or knobs that are smoothly rounded on the up-ice side by abrasion, with plucking evident on the abrupt down-ice side

meander cut-offs

bend of a meandering stream that has become isolated from the active channel, occur when a stream seeks a shorter, steeper, and straighter path; breaches through the levees; and leaves a former meander loop isolated from the new channel position

marine terraces

abrasion platform that has been elevated above sea level and thus abandoned from wave action

offshore zone

accounts for the remainder of the standing body of water, that part lying seaward or lakeward of the outer edge of the breaker zone

Sandstorms

can occur in areas where sand-sized sediment is abundant at the surface, Because sand grains are larger and heavier than silts and clays, most sandstorms are restricted to a zone near the ground, where objects are severely abraded by the abundant saltating sand

Sea cliffs

carved where waves pound directly against steep land, If a steep coastal slope continues deep beneath the water, it may reflect much of the incoming wave energy until corrosion and hydraulic action eventually take their toll on the rock

paternoster lakes

chain of lakes connected by a postglacial stream occupying the trough of a glaciated mountain valley

yardang

aerodynamically shaped remnant ridge of wind-eroded bedrock or partly consolidated sediments, a wind-sculpted remnant ridge, often of easily eroded rock or semilithified sediments, left behind after the surrounding material has been eroded by abrasion, abrasion and deflation are most effective where rocks are soft or weak

Active dunes

change their shape and advance downwind as a result of wind action, Many active dunes travel, or migrate, when wind-eroded sand from their upwind (windward) slope moves by saltation and surface creep over the dune crest and onto the steep leeward (downwind) slope

Velocity

decreases over time when flow subsides—for example, after the impact of a storm—but it also varies from place to place along the stream, A distinctly shallower part of a channel cross section that lies far from the deepest and fastest flow typically experiences low flow velocity and becomes the site of recurring deposition

fjords

deep, glacial trough along the coast invaded by the sea after the removal of a glacier, The fjords of Scotland, Norway, Iceland, and New Zealand show that glaciers in those regions reached the sea during the Pleistocene

cirques

deep, sometimes steep-sided amphitheater formed at the head of an alpine valley by glacial ice erosion, eroded by the ice near high peaks at valley heads

point bar

deposit of alluvium found on the inside of a bend in a meandering stream channel, stream deposits in the low velocity and shallow flow on the inside of the meander bends

ice shelves

enormous flat-topped plates of ice attached to land along at least one side, large, flat-topped plate of ice overlying the ocean but attached to land; a source of icebergs, the icebergs in Antarctic waters do not have the irregular surface form of Greenland's icebergs

Deflation

entrainment and removal of loose surface sediment by the wind, similar to the hydraulic force of running water, occurs when wind blowing fast enough or with enough turbulence over an area of loose sediment is able on its own to pick up and remove small fragments of rock

abrasion

erosion process in which particles being carried by a geomorphic agent are used as tools to aid in eroding more Earth material, a process even more powerful than hydraulic action

Hydraulic action

erosion resulting from the force of moving water, refers to the physical, as opposed to chemical, process of stream water alone removing pieces of rock

Kettle lakes

form where large, discrete blocks of ice buried or partly buried in glacial deposits, melt away leaving a depression

Rip currents

relatively narrow zones of strong, offshore-flowing water that occur along some coastal areas, strong, narrow surface current flowing away from shore. It is produced by the return flow of water piled up near shore by incoming waves, a means for returning broken wave water from the nearshore zone back to deeper water, frequently visible as streaks of foamy, turbid water flowing perpendicular to the shore

braided channels

in which multiple threads of flow split and rejoin around temporary deposits of coarse-grained sediments, are common in deserts, works to carry its extensive bed load

glacial deposits

include clastic sediments of a wide range of sizes, frequently mixed with layers of plant matter and soil

ventifacts

individual wind-fashioned stones, rock displaying distinctive wind-abraded faces, pits, grooves, and polish, a rock that has been trimmed back to a smooth slope on one or more sides by sandblast, Ventifacts subjected to multiple sand-transporting wind directions have multiple faces, called facets, which meet along sharp edges

pedestaled, or balanced, rock

result from various physical and chemical weathering processes in the damper environment at the base of an exposed rock and are not usually related to eolian abrasion

ripples

small (centimeter-scale) wave forms in water or sediment, Grains moving along the ground in surface creep

Suspended load

solid particles that are small enough to be transported considerable distances while remaining buoyed up in a moving air or water column, consists of the small clastic particles being moved in suspension, The intense weathering in humid regions produces much fine-grained sediment that is incorporated into streams as suspended load

Glacier flow

rates vary from imperceptible fractions of a centimeter per day to as much as 30 meters (100 ft) per day. Glaciers flow more rapidly where the slope is steeper, ice is thicker, and temperatures are warmer, temperate alpine glaciers, like the Nisqually Glacier, flow much faster than cold polar continental glaciers

wave steepness

ratio of wave height to wavelength for a given wave

Desert climates

receive small amounts of precipitation and they experience high rates of potential evapotranspiration, when rainfall does occur, much of it falls on impermeable surfaces, producing intense runoff, often generating flash floods, and operating as a powerful agent of erosion

glaciation

refers to the existence and actions of moving ice as well as its effects on the landscape

Drainage area

refers to the measured extent of a drainage basin and is typically expressed in square kilometers or square miles

dissolved load

soluble minerals or other chemical constituents carried in water as a solution, ions of rock material held in solution, more common in basins with high amounts of infiltration and base flow because slow-moving groundwater that feeds base flow acquires ions from the rocks through which it moves

gullies

steep-sided stream channel somewhat larger than rills that even in humid climates flow only in direct response to precipitation events, depth and width may approach as much as a couple of meters

braided channels

stream channel composed of multiple subchannels of simultaneous flow that split and rejoin and frequently shift position, result from an abundant bed load of coarse sediment, when the stream sets down part of its coarse load, the water splits and flows around the deposit, eventually separating the main stream into numerous strands

continental shelves

the gently sloping margin of a continent overlain by ocean water, the edges of the continents and which currently lie below sea level

spring tide

the larger than average tidal range that occurs during new and full moon, The increased tidal range caused by the alignment of Earth, the moon, and the sun, occurs every 2 weeks

angle of repose

the steepest slope that a pile of dry, loose material can maintain without experiencing slipping, sliding, or flow down the slope—is about 34* for sand

hanging valleys

tributary glacial trough that enters a main glaciated valley at a level high above the valley floor, Bridalveil Falls in Yosemite National Park cascades off the floor of a U-shaped hanging valley toward Yosemite Valley below

interior drainage

Desert drainage basins characterized by streams that terminate in closed interior depressions, The Humboldt River in Nevada is an outstanding example; after rising in the mountains of central Nevada and flowing 465 kilometers (290 mi), the river disappears into the Humboldt Basin, a closed depression

drumlin fields

Drumlins are usually found in swarms, called drumlin fields, with as many as a hundred or more clustered together

crests

During and just after a runoff-producing rainfall, the stream level rises in response to the increased discharge. The water level peaks, or crests, at the time of maximum discharge and then falls as the river eventually returns to a more average amount of flow. At a gaging station, the rise, peak, and fall in discharge over time are recorded as a climbing, peaking, and then descending curve on the hydrograph

deflation hollows

Erosion by deflation can produce shallow depressions in a barren surface of unconsolidated materials, vary in diameter from a few centimeters to a few kilometers, a wind-eroded depression in an area not dominated by wind-deposited sand, particularly common in non-mountainous arid regions, tend to collect rainwater and may hold water for a time, depending on permeability and evaporation rates, deflation hollows, like bolsons, frequently contain playas, often form at sites that were already exhibiting a slight depression or where vegetation cover has been breached by overgrazing, fire, or other means

primary coastlines

Erosional and depositional processes of the land dominate, coast that has developed its present form primarily from land-based processes, especially fluvial and glacial processes, result from such rapid changes in the position of the shoreline that coastal processes are not able to have a significant landforming effect, The major types of primary coastlines (with examples) are drowned river valleys (Delaware and Chesapeake Bays), glacial erosion coasts (southeastern Alaska, British Columbia, Puget Sound in Washington, and from Maine to Newfoundland), glacial deposition coasts (Cape Cod, Massachusetts, and the north shore of New York's Long Island), river deltas (Mississippi Delta, Louisiana), volcanic coasts (Hawaii), and faulted coasts (California)

glaciolacustrine deposits

Evidence for many lakes that no longer exist is found in the widespread occurrence of glaciolacustrine (glacial, ice; lacustrine, lake) deposits that allow us to reconstruct the extent and determine the age of those lakes

Basin and Range region

Fault-block mountains in the Basin and Range region rise thousands of meters above the desert basins, and many form continuous range. These high ranges, such as the Guadalupe Mountains, Sandia Mountains, Warner Mountains, and the Panamint Range, to name just a few, encourage orographic rainfall. Fluvial erosion dissects the mountain blocks to carve canyons between peaks and cut washes between interfluves

Atoll Dangers

First, they have a low elevation above sea level and provide no defense against huge storm waves and tsunamis that can inundate the entire atoll, drowning all its inhabitants. Rising sea level due to global warming also threatens these low islands. Second, there is little freshwater available on the porous coral limestone surface. Third, little vegetation can survive in the lime-rich rock and soil of the atoll islands. The coconut palm is an exception, and coconuts were vital to the survival of early inhabitants of the atoll islands in Polynesia and Micronesia.

