GEOG 110 FINAL EXAM

Hydration and Hydrolysis

-Chemical decomposition of rock by water can occur by the simple combination of water with a mineral, in the process of hydration, and by the chemical reaction of water with a mineral, in the process of hydrolysis. -Hydration meaning combination with water, involves little chemical change. When some minerals undergo hydration, they expand, creating a strong mechanical wedging effect that stresses the rock forcing grains apart in a physical weathering process

Hyrdology

-Earth's rivers and waterways form vast arterial networks that drain the continents, and at any moment, approx 1250 km cubed of water is flowing through them -even though this volume is only 0.003% of all freshwater, the work performed by this energetic flow makes it a dominant natural agent of landmass denudation. Rivers shape the landscape by removing the products of weathering, mass movement, and erosion and transporting them downstream. Rivers also serve society in many ways. They not only provide us with essential water supplies, but also receive, dilute, and transport wastes, provide critical cooling water for industry, and form critical transportation networks. -of the world's rivers those with the greatest discharge (the streamflow volume past a point in a given unit of time) are the Amazon of South America, the Congo of Africa, the Yangtze of Asia, and the Orinoco of South America -In North America, the greatest discharges are from the Missouri-Ohio-Mississippi, Saint Lawrence, and Mackenzie River systems -Hydrology is the science of water and its global circulation, distribution, and properties--focusing on water at and below Earth's surface

Flow characteristics and channel deposit relationship

-a cross-sectional view of a meandering stream channel shows the flow characteristics that produce the channel deposits typical of these streams -in a straight channel or section of channel, the greatest flow velocities are near the surface at the center, corresponding to the deepest part of the stream -velocities decrease closer to the sides and bottom of the channel because of the frictional drag on the water flow -as the stream then straightens, the maximum velocity shifts back to the outside of that meander curve -thus the portion of the stream flowing at maximum velocity moves diagonally across the stream from bend to bend

Waning slope

-a debris slope grades into a waning slope, a concave surface along the base of the slope

Debris slope

-a downslope from the free face is a debris slope -receives rock fragments and materials from above -the condition of a debris slope reflects the local climate -in humid climates, continually moving water carries material away, lowering the angle of the debris slope -in arid climates, debris slopes accumulate material

Dynamic equilibrium approach to understanding landofrms

-a landscape is an open system, with highly variable inputs of energy and materials -Sun provides radiant energy that converts into heat energy that drives the hydrologic cycle and other Earth systems -the hydrologic cycle imparts kinetic energy through the mechanical motion of moving air and water -chemical energy is avaible from the atmosphere and various reactions within the crust -in addition, uplift of the land by tectonic processes create potential energy of position as land rises above sea level -as landscapes and the forces acting on them change, the surface constantly responds in search of equilibrium -every change produces compensating actions and reactions -tectonic uplift creates disequilibrium, an imbalance between relief and the energy required to maintain stability. -the idea of landscape formation as a balancing act between uplift and reduction by weathering and erosion is the dynamic equilibrium model -landscapes in a dynamic equilibrium show ongoing adaptations to the every-changing conditions of local relief, rock structure, and climate

Stream discharge

-a mass of water situated above base level in a stream has potential energy -as the water flows downslope, or downstream, under the influence of gravity, this energy becomes kinetic energy -the rate of this conversion from potential kinetic energy determines the ability f the stream to do geomorphic work and depends in part on the volume of water involved -a stream's volume of flow per unit of time is its discharge and is calculated by multiplying the channel width by the channel depth by the stream velocity -as discharge increases, one or more of the other vairables must also increase -how these variables interact depends on the climate and geology of the fluvial system

Channel patterns

-a number of factors, including the sediment load, affect the channel pattern -multiple-thread channels, either braided or anabranching, tend to occur in areas with abundant sediment or in the lowest reaches of large river systems -single-thread channels are either straight or meandering -straight channels tend to occur in headwater areas where gradient is high -in lower-gradient areas with finer sediments, meandering is more common; this is the classic river pattern in which a single channel curves from side to side in a valley or canyon

