Geology Exam 2

What covers large portions of North American and Siberia? Thawing produces unstable ground that may slide, slump, subside, and undergo severe frost heaving.

Permafrost.

Wind deposits are of what two distinct types?

(1) mounds and ridges of sand, called dunes, that are formed from sediment carried as part of the wind's bed load; and (2) extensive blankets of silt, called loess, that once were carried by wind in suspension.

What are the two general types of stream valleys?

(1) narrow V-shaped valleys and (2) wide valleys with flat floors. Because the dominant activity is downcutting toward base level, narrow valleys often contain waterfalls and rapids.

What are some of the current environmental problems involving groundwater?

(1) overuse by intense irrigation, (2) land subsidence caused by groundwater withdrawal, and (3) contamination by pollutants.

Local factors that influence shoreline erosion are?

(1) the proximity of a coast to sediment-laden rivers, (2) the degree of tectonic activity, (3) the topography and composition of the land, (4) prevailing winds and weather patterns, and (5) the configuration of the coastline and nearshore areas.

What are the various processes included under the name of mass wasting are divided and described on the basis of

(1) the type of material involved (debris, mud, earth, or rock); (2) the type of motion (fall, slide, or flow); (3) the rate of movement (rapid or slow).

What are the two dis¬tinct types of glacial drift?

(1) till, which is unsorted sed¬iment deposited directly by the ice; and (2) stratified, drift, which is relatively well-sorted sediment laid down by gla¬cial meltwater.

What are the two general types of base level (the lowest point to which a stream may erode its channel)?

(1) ultimate base level and 2) temporary, or local base level. Any change in base level will cause a stream to adjust and establish a new bal¬ance. Lowering base level will cause a stream to downcut, whereas raising base level results in deposition of materi¬al in the channel

Waves are moving energy and most ocean waves are initiated by the wind. What the three factors that influence the height, wave¬length, and period of a wave?

1) wind speed, (2) length of time the wind has blown, and (3) fetch, the distance the wind has traveled across open water.

What occur when water rises above the level at which it was initially encountered?

Artesian wells

the lifting and removal of loose material, often produces shallow depres¬sions called blowouts

Deflation

The transport of sediment by wind differs from that by run¬ning water in what two ways?

First, wind has a low density com¬pared to water; thus, it is not capable of picking up and transporting coarse materials. Second, because wind is not confined to channels, it can spread sediment over large areas. The bed load of wind consists of sand grains skipping and bouncing along the surface in a process termed saltation. Fine dust particles are capable of being carried by the wind great distances as suspended load.

What factors influence mass wasting?

Gravity, satu¬ration of the material with water, oversteepening of slopes beyond the angle of repose, removal of vegetation, and ground shaking by: earthquakes.

As a resource, _____represents the largest reservoir of fresh water that is readily available to humans. Geological¬ly, the dissolving action of ______produces caves and sinkholes. _____is also an equalizer of stream flow.

Groundwater

water that completely fills the pore spaces, in sediment and rock in the subsurface zone of saturation. The upper limit of this zone is the water table. The zone of aeration is above the water table where the soil, sediment, and rocks are not saturated

Groundwater

what involves building solid, massive structures in an attempt to protect a coast from erosion or prevent the movement of sand along the beach. s.

Hard stabilization

What does Hard stabilization in¬clude?

Hard stabilization in¬cludes -groins (short walls constructed at a right angle to the shore to trap moving sand), -breakwaters (structures built par¬allel to the shore to protect it from the force of large break¬ing waves), and -seawalls (armoring the coast to prevent waves from reaching the area behind the wall). Alternatives to hard stabilization include beach nourishment, which involves the addition of sand to replenish eroding beaches, and re¬location of damaged or threatened building

____ are not common throughout geologic history. ____ which began 2 million to 3 million years ago, was a very complex period characterized by a number of advances and withdrawals of glacial ice. Most of these major glacial episodes occurred during a division of the geologic time scale called the Pleistocene epoch. Perhaps the most con¬vincing evidence for the occurrence of several, glacial ad¬vances during the____ is the widespread existence of multiple layers of drift and an uninterrupted record of climate cycles preserved in seafloor sediments.