Stream Energy

Friction along the bottom and sides of a channel and even between the stream surface and the atmosphere slows down the stream velocity and therefore contributes to a decrease in stream energy, maximum velocity occurs somewhat below the stream surface at the deepest part of the cross section, streams lose energy because of internal friction in the flow related to eddies, currents, and the interaction among water molecules, About 95% of a stream's energy is consumed in overcoming all types of frictional effects

bergschrund

Ice within an alpine glacier flows downslope from the zone of accumulation to the zone of ablation. This downslope movement is sometimes evidenced by a large crevasse, known as a bergschrund, that may develop between the head of the glacier and the cirque headwall, Presence of a bergschrund shows that the ice mass is pulling away from the confining rock walls of the cirque

net accumulation

If a glacier received more input of frozen water (accumulation) during a year than was removed from it (ablation) that year, The result of net accumulation is a larger glacier, and as alpine glaciers grow they advance; that is, their toes extend farther downvalley

entrenched

If new uplift occurs gradually in an area where stream meanders have formed, these meanders may become entrenched as the stream deepens its valley, instead of eroding the land laterally, with meanders migrating across an alluvial plain, the rejuvenated stream's primary activity is vertical incision

Elwha River

In 2014, the largest dam removal in American history to date, flushing of the sediment that had accumulated in the reservoirs was allowed to proceed naturally, accompanied by extensive revegetation of the dam and reservoir areas with native plant species

abrasion (wind)

In eolian abrasion, particles already being transported by the wind strike rocks or sediment and break off or dislodge additional rock fragments, Wind-driven solid particles are more effective than the wind alone in dislodging and entraining other grains and in breaking off new fragments of rock, Most eolian abrasion is quite literally sandblasting, and quartz sand, which is common in many desert areas, can be a very effective abrasive agent in eolian processes, limited to a zone close to ground level

Lake Missoula

In northern Idaho, a glacial lobe moving southward from Canada blocked the valley of a major tributary of the Columbia River, creating an enormous ice-dammed lake known as Lake Missoula, On occasions when the ice dam failed, Lake Missoula emptied in tremendous floods that engulfed much of eastern Washington. The racing floodwaters scoured the basaltic terrain, producing Washington's channeled scablands, which consist of interweaving steep-sided troughs (coulees), dry waterfalls, scoured-out basins, and other features quite unlike those associated with normal stream erosion, particularly because of their gigantic size

moraines

Landforms constructed from glacial deposits, typically ridges of till along these margins of glaciers

eolian

Landforms—whether in the desert or elsewhere—that are created by wind, pertaining to the land-forming work of the wind

erratics

Large boulders scattered in and on the surface of glacial deposits or on glacially scoured bedrock are called erratics if the rock they consist of differs from the local bedrock, large glacially transported boulder deposited on top of bedrock of different composition, known to be of glacial origin because they are marked by glacial striations and are found only in glaciated terrain, can occur in association with alpine glaciers, but they are better known and more impressive when deposited by ice sheets, which have moved boulders weighing hundreds of tons over hundreds of kilometers

glaciers

Large masses of flowing ice, a large mass of ice that flows as a plastic solid, are excellent climate indicators because certain environmental conditions are required for glaciers to exist and they respond visibly to climate variation, Their long-term storage of freshwater as ice has a tremendous impact on the hydrologic cycle and the oceans, and the accumulation of ice by glaciers provides a record of past climates that can be studied from ice cores, an effective and spectacular geomorphic agent on major portions of Earth's surface, masses of flowing ice that have accumulated on land in areas where the annual input of frozen precipitation, especially snowfall, has exceeded its yearly loss by melting and other processes, open systems with input, storage, and output of material, are an important part of Earth's hydrologic cycle and are second only to the ocean in the amount of water they contain, Approximately 2.25% of Earth's total water is currently frozen in glaciers. This frozen water, however, makes up about 70% of the world's freshwater, with the vast majority stored on Greenland and Antarctica

bed load

Larger particles that saltate or move in traction along the streambed, solid particles moved by wind or water by bouncing, rolling, or sliding along the ground or streambed, Streams dominated by bed load tend to occur in arid regions because of the limited weathering rate in arid climates, If a stream has a high proportion of bed load in relation to its discharge, it deposits much of its load as sand and gravel bars in the streambed

glacial trough

Little Cottonwood Canyon, a U-shaped valley carved by glacial erosion, a glacier's tendency to flow straight ahead rather than to meander causes it to straighten out the preexisting valley that it occupies

longitudinal dunes

Long dunes aligned parallel to the average wind direction, a linear ridge-like sand dune that is oriented parallel to the prevailing wind direction, no consistent distinction between the back slopes and slip faces of these dunes, and their summits may be either rounded or sharp, Strong winds are important to the formation of most longitudinal dunes, which do not migrate but instead elongate in the downwind direction

load

Materials transported by streams, enter the stream system by erosion and mass movement, particularly in upstream locations, exits the stream system at the river mouth

tributary glaciers

Most large valley glaciers have smaller tributary glaciers. Like the main ice stream, tributary glaciers also carve U-shaped valleys, or troughs, During peak glacial phases, the surface of a tributary glacier merges smoothly with that of the trunk glacier, Tributary glacial troughs tend to be smaller and not as deep as the trough of the main glacier

Wave abrasion

Once clastic particles are in motion, waves have solid tools to use to perform even more work through the grinding erosive process of abrasion. Abrasion is the most effective form of erosion by each of the geomorphic agents, including waves.

Glacial Abrasion

Once load is entrained at the base and sides of the ice, moving glaciers are armed with clastic particles that are very effective tools for scraping and gouging out more rock material by the erosional process of abrasion, Bedrock obstructions subjected to intense glacial abrasion are typically smoother and more rounded than those produced by plucking, Unlike the situation with liquid water in streams, volume and velocity of flow do not directly determine the particle sizes that plastically flowing, solid ice can erode and transport

Coastal erosion

Rates of coastal erosion are controlled by the interaction between wave energy and rock type, greatly accelerated during high-energy events, such as severe storms and tsunamis

Coastal Deposition

Significant amounts of sediment accumulate along coasts where wave energy is low relative to the amount or size of sediment supplied, Amount and size of sediment supplied to the coastal zone vary with rock type, weathering rates, and other elements of the climatic, biological, and geomorphic environment, 3 main sources of sediment: streams, coastal cliff erosion, and sediment from offshore sources

kettles

Small depressions or pits, called kettles, mark some outwash plains, till plains, and moraines, depression formed by the melting of an ice block buried in glacial deposits left by a retreating glacier, Kettles represent places where blocks of ice were originally buried in glacial deposits. When the blocks of ice eventually melted, they left surface depressions, and many kettles now contain kettle lakes. For example, most of Minnesota's famous 10,000 lakes are kettle lakes. Some kettles occur in association with alpine glacial deposits, but the vast majority are found in landscapes that were occupied by ice sheets or ice caps

ice-marginal lakes

Some lakes formed along the front of the Pleistocene ice sheets in areas where glacial deposits disrupted the surface drainage or where a glacier prevented depressions from being drained of meltwater. These lakes usually accumulated where water became trapped between a large end moraine and the ice front or where the land sloped toward, instead of away from, the ice front. In both situations, ice-marginal lakes filled with meltwater. They drained and ceased to exist when the retreat of the ice front uncovered an outlet route for the water body, During their existence, fine-grained sediment accumulated on the floors of these ice-marginal lakes, filling in topographic irregularities

differential erosion

The effects of differential erosion can be significant in the upper course if the stream cuts through rock layers of varying resistance. The stream will have a steeper gradient where it flows over more resistant rock than where it encounters weaker rock. A steep gradient gives the stream flow more energy, which the stream needs so that it can erode the resistant rock. Rapids and waterfalls often mark the location of resistant materials in a stream's upper course. Where rocks are particularly resistant to weathering and erosion, valleys are narrow, steep-sided gorges or canyons; where rocks are less resistant, valleys tend to be more spacious.

Wisconsinan stage

The geomorphic effects of the last major glacial advance, known in North America as the Wisconsinan stage, are the most visible in the landscape today, The glacial landforms created during the Wisconsinan stage, which ended about 10,000 years ago, are relatively recent and have not been destroyed to any great extent by subsequent geomorphic processes. Consequently, we can derive a fairly clear picture of the extent and actions of the ice sheets and ice caps, as well as alpine glaciers, at that time

Dust Bowl

The infamous Dust Bowl era of the 1930s particularly affected the southern Great Plains of the United States in this way when devastating dust storms were brought about by years of drought without adequate modification of agricultural practices

location of the equilibrium line

The interaction between latitude and elevation, both of which affect temperature, is an important factor, On mountains near the equator, the equilibrium line lies at very high elevations. Elevation of the equilibrium line decreases with increasing latitude until it coincides with sea level in the polar regions, With colder temperatures and greater snowfall, the equilibrium line will decrease in elevation; it retreats to higher elevations if the climate warms, insolation: A shady mountain slope will have a lower equilibrium line than one that receives more insolation. Wind is another factor because it produces snowdrifts on the leeward side of mountain ranges

Finger Lakes of New York

The lakes occupy linear, glacially eroded basins excavated during the Pleistocene, examples of lakes that have accumulated in elongated, ice-deepened basins

playa

The lowest part of most bolsons, dry lake bed in a desert basin; typically fine-grained clastic (clay pan) or saline (salt crust), the fine-grained bed of an ephemeral lake, Mineral companies extract the rich deposits of evaporite minerals—including such important industrial chemicals as potassium chloride, sodium chloride, sodium nitrate, and borates—that have been deposited in some playa beds