Creep

-a persistent, gradual mass movement of surface soil is soil creep -in creep, individual soil particles are lifted and disturbed, whether by the expansion of soil moisture as it freezes, by cycles of moistness and dryness, by diurnal temperature variations, or by grazing livestock or digging animals -in the freeze-thaw cycle, particles are lifted at right angle to the slope by freezing soil moisture -when the ice melts, however, the particles fall straight downward in response to gravity. As the process repeats, the surface soil gradually creeps its way downslope -the overall wasting of a creeping slope may cover a wide area -various strategies are used to arrest creep slopes, grading the terrian, building terraces, and retaining walls, planting ground cover, etc. but creep is persistent -in polar regions and high elevations, freeze-thaw processes are critical for mass wasting. During the summer when the upper layers of soil thaw and become saturated, slow downslope movement occurs, called solifluction

Drainage patterns/drainage density

-a primary feature of any drainage basin is its drainage density, determined by dividing the total length of all stream channels in the basin by the area of the basin -the number and length of channels in a given area reflect the landscape's regional geology and topography -the drainage pattern is the arrangement of channels in an area -patterns are quite distinctive and are determined by a combination of regional steepness and relief; variations in rock resistance, climate, and hydrology; and structural controls imposed by the underlying rocks -consequently, the drainage pattern of any land area on Earth is a remarkable visual summary of every geologic and climatic characteristic of that region

Stable slopes vs unstable slopes

-a slope is stable if its strength exceeds the denudation processes and unstable if its material are weaker than these processes

Continental divides

-a special class of drainage divides, continental divides, separate basins that empty into different bodies of water surrounding a continent; for North America, these bodies are the Pacific, the Gulf of Mexico, the Atlantic, Hudson Bay, or the Arctic Ocean

Landlsides

-a sudden rapid movement of a cohesive mass of regolith or bedrock that is not saturated with moisture is a landslide (a large amount of material failing simultaneously) -surprise creates danger, for the downward pull of gravity wins the struggle for equilibrium in an instant -to eliminate the element of surprise, scientists are using the GPS to monitor landslide movement -slides occur in one of two basic forms: translational or rotational

Oxbox lake

-after the former meander becomes isolated from the rest of the river, the resulting oxbox lake may gradually fill with organic debris and silt or may again become a part of the river when it floods

Slope Angle and forces

-all mass movement occur on slopes under the influence of gravitational stress -the grains will flow downslope until equilibrium is achieved -the steepness of the resulting slope, is called the angle of repose and depends on the size and texture of the grains -this angle represents a balance of the driving force (gravity) and resisting forces (friction and shear) -the angle of repose for various materials ranges between 33 degrees and 37 degrees from horizontal, and between 30 degrees and 50 degrees for snow avalanches

Physical weathering

-also known as mechanical weathering -the disintegration of rock wihtout any chemical alteration -by breaking up rock, physical weathering may operate -physical weathering occurs primarily by frost action, salt-crystal growth, and exfoliation

Single-thread channels: meandering stream

-although perfectly straight channels are rare or nonexistent in nature, many streams in steep mountain regions or in bedrock-controlled channels have a relatively straight channel pattern -often these are high-gradient streams and have such low sinuosity that they cannot be classified as typical, meandering streams (sinuosity is the ratio between the distance between 2 points measured along a stream as it curves ad the shortest, straight line distance between the same two points) -where channel slope is gradual, streams develop a more sinuous snakelike form, weaving back and forth across the landscape in a meandering stream pattern and aquiring distinctive flow and channel characteristics -the tendency to meander is evidence of a river system's propensity (like any natural system) to find the path of least effort toward a balance between self-equilibrating order and chaotic disorder

Differential weathering

-an assortment of weathering processes have worked in combo with the differing resistances of the rocks to produce differentially weathered rocks, where a more resistant cap rock protects supporting strata below -produces arches, windows, pedestals, and delicately balanced rocks

Annular drainage

-annular patterns occur on structural domes, with concentric patterns of rock strata guiding stream courses