Ice age

what deserts coincide with the zones of sub¬tropical highs in lower latitudes?

Low-latitude deserts

What is the downslope movement of rock, re¬golith, and soil under the direct influence of gravity?

Mass wasting

what is the consistency of a glacier at the surface and below?

Near the surface of a glacier, in the zone of fracture, ice is brit¬tle. However, below about 50 meters, pressure is great, caus¬ing ice to flow like a plastic material. A second important mechanism of glacial movement consists of the entire ice mass slipping along the ground.

The interaction between streams and groundwater takes place in what three ways?

Streams gain water from the inflow of groundwater (gaining stream); they lose water through the stream bed to the groundwater system (losing stream); or they do both, gaining in some sections and losing in others.

What produces the widening of stream valleys?

The combined effects of mass wasting and erosion by running water

What describes the continuous interchange of water among the oceans, atmosphere, and continents. Pow¬ered by energy from the Sun, it is a global system in which the atmosphere provides the link between the oceans and continents. The processes involved in the hydrologic cycle include precipitation, evaporation, infiltration (the movement of water into rocks or soil through cracks and pore spaces), runoff (water that flows over the land), and transpiration (the release of water vapor to the atmosphere by plants). Running water is the single most important agent sculpturing Earth's land surface.

The hydrologic cycle

what are the shapes of dunes?

The profiles of many dunes show an asymmet¬rical shape, with the leeward (sheltered) slope being steep and the windward slope more gently inclined. The thickest and most extensive deposits of loess occur in western and northern China. Unlike the deposits in China, which originated in deserts, the loess in the United States and Europe is an indirect product of glaciation.

Two types of alluvial chan¬nels are?

Two types of alluvial chan¬nels are meandering channels and braided

How do Geyesers occur?

When groundwater circulates at great depths, it becomes heated. If it rises, the water may emerge as a hot spring. Gey¬sers occur when water quickly changes to steam, causing the geyser to erupt. The source of heat for most hot springs and geysers is hot igneous rock. Geothermal energy is harnessed by tapping natural underground reser¬voirs of steam and hot water.

Stream deposits are called _______ and may occur as channel deposits called bars, as floodplain deposits, which include natural levees, and as deltas or fans at the mouths of streams.

alluvium

What consist of materials with larger pore spaces (such as sand) that are permeable and transmit groundwater freely?

aquifers

Materials with very small pore spaces (such as clay) hinder or prevent groundwater movement and are called what?

aquitards

what is an accumulation of sediment found along the landward margin of the ocean or a lake. Among its parts are one or more berms and the beach face. These are com¬posed of whatever material is locally abundant and should be thought of as material in transit along the shore

beach

Most waves reach the shore at an angle. The uprush (swash) and backwash of water from each breaking wave moves the sediment in a zigzag pattern along the beach. This movement can transport sand hundreds or even thousands of meters each day. Oblique waves also produce longshore currents within the surf zone that flow parallel to the shore. What is it called?

beach drift

Stream channels are of two basic types?

bedrock channels and alluvial channels. Bedrock channels are most common in headwaters regions where gradients are steep. Rapids and waterfalls are common features. Two types of alluvial chan¬nels are meandering channels and braided channels

What is the hydrologic cylce powered by?

by energy from teh sun.

How do •glaciers erode land and acquire debris?

by plucking (lifting pieces of bedrock out of place) and abrasion (grinding and scraping of a rock surface). Mass-wasting processes also make significant contributions to the load of many alpine glaciers. Erosional features produced by valley glaciers in¬clude glacial troughs, hanging valleys, pater noster lakes, fiords, cirques, aretes, horns, and roches moutonnees.