Lower Stream Course

The minimal gradient and close proximity to base level along the ideal lower river course make downcutting virtually impossible, Stream energy, now derived almost exclusively from the higher discharge rather than the downslope pull of gravity, leads to considerable lateral shifting of the stream channel and creation of a large depositional plain

beach

The most common landform of coastal deposition, a wave-deposited feature that is contiguous with the mainland throughout its length, In settings with high wave energy, particles tend to be larger and beaches tend to be steeper than where wave energy is low, In the midlatitudes, beaches are generally narrower, steeper, and composed of coarser material in winter than they are in summer. The larger winter storm waves are more erosive and destructive, whereas the smaller summer waves, which often travel from the other hemisphere, are depositional and constructive, act as buffers to help protect the land behind them from wave erosion

semidiurnal tidal regime

The most common tidal pattern approaches the ideal of two high tides and two lows in a tidal day, characteristic along the Atlantic coast of the United States, but it does not occur everywhere

fluvial geomorphology

The study of flowing water as a land-shaping process, together with the study of the resulting landforms, the study of streams as land-forming agents, includes the action of channelized and unchannelized flow moving downslope because of the pull of gravity

beach building

The technology involves transferring millions of cubic meters of sand from offshore to replenish existing beaches or build new ones where beaches have eroded away. Huge barge-mounted dredges dig sand from the sea bottom near the shore, and the sand is pumped as a slurry through massive movable tubes to be deposited on a beach, price is paid in destroyed natural beach environments, reduced offshore water quality, eliminated or displaced species, and repeated damage to food chains for coastal wildlife each time a beach is rebuilt

butte

Through additional erosion of the caprock from all sides, a mesa is reduced to a butte, which is a similar, flat-topped erosional remnant but with a smaller surface area, isolated erosional remnant, a hill with a flat summit formed by a caprock and is often bordered by steep-sided escarpments. Buttes are usually found in arid regions of flat-lying sediments and are somewhat taller than they are wide

Glacial Ice

Through time, the layers of low-density snow become layers of much denser solid ice. Some of this change is the result of compaction, but pressure also causes some melting and refreezing of the ice, The temperature at which ice melts is O*C at atmospheric pressure, but ice can melt at lower temperatures if it is under enough pressure, Both compaction and pressure melting and refreezing work to reduce the amount of air in the frozen mass and thereby increase the material's density, The denser the ice, the bluer it appears

lateral moraines

Till deposited as ridges paralleling the side margins of a glacier

Barrier islands

a barrier beach constructed parallel to the mainland, but not attached to it; separated from the mainland by a lagoon, common features of low-relief coastlines, dominate the Atlantic and Gulf coasts of the United States from New York to Texas. Some excellent examples of long barrier islands are Fire Island (New York), Cape Hatteras (North Carolina), Cape Canaveral and Miami Beach (Florida), and Padre Island (Texas), Rising sea level since the Pleistocene appears to have played a major role in the formation of barrier islands. They migrate landward over long periods and may change drastically during severe storms, especially hurricanes

baymouth barrier

a barrier beach that extends across the mouth of an embayment, attached to the mainland at both ends, to form a lagoon, If the barrier spit crosses the mouth of the embayment to connect with the mainland at both ends, Limited connection is maintained between the lagoon and the main water body through a breach or inlet cut across the barrier somewhere along its length

till plain

a broad area of low relief covered by continental glacier deposits, often accumulates to depths of 30 meters (100 ft) or more, Because of the uneven nature of deposition from the wasting ice, the topographic configuration of the till-covered land varies from place to place. In some areas, the till is too thin to hide the original contours of the land, whereas in other regions, thick deposits of till make broad, rolling plains of low relief. Small hills and slight depressions, some filled with water, characterize most till plains, reflecting the uneven glacial deposition. The gently rolling till plains of Illinois and Iowa are excellent examples of this glacial landform

barrier beaches

a category of elongate depositional coastal landforms that lie parallel to the mainland but separated from it by a lagoon, act to protect the mainland from direct wave attack, Like beaches and spits, barrier beaches have a submerged part and a portion that is always above water, except in extreme storm conditions or extremely high tide

bajada

a continuous ramplike slope of alluvium created when alluvial fans become so large that adjacent fans join along their side, consists of adjoining alluvial fans that have coalesced to form an "apron" of alluvium along the mountain base, an extensive intermediate slope of adjacent, coalescing alluvial fans connecting a steep mountain front with a basin or plain

Gravel

a general term for any sediment larger in size than sand

cirque glaciers

a generally small alpine glacier restricted to a high-elevation basin (cirque), the smallest type of glacier, Alpine glaciers begin as cirque glaciers at the start of an ice age, become valley glaciers when they expand into the valley below the cirque, and may eventually become piedmont glaciers as the ice age intensifies. Most cirque glaciers today represent small remnants of previously larger alpine glaciers, often deposit a ridge of till at the down-ice edge of the cirque, and this accentuates the bowl-shaped appearance

star dunes

a large pyramid-shaped sand dune with multiple slip faces resulting from convergent wind directions, have a pyramidal shape in which ridges of sand radiate out from a high center point to resemble a star in map view, most common in areas where there is a great quantity of sand, changing wind directions, and an extremely hot and dry climate, dunes are stationary, but ridges and slip faces shift orientation with wind variations

The Great Basin

a large subregion centered on Nevada and characterized by interior drainage, numerous alternating mountain ranges and basins, and active tectonism—occupies much of the central and northern part of the Basin and Range

Transverse dunes

a linear ridge-like sand dune that is oriented at right angles to the prevailing wind direction, created where sand-transporting winds blow from a constant direction and the supply of sand is abundant, As with barchans, the upwind slope of a transverse dune ridge is gentle, and the steeper downwind slip face lies at the angle of repose, In the downwind direction, transverse dunes form ridge after ridge separated from each other by low swales in a repeating wavelike fashion, Abundant sand supply derives from such sources as easily eroded sandstone bedrock, sandy alluvium deposited by exotic streams or during wetter climates in the Pleistocene Epoch, or sandy deltas and beaches left in the landscape after the desiccation of ancient lakes

Alpine glaciers

a mass of flowing ice that exists in a mountain region due to climatic conditions resulting from high elevation, exist where the precipitation and temperature conditions required for glacier formation result from high elevation, fed by ice and snow in mountain areas and usually occupy valleys that were previously created by stream erosion, the rate of movement is greatest on the glacier surface toward the middle of the ice because this location experiences accumulated movement from layers of plastic flow below and is farthest from frictional resistance encountered along the valley sides

Rias

a narrow coastal embayment that occupies a submerged river valley, created where river valleys are drowned by a rise in sea level or a sinking of the coastal area, these irregular coastlines result when valleys become narrow bays and the ridges form peninsulas, The Aegean coast of Greece and Turkey is an outstanding example of a ria coastline

rills

a narrow stream channel that even in a humid climate conducts flow only during precipitation events, a couple of centimeters deep and a couple of centimeters wide, the smallest rills typically join to form slightly larger rills, which can join to make gullies

headward erosion

a process through which lengthening occurs primarily at the source, is accomplished partly by surface runoff into the stream and partly by springs undermining the slope, The lengthening of a river's course in an upstream direction is particularly important where erosional gullies are rapidly dissecting agricultural land, Channel lengthening also occurs if the path of the stream channel becomes more winding, or sinuous, and this will cause a decrease in stream gradient

notch

a recess, relatively small in height, eroded by wave action along the base of a coastal cliff, Once a recess, or notch, has been carved out along the base of a cliff, weathering and rockfall within the shaded overhang supply clasts that can collect on the notch floor and be used by the water as tools for more efficient erosion by abrasion, Abrasion extending the notch landward leaves the cliff above subject to rockfall and other forms of mass wasting

The Driftless Area

a region in the upper midwestern United States, mainly covers parts of Wisconsin but also sections of the adjacent states of Iowa, Minnesota, and Illinois, This region was not glaciated by the last Pleistocene ice sheets that extended over the rest of the northern Midwest, so it is free of glacial deposits from that time, The landscape of the Driftless Area is very different from the muted terrain and low rounded hills of adjoining glaciated terrain. Narrow stream valleys, steep bluffs, caves, sinkholes, and loess-covered hills produce a scenic landscape with many landforms that would not have survived erosion by a massive glacier, has a unique landscape because of its isolation; it forms, an unglaciated "island" or "peninsula" almost completely surrounded by extensive glaciated regions

temporary base level

a resistant rock layer located somewhere upstream from the river mouth that temporarily controls the lowest elevation of the flow upstream from that point until the stream is finally able to cut down through the resistant layer

end moraine

a ridge of till deposited at the toe or terminus of a glacier, At the toe of a glacier, sediment carried forward by the "conveyor belt" of ice or pushed ahead of the glacier is deposited in a jumbled heap of material of all grain sizes, forming a curved depositional ridge called an end moraine

bar

a shallow, submerged, mounded accumulation of sediment in nearshore locations or in streams, like what forms on the inside of a channel bend

distributaries

a smaller stream that conducts flow away from the larger main channel, especially on deltas; the opposite of a tributary, help direct flow and sediment toward the lake or ocean, Natural levees accumulate along the banks of these distributary channels

glacial period

a span of time characterized by the extensive expansion of glaciers in high latitude and high elevation areas, as well as into the middle latitudes

transverse streams

a stream that flows across the general orientation or "grain" of the topography in a valley that cuts through and across mountains or ridges, Such streams are either antecedent or superimposed

yazoo streams

a stream tributary that flows parallel to the main stream for a considerable distance before joining it, named after the Yazoo River, which parallels the Mississippi River for more than 160 kilometers (100 mi) until it finally joins the larger river near Vicksburg, Mississippi

drumlin

a streamlined ridge or hill, typically about 0.5 kilometer (0.3 mi) in length and less than 50 meters (160 ft) high, molded in glacial drift on till plains, streamlined, elongated hill composed of glacial drift with a tapered end, aligned along the direction of continental ice flow, The broad, steep end faces in the up-ice direction, whereas the gently sloping tapered end points in the direction that the ice flowed; thus the geometry of a drumlin is the reverse of that of roches moutonnées

playa lake

a temporary lake that forms on a playa from runoff after a rainstorm or during a wet season, Direct precipitation onto the playa, inflow from surface runoff, and discharge from the groundwater zone can contribute water to the playa lake, can persist for a day or for a few months, Wind blowing over the playa lake moves the shallow water, along with its suspended and dissolved load, around on the playa surface, helps to fill in any low spots on the playa and contributes to making playas one of the flattest of all landforms on Earth, lose most of their water by evaporation to the desert air

dust storms

a thick, dark, swiftly moving dust cloud that swirls over the land and greatly reduces visibility, sometimes so severe that visibility drops to nearly zero and almost all sunlight is blocked, often highly destructive, removing layers of surface materials in one area and depositing them elsewhere over the course of a few hours

cross section

a thin slice extending from one stream bank straight across the channel to the other stream bank and oriented perpendicular to the channel

outlet glaciers

a valley glacier that flows outward from the main mass of a continental glacier

continental glaciers

a very large and thick mass of flowing ice that exists due to climatic conditions resulting from high latitude, are much larger and thicker than the alpine types, continental glaciers were much more extensive in the Pleistocene Epoch than they are today, at one time covering as much as 30% of Earth's land area