Oxidation

-another type of chemical weathering that occurs when certain metallic elements combine with oxygen to form oxides -rusting -when oxidation reactions remove iron from the minerals in a rock, the disruption of the crystal structures makes the rock more susceptible to further chemical weathering

Denudation

-any process that wears away or rearranges landforms. The principal denudation processes affecting surface materials include weathering, mass movement, erosion, transportation, and deposition as produced by moving water, air, waves, and ice--all influenced by the pull of gravity

Degradation and aggradation in streams

-as flood flows build, stream energy increases and the competence of the stream becomes high enough that sediment transport occurs -as a result, the channel erodes, a process known as degradation -with the return of flows to normal, stream energy is reduced, and the sediment transport slows or stops -if the load exceeds a stream's capacity, sediment accumulates in the bed, and the stream channel builds up through deposition aka the process of aggradation

Undercut bank and point bar

-because the outer portion of each meandering curve is subject to the fastest water velocity, it undergoes the greatest erosive action, or scouring -this action can form a steep undercut bank or cutbank -in contrast, the inner portion of a meander experiences the slowest water velocity and thus is a zone of fill (or aggradation) that results in a point bar, an accumulation of sediment on the inside of a meander bend -as meanders develop, these scour-and-fill processes gradually work at stream banks, causing them to move laterally across a valle--this is the process of lateral erosion -as a result, the landscape near a meandering river bears marks called meander scars that are the residual deposits from previous river channels

Parent rock/ parent material

-bedrock is known as the parent rock from which weathered regolith and soils develop -wherever a soil is relatively young, its parent rock is traceable through similarities in composition -parent material is the consolidated or unconsolidated material from which soils develop, ranging from unconsolidated sediments and weathered rock to bedrock

Caves and caverns

-caves are defined as natural underground areas large enough for humans to enter -caves form in limestone because it is so easily dissolved by carbonation; any large cave formed by chemical processes is a cavern -caves generally form just beneath the water table, where later lowering of the water level exposes them to further development -speleothems are formations consisting of mineral deposits inside caves and occur in various characteristic shapes -dripstones are speleothems formed as water containing dissolved minerals slowly drips from the cave ceiling -calcium carbonate precipitates out of the evaporation solution, literally one molecular layer at a time, and accumulates on the floor below -dripstones are depositional features also known as stalactites growing from the ceiling and stalagmites growing from the floor -flowstones are sheet-like formations of calcium and carbonate on cave floors and walls

Dissolution of Carbonates

-chemical weathering also occurs when a mineral dissolves into solution (salt into water) -water vapor readily dissolves carbon dioxide thereby yielding precipitation containing carbonic acid -this acid is strong enough to dissolve many minerals especially limestone, by a type of reaction called carbonation this type of chemical weathering breaks down minerals that contain calcium, magnesium, potassium, or sodium -when rainwater attacks formations of limestone (mainly calcium carbonate) the constituent minerals dissolve and wash away with the mildly acidic rainwater -in environments where adequate water is available for dissolution, weathered limestone and marble take on a pitted and worn appearance -acid precipitation also enhances carbonation processes

Spheroidal Weathering

-chemical weathering that softens and rounds the sharp edges and corners of jointed rock as water penetrates the joints and dissolves weaker minerals or cementing materials -spheroidal weathering of a rock resembles exfoliation, but it does not result from pressure-release jointing

Microscale weathering

-complex relationship between climate and weathering -at the small scale of actual reaction sites on the rock surface, both physical and chemical weathering processes can occur over a wide range of climate types. -at this scale, soil moisture (hygroscopic water and capillary water) activates chemical weathering processes even in the driest landscape -similarly the role of bacteria in weathering is important new area of research

Suspended load

-consists of fine-grained clastic particles (bits and pieces of rock) -they are held aloft in the stream until the stream velocity slows to near zero, at which point even the finest particles are deposited -turbulence in the water, with random upward motion, is an important mechanical factor in holding a load of sediment in suspension