The stream's ability to transport solid particles is described using what two criteria?

capacity (the maximum load of solid par¬ticles a stream can carry) and competence (the maximum par¬ticle size a stream can transport). Competence increases as the square of stream velocity, so if velocity doubles, water's force increases fourfold.

what forms in limestone at or below the water table when acidic groundwater dissolves rock along lines of weakness, such as joints and bedding planes. The various dripstone features found in caverns are collectively called speleothems. Landscapes that to a large extent have been shaped by the dissolving power of groundwater exhibit karst topography, an irregular terrain punctuated with many depressions, called sinkholes or sinks

caverns

What does the slowest forms of mass wasting include? It's the grad¬ual downhill movement of soil and regolith, and solifluction, the gradual flow of a saturated surface layer that is under¬lain by an impermeable zone. Common sites for solifluction include regions underlain by permafrost (permanently frozen ground associated with tundra and ice-cap climates).

creep.

What is a relatively rapid flow of soil and regolith con¬taining a large amount of water; and earthflow, an unconfined flow of saturated, clay-rich soil that most often occurs on a hillside in a humid area following heavy precipitation or snow melt?

debris flow

In portions of many deserts, the sur¬face is a layer of coarse pebbles and gravels too large to be moved by the wind called what?

desert pavement

What is the land area that contributes water to a stream? these are separated by imaginary lines called what?

drainage basin; divides

Any sediment of glacial origin is called what?

drift

When a stream has cut its channel closer to base level, its en¬ergy is directed from side to side, and erosion produces what?

flat valley floor, or floodplain. Streams that flow upon flood plains often move in sweeping bends called meanders. Wide¬spread meandering may result in shorter channel segments, called cutoffs, and/or abandoned bends, called oxbow lakes.

what are thick mass of ice originating on the land from the compaction and recrystallization of snow, and it shows evidence of past or present flow?

glacier

What are the factors that determine a stream's velocity?

gradient (slope of the stream channel), shape, size, and roughness of the channel and the stream's discharge (amount of water passing a given point per unit of time frequently measured in cubic feet per second). Most often, the gradient and roughness of a. stream decrease downstream, while width, depth, discharge, and velocity increase.

What are floods triggered by?

heavy rains and/or snowmelt. Some¬times human interference can worsen or even cause floods. Flood-control measures include the building of artificial lev¬ees and dams, as well as channelization, which could involve creating artificial cutoffs. Many scientists and engineers ad¬vocate a nonstructural approach, to flood control that in¬volves more appropriate land use.

Where do glaciers form?

in areas where more snow falls in winter than melts during summer. Snow accumulation and ice forma¬tion occur in the zone of accumulation. Its outer limits are de¬fined by the snowline. Beyond the snowline is the zone of wastage, where there is a net loss to the glacier. The glacial budget is the balance, or lack of balance, between accumu¬lation at the upper end of the glacier, and loss, called ablation, at the lower end

How does groundwater move?

in looping curves that are a compro¬mise between the downward pull of gravity and the ten¬dency of water to move toward areas of reduced pressure.

How do streams transport their load of sediment?

in solution (dissolved load), in suspension (suspended load), and along the bottom of the channel (bed load). Much of the dissolved load is contributed by groundwater. Most streams carry the greatest part of their load in suspension.

Features produced by shoreline erosion?

include wave-cut cliffs (which originate from the cutting action of the surf against the base of coastal land), wave-cut platforms (relatively flat, bench like surfaces left behind by receding cliffs), sea arches (formed when a headland is eroded and two caves from opposite sides unite), and sea stacks (formed when the roof of a sea arch collapses).