Pleistocene Epoch

an interval of great climate change that began about 2.6 million years ago and ended around 10,000 years before the present, A great number of glacial fluctuations occurred during the Pleistocene, marked by numerous major advances and retreats of ice over large portions of the world's landmasses, At their maximum extent in the Pleistocene, glaciers covered nearly a third of Earth's land surface, North America and Eurasia experienced major glacial expansion during the Pleistocene, In North America, ice sheets extended as far south as the Missouri and Ohio Rivers and covered nearly all of Canada and much of the northern Great Plains, the Midwest, and the northeastern United States

atoll

an island consisting of a ring of coral reefs that have grown up from a subsiding volcanic island and that encircle a central lagoon, ring of coral reefs and islands encircling a lagoon, with no inner island, As a volcanic island subsides, the fringing reef grows upward, keeping pace with the seafloor subsidence, becoming a barrier reef when a lagoon develops and finally an atoll when the only solid material is the outer ring of coral

groin

an obstruction, usually a concrete or rock wall, built perpendicular to a beach to inhibit sediment removal by littoral drifting while the input of sediment from littoral drifting remains the same, This obstruction, however, starves the adjacent, downcoast beach area of material input while the rate of sediment removal from that adjacent beach does not change

accumulation

any addition of frozen water to the mass of a glacier, Most accumulation occurs in winter and consists of snowfall onto a glacier, but there are many ways that frozen water can accumulate, including other forms of precipitation onto the ice, atmospheric water vapor freezing directly onto the ice (gas to solid), and transportation of snow and ice to a glacier surface from surrounding terrain by the wind as snowdrift and by avalanches. Snowdrift has been an important source of frozen water to glaciers in such highlands as the Colorado Rockies and the Ural Mountains in Russia

Deep-water waves

are those traveling through water depth (d) greater than or equal to half the wavelength (L), d ≥ L/2. Traveling waves have no impact on what is below that depth

terminal and recessional end moraines

are usually arc-shaped and convex toward the direction of ice flow, End moraines provide more evidence than just the direction of ice flow. Characteristics of the material deposited in the end moraines also help us detect the sequence of advances and retreats of each successive ice sheet

ice-scoured plains

areas of low, rounded hills, lake-filled depressions, and wide exposures of bedrock, In addition to large expanses of exposed gouged bedrock, ice-scoured plains are characterized by extensive areas of standing water, including lakes, marshes, and muskeg (poorly drained areas grown over with vegetation that form in cold climates)

badlands

areas of weak, easily eroded clays or shales, rapid erosion from surface runoff can produce barren slopes and ridges dissected by a dense maze of steep gullies and ravines, areas of rugged, barren, and highly dissected terrain, barren region of soft rock material intensely eroded into ridges and ravines by numerous gullies and washes, have an extremely high drainage density

Deposition

as important as erosion in creating landform features in arid regions, and in many areas sedimentation by water does as much to level the land as erosion does

recurrence intervals

average length of time between events, such as floods, equal to or exceeding a given magnitude, the average number of years between past flow events that equaled or exceeded various discharges

Sea level

average position of the ocean shoreline, a complexly determined average position of the ocean shoreline and the vertical position (the reference, or datum) above and below which other elevations are measured

Sand

marks the boundary between fine-grained (small) clasts and coarse-grained (large) clasts

natural levees

bank of a stream channel (or margin of a mass wasting flow channel) raised by deposition from flood (or flow) deposits; artificial levees are sometimes built along stream banks for flood control, channel-bounding ridges created by aggradation

cobble beach

beach dominated by cobble-sized rocks deposited by waves along the shoreline, often found along the base of sea cliffs or lake cliffs

Wave refraction

bending of waves in map view as they approach the shore, aligning themselves with the bottom contours in the breaker zone, occurs when part of a wave encounters shallow water before other parts, when the wave breaks, its energy is focused on the headlands and spread out along the embayments, causes wave energy to be concentrated on headlands, eroding them back, whereas in embayments, deposition causes beaches to grow seaward

Calving

breaking off a mass of ice from the toe of a glacier at its junction with the ocean or a lake, refers to the loss of large chunks of ice from a glacier to an adjacent lake or ocean, where the chucks float away as icebergs

aggradation

building up of an area or landscape that results from more deposition than erosion over time, Net deposition of sediments

Jetties

built perpendicular to the coastline, but always in pairs, and act to keep sediment from blocking an inlet, such as a river mouth or a channel for boats

Turbulence

chaotic flow that mixes and churns the water, often with a significant upward component, greatly increases the rate of erosion as well as the load-carrying capacity of the stream, influenced by channel roughness and the gradient over which the stream is flowing, contribute to erosion by hydraulic action when they wedge under or pound away at rock slabs and loose fragments on the channel bed and sides, dislodging clasts that are then carried away in the current

corrosion

chemical erosion of rock matter by water; the removal of ions from rock-forming minerals in water, has a limited effect on many rocks but can be significant in certain rock types, such as limestone

Watersheds

clearly defined, well-integrated, natural regions of critical importance to life on Earth, and they make a logical spatial division for environmental management, provides much of the potable water resources for the world's population

coastlines of submergence

coastal area that has undergone sinking or subsidence relative to sea level, many features of the former shore lie underwater and the present shoreline crosses land areas that are not fully adjusted to coastal processes, created as global sea level rose in response to the retreat of the Pleistocene ice sheets, also occur where tectonic forces have lowered the level of the land, as in San Francisco Bay, classic examples of this type of submerging coastline are the Atlantic and Gulf coasts of the United States

estuary

coastal embayment where salt and fresh water mix, the load of a stream may be deposited for the long term in a delta or within an estuary, a biologically very productive embayment that forms at some river mouths where saltwater and freshwater meet, main source of coastal sediment

spits

coastal landform of wave- and current-deposited sediment attached to dry land at one end, coastal depositional landforms connected to the mainland at just one end, project out into the water like peninsulas of sediment, form where the mainland curves significantly inland while the trend of the longshore current remains at the original orientation, Sediments accumulate into a spit in the direction of the longshore current

Active-margin coasts

coastal region characterized by active volcanism and tectonism, best represented by coastal regions along the Pacific Ocean, most tectonic activity occurs around the ocean margins because of active subduction and transform plate boundaries along the Pacific Ring of Fire, usually characterized by high relief with narrow coastal plains, narrow continental shelves, earthquake activity, and volcanism, tend to be erosional, having less time within Earth history for the development of marine or continental depositional features, coast of Japan and the west coast of the United States are excellent examples of active-margin coasts

Passive-margin coasts

coastal region that is far removed from the volcanism and tectonism associated with lithospheric plate boundaries, tectonically quiescent, with little mountain-building or volcanic activity, Like the eastern seaboard of the United States, these coasts generally have low relief with broad coastal plains and wide continental shelves, typically dominated by depositional landforms and are well represented by the coastal regions of continents along the Atlantic Ocean

Pediments and inselbergs

common in desert areas that have been tectonically stable since a distant period of mountain formation, Development of exterior drainage helps transport sediment eroded from the mountains out of the basin

firn

compact granular snow formed by partial melting and refreezing due to overlying layers of snow, a density of about 0.5 gram per cubic centimeter, Over time, the small firn granules grow together into larger interlocked ice crystals through pressure, partial melting, and refreezing

The moon

completes its 360 orbit around Earth in a month, traveling about 12 per day in the same direction that Earth rotates daily around its axis, the moon rises 50 minutes later every day at any given spot on Earth, the tidal day is 24 hours and 50 minutes, and two successive high tides are ideally 12 hours and 25 minutes apart

kames

conical hill composed of sorted glaciofluvial deposits; presumed to have formed in contact with glacial ice when sediment accumulated in ice pits, crevasses, and among jumbles of detached ice blocks, are excellent sources for mining sand and gravel and they are especially common in New England

tides

consist of two very long wavelength waves caused by interactions between Earth and the moon and sun, There are two wave crests (high tides), each followed by a trough (low tide), so small on lakes that they have virtually no effect on coastal processes, even in large lakes, ocean at Earth's surface above the center of gravity is pulled toward the moon, making the first tidal bulge (high tide). At the same time, ocean water on the opposite side of Earth experiences the outward-flying, or centrifugal, force of inertia and forms the other tidal bulge. Troughs (low tides) occupy the sides of Earth midway between the two tidal bulges. As Earth rotates on its axis each day, these bulges and troughs sweep across Earth's surface, When the sun, moon, and Earth are aligned, as they are during new and full moons, the added influence of the sun on ocean waters causes higher than average high tides and lower than average low tides

coastal zone

consists of the general region of interaction between the land and the ocean or lake, ranges from the inland limit of coastal influence through the average position of the shoreline to the lowest elevation to which the shoreline fluctuates

bird's-foot delta

constructed in settings where the influence of the fluvial system far exceeds the ability of waves, currents, and tides of the standing water body to rework the deltaic sediment into coastal landforms or to transport it away, Numerous distributaries slightly above sea level extend far out into the receiving water body

three basic types of islands

continental, oceanic, and atolls

glacial system

controlled by two basic climatic conditions: frozen precipitation and freezing temperatures, to establish a glacier, there must be sufficient mass input (accumulation) to exceed the annual loss through ablation, Summer temperatures must not be high for too long, or all of the accumulation (primarily snowfall) from the previous winter will be lost through ablation (primarily melting), Surplus snowfall is essential for glacial formation because it allows the pressure from years of accumulated snow layers to transform older buried snow first into firn and then into glacial ice, When the ice reaches a depth of about 30 meters (100 ft), a pressure threshold is reached that enables the solid, glacial ice to flow

fringing reef

coral reef attached to the coast, tend to be wider where there is more wave action that brings a continuous supply of well-aerated water and additional nutrients for increased coral growth, usually absent near river mouths because the coral cannot grow where the waters are laden with sediment or where river water lowers the salinity of the marine environment

barrier reef

coral reef parallel to the coast and separated from it by a lagoon, lies offshore, occur in association with slowly subsiding oceanic islands, growing at a pace that keeps them above sea level, Other barrier reefs, including Australia's Great Barrier Reef, the Florida Keys, and the Bahamas, were formed on continental shelves and grew upward as sea level rose after the Pleistocene ice age waned. At more than 2000 kilometers (1250 mi) long, the world's largest organic structure is the Great Barrier Reef of Australia