Effects of dams on sediment transport

-dams disrupt natural river discharge and sediment regimes, usually with detrimental effects on river systems -the flood releases of retired dams disrupts ecosystems and erodes some sediment deposits even while building up others -with such a limited sediment supply, not enough sediment is present in the system to build beaches and improve habitat even when high discharge occurs

Streams as political boundaries

-danube river -mississippi river -can change during floods

Hydrograph: annual hydrographs, storm hydrographs

-discharge changes over time at any given channel cross section -a graph of stream discharge over time for a specific location is a hydrograph -the time scale of a hydrograph can -annual hydrographs show discharge over the course of an entire year, usually with the highest discharge occurring during the spring snowmelt season -storm hydrographs may cover only a period of days, reflecting changes in discharge caused by specific precipitation events that lead to local flooding

Changes in discharge over time

-discharge varies throughout the year for most streams, depending on precipitation and temperature -rivers and streams in arid and semiarid regions may have perennial, ephemeral, or intermittent discharge

Drainage basins as open systems

-drainage basins are open systems -inputs include precipitation and the minerals and rocks of the regional geology -energy and materials are redistributed as the stream constantly adjusts to its landscape -system outputs of water and sediment dispese through the mouth of the stream or river, into a lake, another stream or river, or the ocean -change that occurs in any portion of a drainage basin can affect the entire system -if a stream is brought to a geomorphic threshold where it can no longer maintain its present form, the river system may become destabilized, initiating a transition period to a more stable condition -a river system constantly struggles toward equilibrium among the interacting variables of discharge, channel steepness, channel shape, and sediment load

Trellis drainage

-drainage pattern characterized by dipping or folded topography -such drainage is seen in the nearly parallel mountain folds of the Ridge and Valley province in the eastern US -here drainage patterns are influenced by folded rock structures that vary in resistance to erosion -parallel structures direct the principal streams, while smaller dendritic tributary streams are at work on nearby slopes, joining the main streams at right angles as in plant trellises

Stream competence and stream capacity

-during a flood (a high flow that overtops the channel banks), a river may carry an enormous sediment load, as larger material is picked up and carried by the enhanced flow -the competence of a stream is its ability to move particles of a specific size and is a function of stream velocity and the energy available to move materials -the capacity of a stream is the total possible sediment load that it can transport and is a function of discharge; thus, a large river has higher capacity than a small stream

Scarification

-human impacts that move sediment, soil, and rock material -the disposal of tailings (mined ore of little value) and waste material is a significant issue at mines -such large excavations produce tailing piles that are unstable and susceptible to further weathering, mass wasting, or wind dispersal -additionally, the leaching of toxic chems from tailings and waste piles poses an ever increasing problem for streams, aquifers, and public health across the country -Where underground mining is common, particularly for coal in the Apps, land subsidence and collapse may produce mass movement on hillslopes.

Base flow/peak flow

-during dry periods, the low discharge is described as base flow and is largely maintained by input from local groundwater -when rainfall occurs in some portion of the watershed, the runoff is concentrated in streams and tributaries in that area -the amount, location, and duration of the rainfall episode determine the peak flow, the highest discharge that occurs during a precipitation event - the nature of the surface in a watershed, whether permeable or impermeable, affects peak flow and the timing of changes recorded in the hydrograph -in deserts, where surfaces have thin, impermeable soils and little vegetation, runoff can be high during rainstorms -a rare or large precipitation event in a desert can fill a stream channel with a torrent known as a flash flood -these channels may fill in a few minutes and surge briefly during and after a storm

Geomorphic threshold

-endogenic events, such as faulting or a volcanic eruption, or exogenic events, such as a heavy rainfall or a forest fire may change the relationships between landscape elements and within landscape systems. 0during or following a destabilizing event, a landform system sometimes arrives at a geomorphic threshold or tipping point, where the system lurches to a new operational level. This threshold is reached when a geomorphic system moves form the slow accumulation of small adjustments (steady-state equilibrium) to a point of abrupt change that takes it to a new system state (dynamic equilibrium) -after crossing this threshold, the system establishes a new set of equilibrium relationships