What happens when a wave travels into shallow water

it ex¬periences physical changes that can cause the wave to col¬lapse, or break, and form surf

The quantity of water that can be stored in a material de¬pends upon what?

its porosity (the volume of open spaces). The permeability (the ability to transmit a fluid through inter¬connected pore spaces) of a material is a very important fac¬tor controlling the movement of groundwater.

what deserts exist principally because of their positions in the deep interiors of large landmasses far removed from the ocean?

middle-latitude deserts

what are the most widespread features created by glacial deposition are layers or ridges of till?

moraines

Processes involved in hydrologic cylce?

precipitation, evaporation, infiltration (the movement of water into rocks or soil through cracks and pore spaces), runoff (water that flows over the land), and transpiration (the release of water vapor to the atmosphere by plants)

what is responsible/or most of the erosional work in a desert?

running water

What is the single most important agent in sculpting Earth's land surface>

running water.

What does the more rapid forms of mass wasting include? It's the downward sliding of a mass of rock or unconsolidated ma¬terial moving as a unit along a curved surface; rockslide, blocks of bedrock breaking loose and sliding downslopeWhat is slump? What does it relate to?

slump

Streams deposit sediment when velocity slows and compe¬tence is reduced. What does this result in? It's the process by which like-sized particles are deposited together

sorting

Some of the depositional features formed when sediment is moved by beach drift and longshore currents are what?

spits (elon¬gated ridges of sand that project from the land into the mouth of an adjacent bay), baymonth bars (sandbars that completely cross a bay), and tombolas (ridges of sand that connect an island to the mainland or to another island). Along the Atlantic and Gulf coastal plains, the shore zone is characterized by barrier islands, low ridges of sand that par¬allel the coast at distances from 3 to 30 kilometers offshore.

Many of the landscapes of the Basin and Range region of the western and southwestern United States are the result of what?

streams eroding uplifted mountain blocks and depositing the sedi¬ment in interior basins. Alluvial fans, playas, and playa lakes are features often associated with these landscapes

Tides, the daily rise and fall in the elevation of the ocean surface, are caused by what?

the gravitational attraction of the Moon and, to a lesser extent, by the Sun. Near the times of new and full moons, the Sun and Moon are aligned, and their gravitational forces are added together to produce espe¬cially high and low tides. These are called the spring tides. Conversely, at about the times of the .first and third quarters of the Moon, when the gravitational forces of the Moon and Sum are at right angles, the daily tidal range is less. These are called neap tides.

The amount of water running off the land rather than sinking into the ground depends upon what?

the infiltration capacity of the soil. Initially runoff flows as broad, thin sheets across the ground, appropriately termed sheet flow. After a short distance, threads of current typically develop and tiny channels called rills form

In addition to massive erosional and depositional work, what other effects of Ice Age glaciers includes?

the migration, of organisms, changes in stream courses, adjustment of the crust by rebounding after the removal of the immense load of ice, and climate changes caused by the existence of the glaciers themselves. In the sea, the most far-reaching effect, of the Ice Age was the worldwide change in sea level that accompa¬nied each advance and retreat of the ice sheets.

The primary factors influencing the velocity of groundwater flow are what?

the slope of the water table (hydraulic gradient) and the permeability of the aquifer (hydraulic conductivity.)

Although wind erosion is more significant in dry areas than elsewhere, what is the main role of wind in a desert?

the transportation and deposition of sediment.

What are the three main parts of river systems?

the zones of ero¬sion, transportation and deposition.

Wind also erodes by abrasion, sometimes creating interestingly shaped stones termed what?

ventifacts

Wave erosion is caused by what?

wave impact pressure and abrasion (the sawing and grinding action of water armed with rock fragments).

The bending of waves is called what? Owing to refraction, ___ is concentrated against the sides and ends of headlands.

wave refraction

what occurs when openings bored into the zone of saturation, withdraw groundwater and create roughly conical depressions in the water table known as cones of depression

wells

When do streams deposit sediment?

when velocity slows and competence is reduced.

When do springs occur?

whenever the water table intersects the land surface and a natural flow of groundwater results