Antarctic ice sheet

covers some 13 million square kilometers (5 million sq mi), almost 7.5 times the area of the Greenland ice sheet, only a small amount of land is exposed in Antarctica, and the weight of the 4.5-kilometer (nearly 3-mi) thick ice in some interior areas has depressed the land well below sea level

Greenland ice sheet

covers the world's largest island with a glacier that is more than 3 kilometers (2 mi) thick at its center, The only land exposed in Greenland is a narrow, mountainous coastal zone

Barchans

crescent-shaped sand dune with arms (horns) pointing downwind, The main body of the crescent lies on the upwind side of the dune, The slip face is oriented perpendicular to the barchan's arms, form in areas of minimal sand supply where winds are strong enough to move sand downwind in a single prevailing direction, may be most common in smaller desert basins surrounded by highlands where they tend to form near the downslope, sandy edge (toe) of alluvial fans, and adjacent to small playas. Although they may form as isolated dunes, barchans often appear in small groups, called barchan fields

parabolic dune

crescent-shaped sand dune with arms pointing upwind, the orientation of the crescent in this case is reversed from that of a barchan, the arms of the crescent are stabilized by vegetation, are long, and point upwind, trailing behind the unvegetated main body and crest of the dune rather than extending downwind from it, The main body of a parabolic dune points downwind, and the slip face along its downwind edge has a convex shape when viewed from above, commonly occur just inland of beaches and along the margin of active dune areas in deserts

delta

depositional landform constructed where a stream flows into a standing body of water (a lake or the ocean), because the map view shape of some resembles the Greek letter delta (∆), will be constructed, form at the interface between fluvial systems and coastal environments of lakes or the ocean, and therefore originate in part from fluvial and in part from coastal processes, have a subaqueous (underwater) coastal component, called the prodelta, and a fluvial part, the delta plain, that exists at, to slightly above, the lake level or sea level, form only at those river mouths where the fluvial sediment supply is high, the underwater topography does not drop too sharply, and waves, currents, and tides cannot transport away all the sediments delivered by the river, Continued deposition and delta formation extend the delta plain and create new land beyond the original shoreline

ephemeral flow

describes streams that conduct flow only occasionally, during to shortly after precipitation events or due to ice or snowmelt

intermittent flow

describes streams that conduct flow seasonally, lasts for a couple of months in response to an annual rainy season or spring snowmelt

bolsons

desert basin, surrounded by mountains, with no drainage outlet, Desert basins of interior drainage surrounded by mountains, topographically closed basins, most formed by faulting that created basins between uplifted mountains

desert pavement

desert surface mosaic of close-fitting stones that overlies a deposit of mostly fine-grained sediment, Deflation one of several possible factors contributing to this, a close-fitting mosaic of gravel-sized stones that overlies a deposit of mostly finer-grained sediments, common in many arid regions, particularly in parts of the Sahara, interior Australia, the Gobi in central Asia, and the American Southwest, Sheet wash (unchannelized running water) also contributes to the formation of some desert pavements by selectively eroding only the fine-grained clasts from an area of mixed grain sizes, helps to stabilize desert surfaces by protecting the fine-grained material below the pavement from erosion, is fragile, and easily disturbed by vehicles

fetch

distance over open water that winds blow without interruption, the expanse of open water across which the wind can blow without interruption

potholes

distinctive round depressions in the rock of a bedrock streambed caused by stream abrasion, generally originate in specific ideal locations, such as below swirling rapids, at the base of waterfalls, or at points of structural weakness, which include joint intersections in the bedrock on the channel bed, range in diameter and depth from a few centimeters to many meters

trellis

drainage pattern consisting of long, parallel streams with short tributaries entering at right angles, indicates folded terrain where short streams flow down the sides of resistant rock ridges into a larger stream that occupies the adjacent valley that consists of erodible rock, as in the Ridge and Valley region of the Appalachians, indicates parallel valleys of weak rock between ridges of resistant rock

deranged

drainage pattern in which streams flow on low-gradient terrain left by the receding glaciers, wandering between marshes and small lakes in a chaotic pattern

dendritic

drainage pattern that resembles a branching tree with tributaries joining larger streams at acute angles, common and develop where the rocks have a roughly equal resistance to weathering and erosion and are not intensely jointed

centripetal

drainage pattern with the streams converging on a central lowland, as in an arid region basin of interior drainage

Rectangular

drainage patterns occur where streams follow sets of intersecting fractures to produce a blocky network of straight channels with right-angle bends

all-terrain vehicles (ATVs)

driving motorized vehicles of any kind over the desert landscape off established roadways has tremendous negative impacts on desert flora and fauna, the habitat of those organisms, the stability of landforms and landforming processes, and the aesthetic beauty of the natural desert environment, One major problem is that ORVs compact the desert surface sediments and soil. Compaction causes a decrease in permeability, which greatly restricts the ability of water to infiltrate into the subsurface. More surface runoff translates to greater erosion of the already thin desert soils. In addition, even long after ORV use ceases in a disturbed area, soil compaction makes it very difficult for desert plants, animals, and insects to become reestablished there.

Fjords

drowned glacial valleys, A coastline with fjords is highly irregular, with deep, steep-sided embayments penetrating far inland in U-shaped valleys originally deepened by glaciers. Tributary streams cascade down fjord sidewalls, which may be a few thousand meters high. Fjord coastlines are found in Norway (where the term originated), Chile, New Zealand, Greenland, and Alaska. Canada, however, has more fjords than any other nation. In many fjords, the glaciers have retreated far inland, but in others, especially in Greenland and Alaska, glaciers still reach the fjords calving icebergs into their cold ocean water

base level

elevation below which a stream cannot flow; most humid region streams flow to sea level (ultimate base level)

shoreline

exact contact between the edge of a standing body of water and dry land, The position of this boundary fluctuates with incoming waves, with storms, and, in the case of the ocean, with the tides. Over the long term, the position of the shoreline is also affected by tectonic movements and by the amount of water held in the ocean or lake basin, of a standing body of water is the exact and constantly changing contact between the ocean or lake surface and dry land

Antecedent streams

exist before the establishment of the mountains that they flow across, The Columbia River Gorge through the Cascade Range in Washington and Oregon and many of the great canyons in the Rocky Mountain region, such as Royal Gorge and the Black Canyon of the Gunnison, both in Colorado, probably originated as antecedent streams, establish their flow paths before existence of the structure that they now cut across

glacier advance

expansion of the toe or terminus of a glacier to a lower elevation or lower latitude due to an increase in size, net accumulation

nearshore zone

extends from the seaward or lakeward edge of breakers to the landward limit reached by the broken wave water, contains the breaker zone where waves break, the surf zone through which a bore of broken wave water moves, and, most landward, the swash zone over which a thin sheet of water rushes up to the inland limit of water and then back toward the surf zone

alluvial plains

extensive floodplain of very low relief, during floods becomes inundated with sediment-laden water that contributes vertical accretion deposits to the large natural levees and to the already thick alluvial valley fill of the floodplain in general

outwash plains

extensive, relatively smooth plain covered with sorted deposits carried forward by the meltwater from a continental glacier, composed of meltwater deposits, These extensive areas of relatively low relief consist of glaciofluvial deposits that are sorted as they are transported by meltwater from the ice sheets. Outwash plains, which may cover hundreds of square kilometers, are analogous to the valley trains of alpine glaciers

Snow

falls as hexagonal ice crystals that form flakes of intricate beauty and variety, Snowflakes have a low density, Once snow accumulates on the land it becomes transformed by compaction, along with melting and refreezing at pressure points, into a mass of smaller, rounded grains, Density increases as the air space around this more granular snow continues to decrease by compaction and melting and refreezing

debris flow fans

fan-shaped depositional landform, particularly common in arid regions, created where debris flows emerge onto a plain from a mountain canyon, areas where the uplands generate debris flows rather than stream flows, mixed debris flow and alluvial fans are constructed instead of purely alluvial fans, tend to be steeper than alluvial fans and do not display the same degree of downslope sorting of grain sizes shown by the fluvial counterpart

alluvial fan

fan-shaped depositional landform, particularly common in arid regions, occurring where a stream emerges from a mountain canyon and deposits sediment on a plain, deposition takes place radially away from a pivot point, or fan apex. important characteristic is sorting of sediment that occurs on its surface, Coarse sediments, like boulders and cobbles, are deposited near the fan apex where the stream first undergoes a decrease in competence and capacity as it emerges from the confinement of the canyon. In part because of the large size of the clasts deposited there, the slope of an alluvial fan is steepest at its apex and gradually diminishes, along with grain size, with increasing distance downstream from the canyon mouth, particularly common where ephemeral or intermittent streams laden with coarse sediment flow out of a mountainous region onto desert plains or into arid interior basins, alluvial fans are a major landform in landscapes consisting of fault-block mountains and basins

mesas

flat-topped, steep-sided erosional remnant reminiscent of a table, broader than tall, and common in arid regions with flat-lying sedimentary rocks, Weathering and erosion will eventually reduce the extent of a caprock until only flat-topped, steep-sided mesas remain, has a smaller surface area than a plateau and is roughly as broad across as it is tall, relatively common landscape features in the Colorado Plateau region