Initial landscapes and sequential landscapes

-endogenic processes such as tectonic uplift and volcanic activity, building land forms into initial landscapes -exogenic processes tear landforms down, developing sequential landscapes characterized by lower relief, gradual change, and stability -these countering sets of processes happen simultaneously

Salt-Crystal growth (salt weathering)

-especially in arid climates where heating is intense, evaporation draws moisture to the surface of rocks, leaving behind previously dissolved minerals in the form of crystals (a process called crystallization) -over time, as the crystals accumulate and grow, they exert a force great enough to separate the grains making up the rock and begin breaking the rock pieces, a process known as salt-crystal growth or salt weathering

Conditions for slope failure

-failure can occur when a slope becomes saturated by a heavy rainfall; when a slope becomes oversteeped 40 degrees to 60 degrees in slope angle -water content is an important factor for slope stability; an increase in water content may cause rock or regolith to begin to flow -clay surfaces are highly susceptible to hydration (physical swelling in response to the presence of water) -when clay surfaces are wet, the deform slowly in the direction of movement, when saturated, they form viscous fluid that fails easily with overlying weight -the shocks and vibrations associated with earthquakes often case mass movement

Channel incision

-fluvial erosion by hydraulic action and abrasion causes streams to erode downward (deepen), erode laterally (widen), and erode in an upstream direction (lengthen) -the process whereby streams deepen there channel is known as channel incision

Formations of Karst

-for a limestone landscape to develop into karst topography, several conditions are necessary: -the limestone formation must contain 80% or more calcium carbonate for dissolution processes to proceed effectively -complex patterns of joints in otherwise impermeable limetsone are needed for water to form routes to subsurface drainage channels -an aerated (air-containing) zone must exist between the ground surface and the water table -vegetation cover is needed to supply varying amounts of organic acids that enhance the dissolution process -the role of climate in providing optimum conditions for karst processes remains under debate, although the amount and distribution of rainfall appear important -the karst features found today in arid regions were formed during past climatic conditions of greater humidity -karst is rare in the Artctic and Antarctic regions because subsurface water, although present there, is generally frozen -as with all weathering processes, time is an important factor, karst landscapes are thought to be locally unique

Driving force

-gravity -it works in conjuction with weight, size, and shape of the surface material -the degree to which the slope is oversteepened (how far it exceeds the angle of repose) and the amount and form of moisture available (frozen or fluid) -the greater the slope angle, the more susceptible the surface material is to mass-wasting processes -the resisting force is the strength of the slope material, that is, its cohesiveness and internal friction which work against gravity and mass wasting, which eventually reaches the point at which gravity overcomes friction, initiating slope failure

Sediment transport during a flood

-greater discharge increases flow velocity and therefore the competence of the river to transport sediment as the flood progresses. As a result, the river's ability to scour materials from its bed is enhanced -this type of channel adjustment is ongoing, as the system continuously works toward equilibrium, maintaining a balance between discharge, sediment load, and channel form

Human activities impact on patterns of discharge

-human activities have enormous impact on patterns of discharge in a drainage basin -a hydrograph for a specific portion of a stream changes after a disturbance such as a forest fire or urbanization of the watershed, with peak flows occurring sooner during the precipitation event -the effects of urbanization are quite dramatic, both increasing and hastening peak flow -urban areas produce runoff patterns quite similar to those of deserts, since the sealed surfaces of the city drastically reduce infiltration and soil-moisture recharge -these issues will intensify as urbanization continues

Drainage divides

-in any drainage basin, water initially moves downslope as overland flow, which takes two forms: it can move as sheetflow, a thin film spread over the ground surface, and it can concentrate in rills, small scale grooves in the landscape made by the downslope movement of water -rills may develop into deeper gullies and then into stream channels leading to the valley floor -the high ground that separates one valley from another and directs sheetflow is called and interfluve -ridges act as drainage divides that define the catchment (water-receiving area) of every drainage basin, such ridges are the dividing lines that control into which basin the surface runoff drains