Secondary coastlines

formed mainly by coastal geomorphic agents, especially waves, and by aquatic organisms, Sea cliffs, arches, sea stacks, and sea caves generally dominate erosional secondary coasts, like that of Oregon, Depositional secondary coasts typically display barrier beaches and spits, such as the coastline of North Carolina. An example of coasts built by aquatic organisms is the coral reef. The Florida Keys were constructed by coral growth. Mangrove trees and salt-marsh grasses also trap sediment to build new land areas in shallow coastal waters.

stream terraces

former floor of a stream valley now abandoned and perched above the present valley floor and stream channel, Variations in base level, tectonic movements, and changes in discharge and load can each cause downcutting in stream valleys, so the valley is slightly deepened, and remnants of the older, higher valley floor are preserved in stair-stepped banks along the walls of the valley, Multiple terraces are a consequence of successive periods of downcutting and deposition, provide a great deal of evidence about the geomorphic history of the river and its surrounding region

horn

forms where several glaciers cut headward into a mountain peak, Matterhorn in the Swiss Alps, Where three or more cirques surround a mountain summit, headward erosion eventually carves the high ground between them into a pyramid-shaped peak

Alluvium

general term for clastic particles deposited by a stream, the general term for fluvial deposits, regardless of the type or size of material, recognized by the characteristic sorting and rounding of sediments that streams perform

lateral accretion deposits

generally channel bar deposits that get left behind as a stream gradually shifts its position in a sideways fashion (laterally) across the floodplain

Sea level Rise

generally rose over the 20th century, and it is expected to rise at a faster rate in the 21st century as climate change takes its toll on the Greenland and Antarctic ice sheets and Earth's ice caps, combined with thermal expansion of the ocean. Studies suggest a sea level rise of approximately 32 centimeters (12.6 in.) by 2050. In addition to the huge expense of trying to protect or move structures that people have built close to sea level, this rise in ultimate base level will affect the behavior of streams that reach the ocean, and new spatial configurations of the shoreline will cause new patterns of erosion, transportation, and deposition along many coasts.

pediment

gently sloping surface of eroded bedrock, thinly covered with fluvial sediments, found at the base of an arid-region mountain, As the bedrock slope of the mountain front migrates slowly away from the basin floor or plain, it leaves behind a gently sloping surface of the eroded bedrock, most pediments are erosional surfaces created or partially created by the action of running water. In some areas, weathering, perhaps when the climate was wetter in the past, also appears to have played a strong role in the development of pediments

Red River in North Dakota, Minnesota, and Manitoba

glacial plains where they consist of glaciolacustrine deposits, one of the flattest landscapes in the world, is of great agricultural significance, created by deposition in a vast Pleistocene lake held between the front of the receding continental ice sheet on the north and moraine dams and higher topography to the south, The Red River flows northward eventually into the last remnant of Lake Agassiz, Lake Winnipeg, which occupies the deepest part of an ice-scoured and sediment-filled lowland

United Nations Educational, Scientific, and Cultural Organization (UNESCO)

has since helped member nations in the region develop a tsunami warning system, tragic event in Indonesia in 2004 reinforced the importance of tsunami early-warning systems

Dunes

help protect adjacent inland areas from storm waves, particularly important to communities along the low-lying Gulf and Atlantic coasts of the United States, where hurricanes and midlatitude cyclones batter the coastlines. In the Netherlands, coastal dunes are extremely important because the land behind them is below sea level; thus a breach through the dunes could mean disastrous inundation. Desert and coastal dune regions both serve as critical wildlife habitats

dams

hold back potentially devastating floodwaters and store the discharge of wet periods to make the water available during dry seasons or drought years, also used to generate hydroelectric power

Continental islands

island that is geologically part of a continent and usually located on the continental shelf, Most large continental islands became separated from the continent because of global sea-level change or regional tectonic activity, A few large continental islands, such as New Zealand and Madagascar, are isolated continental fragments that separated from continents millions of years ago. The world's largest islands—Greenland, New Guinea, Borneo, and Great Britain—are continental. Smaller continental islands include the barrier islands off the Atlantic and Gulf coasts of the United States, New York's Long Island, California's Channel Islands, and Vancouver Island off the west coast of Canada

wind

less effective than mass movement, running water, moving ice, or waves in accomplishing geomorphic work, The three principal conditions necessary for wind to be effective as a geomorphic agent are a sparse vegetative cover; the presence of dry, loose materials at the surface; and a wind velocity that is high enough to pick up and move those surface materials, the wind detaches and transports rock fragments in ways comparable to flowing water, but it does so with less overall effectiveness because air has a much lower density than water, compared to streams, the wind has fewer lateral or vertical limitations on movement, A principal similarity between the geomorphic properties of wind and running water is that flow velocity controls their competence—that is, the size of particles each can pick up and carry

striations

linear scratches, grooves, and gouges—where sharp-edged rocks scrape across bedrock , gouge, groove, or scratch carved in bedrock by abrading rock particles imbedded in a glacier, caused by Glacial abrasion, indicate direction of ice flow long after the ice has disappeared from the landscape

surface runoff

liquid water flowing over Earth's land surface, also known as overland flow, can originate as ice and snow melt or as outflow of subsurface water, such as at springs, but most runoff originates in direct response to precipitation arriving as rain, generated when the amount of precipitation exceeds the ability of the ground to soak up the moisture, depends on the intensity and duration of a rainstorm, surface features that affect infiltration, and the amount of evapotranspiration

Beach drifting

littoral drifting in which waves breaking at an angle to the shoreline move sediment along the beach in a zigzag fashion in the swash zone, caused by incomplete wave refraction, Over time, beach drifting transports tons of sediment along the shore

blowout

local, wind-eroded surface depression in an area dominated by wind-deposited sand, If the vegetation cover on a stabilized dune is breached, perhaps from damage by range animals or off-road vehicles, the wind can then remove some of the sand, creating a local blowout

Plunge pools

located at the base of waterfalls and in rapids, reveal the power of turbulence-enhanced hydraulic action where it is directed toward a localized point

Pacific Tsunami Warning Center

locates earthquake epicenters and estimates arrival times for potential tsunamis in the Pacific region

Wind erosion

mainly confined to picking up fine, dust-sized (clay and silt) particles from desert regions and to dislodging loose rock fragments of sand-sized materials

Stabilized dunes

maintain their shape and position over time, Vegetation can stabilize an active sand dune if plants gain a foothold and send roots down to moisture deep within the dune, One extensive area of stabilized dunes in North America is the Sand Hills of Nebraska

Dynamic equilibrium

maintained by adjustments among channel slope, shape, and roughness; amount of load eroded, carried, or deposited; and the velocity and discharge of stream flow

equilibrium line

marks the elevation on the glacier where annual accumulation equals annual ablation, internal plastic flow transports ice from the accumulation zone to the ablation zone, marks the boundary between the zones of accumulation and ablation on an alpine glacier, At elevations above the equilibrium line, fresh snow and ice added to the surface of the glacier during the cooler accumulation season does not completely disappear during the warmer ablation season. Below the equilibrium line, the winter's input of fresh ice and snow ablates away in the summer, the highest elevation achieved by the snow line on the glacier during the year

stream load

material being transported by a stream at a given instant; includes bed load, suspended load, and dissolved load, In order from smallest to largest, the size of sediment that a stream might transport includes clay, silt, sand, granules, pebbles, cobbles, and boulders

straight channels

may exist for short distances under natural circumstances, especially along fault zones, joints, or steep gradients, most channels with parallel linear banks are artificial features that were totally or partially constructed by people

basal sliding

meltwater at the base of the glacier reduces friction between the ice and ground by means of lubrication and hydrostatic pressure, When frictional resistance becomes too small to resist the downslope pull of gravity on the ice mass, the affected part of the glacier jerks forward, common in many temperate glaciers—those with temperatures at and near the melting point, This type of motion is most common in midlatitude glaciers on steep slopes, particularly during summer when much of the glacier is near the melting point and meltwater is available

solution

minerals that are dissolved in the water and are thus carried in the transportation process

Flowing water

more influential in shaping the surface form of our planet than any other exogenic geomorphic process, primarily because of the sheer number of streams on Earth

net ablation

more removal than addition of frozen water for the year, glacier shrinks in size causing the toe to retreat upvalley

sand dunes

mound or hill of sand-sized sediment deposited and shaped by the wind, Dune topography is highly variable, The specific type of dune that forms depends on the amount of sand available, the strength and direction of sand-transporting winds, and the amount of vegetative cover, Dunes grow larger until equilibrium is reached between dune size and the ability of the wind to deliver sand grains to the dune.

Wind as a Geomorphic Agent

moves sediment in the transportation processes of suspension, saltation, and surface creep

Lakes

natural standing bodies of inland water, form wherever the water supply is adequate to accumulate in topographic depressions on the land surface, Many of the world's lake basins, such as those of the North American Great Lakes, are products of glaciation, but rivers, tectonic activity, and volcanism also produce lake basins, Most lakes are temporary features on Earth's surface. Few have been in existence for more than 10,000 years, and the majority are very recent in terms of Earth history, Sedimentation, biological activity, or downcutting of an outlet by a stream eventually lead to the destruction of most lakes, affect the nearby climates, particularly by reducing daily and seasonal temperature ranges and by increasing humidity

First-order streams

no perennial tributaries, the smallest perennial channels in the drainage basin, most lie high up in the drainage basin near the drainage divide, the source area of the stream system

Stream ordering

numerical index expressing the position of a stream channel within the hierarchy of a stream system, the technique used to describe quantitatively the position of a stream and its drainage basin in the nested hierarchy of tributaries, as stream order increases, basin area, channel length, channel size, and amount of flow also increase

glacier toe

occupies its farthest downvalley position near the end of winter and its farthest upvalley position at the end of the ablation season, near the end of summer, The downslope end of a glacier is called its terminus, or the glacier toe, Braided meltwater streams laden with sediment commonly issue from the glacier terminus

Coastlines of emergence

occur where the water level has fallen or the land has risen in the coastal zone, land that was once below sea level has emerged above the water, Evidence for emergence includes marine terraces and relict sea cliffs, sea stacks, and beaches found above the reach of present wave action, Many coastlines of emergence would have existed during the glacial phases of the Pleistocene Epoch when sea level was about 120 meters (400 ft) lower than it is today, Features of emergence are common along active-margin coasts such as those of California, Oregon, and Washington, where tectonic uplift has raised coastal landforms as much as 365 meters (1200 ft) above sea level

channel incision

occurs only when there is net erosion compared with deposition

Greater infiltration

occurs under conditions of permeable surface materials, deeply weathered sediments and soils, gentle slopes, dry initial soil conditions, and a dense cover of vegetation

The Great Lakes

of the eastern United States and Canada make up the world's largest lake system, Lakes Superior, Michigan, Huron, Erie, and Ontario occupy former river valleys that were vastly enlarged and deepened by glacial erosion. All the lake basins except that of Lake Erie have been gouged out to depths below sea level and have irregular bedrock floors lying beneath thick blankets of glacial till. The history of the Great Lakes is exceedingly complex, resulting from the back-and-forth movement of the ice front that produced many changes of lake levels and overflow in varying directions at different times, formed as the ice sheet receded at the close of the Pleistocene Epoch

grinders

one or more round stones at the bottom of a pothole, Swirling whirlpool movements of the stream water cause such stones to grind the bedrock and enlarge the pothole by abrasion, whereas finer sediments are carried away in the current

swell

orderly lake or ocean waves of rounded form that have traveled beyond the storm zone of wave generation, It is swell that arrives at coastlines even in the absence of coastal winds

Salt weathering

particularly significant in preparing rocks for removal through chemical and physical weathering along the marine coast and coasts of salt lakes

periglacial

pertaining to cold-region landscapes that are impacted by intense frost action but not covered by year-round snow or ice, environments lacking year-round snow or ice cover, undergo intense frost action and are frequently regions of permafrost (permanently frozen ground), Large areas of periglacial terrain exist today in Alaska, Canada, Russia, and some areas of high elevation including in mountain and plateau regions of China, The intense frost action of periglacial landscapes includes freezing of soil moisture and produces angular, shattered rocks. Frost action also causes heaving, thrusting, and size-sorting of stones in the soil that lead to the formation of fascinating repeating designs in patterned ground features

stream hydrograph

plot showing changes in the amount of stream flow over time, the record of discharge changes in a stream over time, often used to indicate how high and fast the water level rises in response to a precipitation event

energy in a wave

potential energy represented by the wave height, As waves travel they lose a little height, and thus energy, as a result of friction and from the spreading of the wave crest because of the curvature of Earth, but overall they are very efficient means for transporting energy, There is little if any net forward motion of water molecules during the passage of the wave

permafrost

result in considerable solifluction (slowly flowing soil) on slopes when the upper, active layer of the permanently frozen ground thaws in the summer and becomes saturated. Permafrost areas are also prone to the formation of fissures that accumulate ice, leading to the formation of large ice wedges in the ground, Unless proper construction techniques are used, erecting buildings, roads, pipelines, and other structures on permafrost disrupts the natural thermal environment, often leading to permafrost melting. Saturated ground cannot support the weight of structures resting on top of them. As the ground deforms and slowly flows, the structures are destroyed, The latter is generally accomplished by building above the surface so that air can circulate to the permafrost

Geomorphologists

routinely measure stream channel, drainage basin, and flow properties and analyze them using statistical methods and the principles of fluid mechanics so that they can describe, compare, monitor, predict, and learn more about streams and the geomorphic work that they perform

till

sediment deposited directly by glacial ice

drift

sediment deposited in association with glacial ice or its meltwater, general term for all deposits of glacial ice or its meltwater, and therefore including till and glaciofluvial deposits

littoral drifting

sediment transportation in the coastal zone, general term for sediment transport parallel to shore in the nearshore zone due to incomplete wave refraction

Continental Divide

separates North America into a western region where most runoff flows to the Pacific Ocean and an eastern region where runoff flows to the Atlantic Ocean, generally follows the crest line of high ridges in the Rocky Mountains

Coral reefs

shallow, wave-resistant structures made by the accumulation of remains of tiny sea animals that secrete a skeleton of calcium carbonate, need special conditions to grow—clear and well-aerated water, water temperatures above 20*C, plenty of sunlight, and normal marine salinity, These conditions are found in the shallow waters of tropical regions, including Hawaii, the West Indies, Indonesia, the Red Sea, and the coast of Queensland in Australia. Today coastal water pollution, dredging, souvenir coral collecting, and climate change threaten the survival of many coral reefs

Ice sheets and ice caps (continental glaciers)

shaped somewhat like a convex lens in cross-section, thicker in the center and thinning toward the edges, flow radially outward in all directions from where the pressure is greatest, in the thick, central zone of accumulation, to the surrounding zone of ablation

meandering channels

stream channel with broadly sinuous banks that curve back and forth in sweeping bends, wander from side to side across their low-gradient floodplains, widening the valley by lateral erosion on the outside of meander bends and leaving behind lateral accretion (bar) deposits on the inside of meander bends, these streams and their floodplains have a higher proportion of fine-grained sediment and thus greater bank cohesion than the typical braided stream

alluvium

stream sediments, Many desert areas have wide expanses of alluvium deposited either in closed basins or at the base of mountains by streams as they lose water in the arid environment

exotic streams

stream that originates in a humid region and has sufficient water volume to flow across a desert region, like the Nile River in Sudan and Egypt, provide some desert areas with exterior drainage

exterior drainage

streams and stream systems that flow to the ocean, Drainage basins with channel systems that convey their water to the ocean

interior drainage

streams and stream systems that flow within a closed basin and thus do not reach the ocean, common in arid regions

perennial flow

streams that flow all year and are typical of humid environments

crevasses

stress crack commonly found along the margins and at the toe of a glacier, common wherever a glacier becomes stretched, experiencing tensional stress, particularly where it moves over a break in slope

tombolo

strip of wave- and current-deposited sediment connecting the mainland to an island, a strip of sediment connecting the mainland to an island

longshore bar

submerged feature of wave- and current-deposited sediment lying close to and parallel with the shore, deposit of sand-sized sediment eroded from the beach in winter, with the sediment returning to the beach in summer

Decreased infiltration

surface materials of low permeability and limited weathering, thin soils, steep slopes, preexisting soil moisture, and sparse vegetation

third-order stream

takes the intersection of two second-order channels, The ordering system continues in this way, requiring two streams of a given order to combine to create a stream of the next higher order

Desert Soil

tend to be thin, rocky, and discontinuous, surface conditions of very limited interception and low permeability, much of the rain that falls in the desert quickly becomes surface runoff available to perform fluvial geomorphic work

capacity

the amount of load a stream can transport

infiltration capacity

the amount of water that can enter the voids and pore spaces in the soil and surface sediments at a given location

Bonneville Salt Flats

the bed of an extinct Pleistocene lake, called Lake Bonneville, of which Great Salt Lake is a small remnant

Interception

the delay in arriving at the ground surface experienced by precipitation that strikes vegetation, allows greater infiltration by slowing down the rate of delivery of precipitation to the ground

Streams

the dominant geomorphic agent on Earth's surface, the general term for natural, channelized flow, pertains to water flowing in a channel of any size, have no influence over the amount of water entering the channel system, nor can they change the type of rocks over which they flow, have some control over their channel size, shape, and gradient

Stream gradient

the drop in stream elevation over a given horizontal distance along the stream course, and is usually expressed in meters per kilometer (m/km) or feet per mile (ft/mi), water flows faster down channels with steeper slopes and slows down over gentler slopes, Steeper channels typically occupy locations that are farther upstream and higher in the drainage basin as well as places where the stream flows over rock types that are more resistant to erosion. Gentler stream gradients tend to occur closer to the mouth of a stream and where the stream crosses easily eroded rock types

kinetic energy

the energy of motion, when a stream has more kinetic energy, it can pick up and move more clasts (rock particles) and heavier clasts than when it has less energy, the amount of energy a stream has depends on its mass (m), but especially on its velocity of flow (v), because kinetic energy varies with velocity squared, stream velocity is a critical factor in determining the amount of geomorphic work that can be accomplished by a stream, Besides discharge variations, another major way to alter stream velocity, and thereby stream energy, is through a change in the slope, or gradient, of the stream

U.S. Army Corps of Engineers

the federal agency responsible for the development of inland and coastal waterways, chose Miami Beach to experiment with the beach building method of shoreline protection

glacial outwash

the fluvial deposits derived from glacial meltwater streams, sediment that is deposited beyond the terminal moraine of the alpine glacier, with larger rocks deposited first, followed downstream by progressively finer particles

drainage patterns

the form of the arrangement of channels in a stream system in map view, 2 primary factors that influence drainage patterns are bedrock structure and surface topography

ice sheets

the largest type of glacier, bury Greenland and Antarctica to a maximum depth of at least 3 kilometers (2 mi), In contrast to alpine glaciers, ice sheets and ice caps more or less drown the underlying topography in ice, rather than being confined or directed by the topography, Direction of movement within ice sheets and ice caps is from thicker to thinner ice, which is radially outward in all directions from a central source area of maximum ice thickness

regional base level

the low point of flow for a stream with interior drainage

Floodplains

the low-gradient area adjacent to many stream channels that is subject to flooding and primarily composed of alluvium, constitute the often extensive, low-gradient land areas composed of alluvium that lie adjacent to many stream channels

regional base level

the lowest level to which a stream system in a basin of interior drainage can flow, When sedimentation raises the elevation of the desert basin floor located at the stream's terminus, the stream's base level rises, causing a decrease in the stream's slope, velocity, and energy, If tectonic activity lowers the basin floor, the regional base level falls, which could rejuvenate the desert stream

stream capacity

the maximum amount of load that a stream can carry; varies with the stream's velocity. the total amount of load being moved by the stream, depend on available stream energy and thus on the flow velocity

snow line

the minimum elevation at which snow cover lies on a landscape, changes position multiple times throughout the year and even daily, such as in response to individual snowstorms

channels of ephemeral streams

the most common desert landforms created by surface runoff and erosion

fan apex

the most upstream point on an alluvial fan; where the fan-forming stream emerges from the mountain canyon

Ablation

the opposite of accumulation, representing any removal of frozen water mass from a glacier, most ablation is accomplished in summer through melting, glaciers also lose mass by direct change from ice to water vapor (solid to gas) and by other processes that may be at work

drainage divide

the outer boundary of a drainage basin, the outside perimeter of a drainage basin and thus also the boundary between it and adjacent basins, follows the crest of the interfluve between two adjacent drainage basins

Glacial plucking

the process by which moving ice freezes onto loosened rocks and sediments, incorporating them into the flow, erosion process by which a glacier pulls rocks and sediment from the ground along its bed and into the flowing ice, Weathering, particularly the freezing of water in bedrock joints and fractures, breaks rock fragments loose, encouraging plucking

infiltration

the process of water soaking into the ground

attrition

the reduction of size in sediment as it is transported downstream, explains why gravels found in streambeds are smooth and rounded and why the load carried in the lower reaches of most large rivers is composed primarily of fine-grained sediments and dissolved minerals

drainage basin

the region that provides runoff to a stream, open systems that involve inputs and outputs of water, sediment, and energy, The order of a drainage basin derives from the largest stream order found within it

Fluvial erosion

the removal of rock material by flowing water, process consists of the chemical removal of ions from rocks and the physical removal of rock fragments (clasts)

Corrosion

the removal of the ions that have been separated from rock-forming minerals by solution and other chemical weathering processes

vertical accretion deposits

the sediment that settles out of slowing and standing floodwater

hydraulic action

the sheer physical force of the water alone pounds against and removes coastal rock material, sometimes compressing air or water into cracks to help in the process

lateral migration

the sideways shift in the position of a stream channel over time, Erosion on the outside and deposition on the inside of stream meander bends result in this sideways displacement

neap tide

the smaller than average tidal range that occurs during the first- and third-quarter moon, occurs every 2 weeks

cut bank

the steep slope found on the outside of a bend in a meandering stream channel, where the channel is deep and centrifugal force accelerates stream velocity

slip face

the steep, downwind side of a sand dune, lies at the angle of repose for dry, loose sand

Middle Stream Course

the stream flows over a moderate gradient and on a moderately smooth channel bed, the stream valley includes a floodplain, but remaining ridges beyond the floodplain still form definite valley walls, the stream lies closer to its base level, flows over a gentler gradient, and thus directs less energy toward vertical erosion than in its upper course, Because of lateral erosion, the middle course of the stream develops a definite meandering channel pattern with its sinuous bends that wander over time across the valley floor

longitudinal profile

the stream gradient from source to mouth

Upper Stream Course

the stream primarily flows in contact with bedrock, Over the steep gradient high above its base level, the stream works to erode vertically downward by hydraulic action and abrasion, Erosion in the upper course creates a steep-sided valley, gorge, or ravine as the stream channel in the bottom of the valley cuts deeply into the land, Little if any floodplain is present, and the valley walls typically slope directly to the edge of the stream channel. Steep valley sides encourage mass movement of rock material directly into the flowing stream. Valleys of this type, dominated by the downcutting activity of the stream, are often called V-shaped valleys because with their steep slopes they attain the form of the letter V, The effects of differential erosion can be significant in the upper course if the stream cuts through rock layers of varying resistance

drainage density

the summed length of all stream channels per unit area in a drainage basin, the total length (L) of all channels in the drainage basin, divided by the area of the drainage basin, indicates how dissected the landscape is by channels, it reflects both the tendency of the drainage basin to generate surface runoff and the erodibility of the surface materials, Regions with high drainage densities have limited infiltration, considerable runoff, and at least moderately erodible surface materials

saltation

the transportation by running water or wind of particles too large to be carried in suspension; the particles are bounced along on the surface or streambed by repeated lifting and deposition

standing bodies of water

the water in each (large lakes and oceans) occupies a basin and has an approximately uniform still-water level around the basin

swash

thin sheet of broken wave water that rushes up the beach face in the swash zone, thin sheet of water rushing toward the land

sheet wash

thin sheet of unchannelized water flowing over land, also called unconcentrated flow

backwash

thin sheet of water from a wave that rushes back down the beach face in the swash zone, the return flow

wave period

time it takes for one wavelength to pass a given point

longshore drifting

transport of sediment parallel to shore by the longshore current., when incompletely refracted waves break

traction

transportation process in moving water that drags, rolls, or slides heavy particles along in continuous contact with the bed, particles that are too large and heavy to move by saltation, but still small enough to move, slide and roll along the channel bottom in the transportation process

suspension

transportation process that moves small solids, often considerable distances, while buoyed up by turbulence in the moving air or water, movement of the finest solid particles

Waves

traveling, repeating forms that consist of alternating highs and lows, called wave crests and wave troughs, respectively, Waves that have traveled across the surface of a water body are the principal geomorphic agent responsible for coastal landforms, waves erode, transport, and deposit Earth materials, continually reworking the narrow strip of coastal land with which they come in contact

Desert streams

typically have ephemeral flow, containing water only for brief intervals and remaining dry the rest of the time, streams with ephemeral flow do not receive seepage from groundwater to sustain them between episodes of surface runoff, Ephemeral streams instead lose water to the groundwater system through infiltration into the channel bed, many desert streams undergo a downstream decrease, rather than increase, in discharge, A discharge decrease occurs for two major reasons: infiltration into the gravelly streambed continues downstream, removing more and more water from the channel, and evaporation losses increase downstream because of warmer temperatures at lower elevations

superimposed stream

uncovers and excavates ancient structures that were buried beneath the surface, as the stream erodes the landscape downward, it cuts across and through the ancient structures, developed its course on the younger strata independent of the characteristics of the buried structure

Glaciofluvial

used to specify the better sorted and stratified fluvial deposits related to glacial meltwater

internal plastic deformation

virtually all moving glaciers experience this type of flow, Glaciers move in this plastic way when the weight of overlying ice, firn, and snow causes ice crystals at depth to arrange themselves in parallel layers that glide over each other, much like spreading a deck of cards, happens when a threshold pressure (weight per unit area) from the overlying mass is exceeded, The threshold pressure is achieved at an ice thickness of about 30 meters (100 ft), and the zone experiencing plastic flow extends from that ice depth to the base of the glacier, The speed at which the ice flows increases as pressure from overlying material grows and with steeper slopes, Pressure is greater under thicker accumulations of ice and on the upflow side of obstacles at the base of a glacier. Internal plastic deformation causes continental glaciers to flow radially outward from central areas of thicker ice (higher pressure) to marginal areas of thinner ice (lower pressure)

meandering river channel

water flowing in a channel has a tendency to flow downstream in a helical, or corkscrew, fashion, which moves water against one side of the channel and then to the opposite side. The up-and-down motion of the water contributes to the processes of erosion, transportation, and deposition

wind waves

wave on a water body created when air currents push the water surface along, Most of the waves that have an impact on the coastal zone, Where wind blows across the water, frictional drag and pressure differences cause irregularities in the water surface. The wind then pushes on water slopes that face into the wind, transferring energy to the water and building the slopes into larger waves

abrasion platform

wave-cut bench of rock just below the water level; indicates the landward extent of coastal cliff erosion, sometimes visible at lower water levels, such as at low tide, caused by landward recession of a sea cliff, record the amount of cliff recession

glacial surges

when a glacier's velocity increases by many times its normal rate, causing the glacier to flow hundreds or even thousands of meters per year, meltwater reducing friction at the base of the ice is probably involved

rejuvenated

when a stream uses its renewed energy to incise its channel, Waterfalls and rapids might develop as rejuvenated channels are deepened by erosion

base flow

when slow-moving groundwater seeps directly into the stream through the channel bottom and sides at and below the level of the water surface, found in perennial streams, a humid climate is needed to generate sufficient base flow to maintain a perennial stream between rainstorms

zone of ablation

where annual ablation exceeds annual accumulation in the warmer downslope portion of an alpine glacier, the lower elevation part of a glacier; where more frozen water is removed than added during the year, Winter is the dominant accumulation season and summer is the dominant ablation season

subbasins

where small tributary basins are nested within a succession of larger and larger trunk stream drainage basins

Three factors that determine the height of wind waves as they form in deep, open bodies of water are:

wind velocity, duration of the wind, and the area over which the wind blows, known as the fetch, An increase in any of these three factors produces waves of greater height and greater energy

loess

wind-deposited silt; usually transported in dust storms and derived from arid or glaciated regions, particles settle out to form a tan, yellowish, or grayish blanket of loess that may cover or bury the existing topography over widespread areas, Although fine and dusty to the touch, because of its high cohesion, particularly when damp, many extensive loess deposits maintain vertical walls when cut through naturally by a stream or artificially as for a road, Because of its high calcium carbonate content, loess in regions of moderate rainfall forms the parent material for many of Earth's most fertile agricultural soils

arid region geomorphology

wind-derived (eolian) geomorphic processes play an important role, but running water does more geomorphic work than the wind does in arid regions

surface creep

wind-generated transportation consisting of pushing and rolling sediment downwind in continuous contact with the surface, larger sand grains too heavy to be lifted into the air

glacier retreat

withdrawal of the toe or terminus of a glacier to a higher elevation or higher latitude due to a decrease in size, net ablation