Classes of Mass movement

-in any mass movement, gravity pulls on a mass of material until the critical shear-failure point is reached--a geomorphic threshold -the material then can fall, slide, flow, or creep--the four classes of mass movement -these classes range in volume of materials (small to massive), moisture content (dry to wet) and rate of movement (rapid free-falling rock to slow-moving creep)

Karst topography

-in certain areas of the world with extensive limestone formations, chemical weathering involving dissolution of carbonates dominates entire landscapes -these areas are characterized by poor surface drainage, pitted bumpy surface topography, solution channels (dissolved openings and conduits) underground. In landscapes of this type, weathering and erosion caused by groundwater may results in remarkable mazes of caverns -these are the hallmark features and landforms of karst topography -approx 15% of Earth's land area has some karst features

Regolith

-in most areas, the upper surface of bedrock undergoes continual weathering, creating broken-up rock called regolith -as regolithg continues to weather, or is transported and deposited, the loose surface material that results becomes the basis for soil development

Changes in discharge with distance downstream

-in most river basins in humid regions, discharge increases in a downstream direction the Mississippi River is typical, beginning as many small streams that merge successifvely with tributaries to form a large-volume river ending in the Gulf of Mexico -however, if a stream originates in a humid region and subsequently flows through an arid region, this relationship may change -high potential evapotranspiration rates in arid regions can cause discharge to decrease with distance downstream, a process that is often exacerbated by water removal for irrigation -a river is depleted by high evapotranspiration and removal of water for agriculture and municipal uses; shifting climatic patterns are add to a river's water losses -as discharge increases in a downstream direction, velocity usually increases, stream veolicty is affected by friction between the flow and the roughness of the channel bed and banks -friction is highest in shallow mountain streams with boulders and other obstacles that add roughness and slow the flow -in streams where contact with the bed and banks is high or where the channel is rough as in sections of rapids, turbulent flow occurs and most of the stream's energy is expended in turbulent eddies -in wide, lowland rivers, where friction is reduced by less contact of the flow with the bed and banks, the apparent smoothness and quietness of the flow mask the increased velocity -the energy of these rivers is enough to move large amounts of sediment

Tropical karst

-in tropical climates, karst topography includes two characteristic landforms (cockpits and cones) -weathering in these wet climates where thick beds of limestone are deeply jointed exposing a large surface area for dissolution processes, forms a complex topography called cockpit karst, resembling the shape of an egg-carton -the cockpits are steep-sided star-shaped hollows in the landscape with water drainage occurring by percolation from the bottom to the underground water flow -sinkholes may form in the cockpit bottoms -dissolution weathering in the tropics also leaves isolated resistant limestone blocks that form cones known as karts towers.

Translation slides vs rotational slides

-involve movement along a planar flat surface roughly parallel to the angle of the slope, with no rotation -rotational slides, also called slumps, occur when surface material moves along a concave surface. Frequently, underlying clay presents an impervious barrier to percolating water. as a result, water flows along the clay's surface, undermining the overlying block. The overlying material may rotate as a single unit, or it may acquire a stepped appearance. -unrestricted irrigation of lawns causes gardens feeding drainage runoff water into subsurface strata to increase instability and lubricate slides

Mass-movement processes/mechanics

-mass movement is also known as mass wasting, in which a downslope movement of a body of material made up of soil, sediment, or rock propelled by the force of gravity occurs -mass movements can occur on land or beneath the ocean as submarine landslides

Slopes

-material loosened by weathering is susceptible to erosion and transportation -however, for material to move downslope, the forces of erosion mus to overcome other forces: friction, inertia (the resistance to movement) and the cohesion of particles to one another. If the angle is steep enough for gravity to overcome firctional forces, or if the impact of raindrops or moving animals or even wind dislodges material, then erosion of particles and transport downslope can occur. -Slopes, or hillslopes, are curved, inclined surfaces that form the boundaries of landforms -the basic components of a slope vary with conditions of rock structure and climate -slopes generally feature an upper waxing slope near the top (waxing means increasing) -this convex surface curves downward and may grade into a free face below, a steep scarp or cliff whose presence indicates an outcrop of resistant rock

Cutoff

-meandering streams create a remarkable looping pattern on the landscape -actively meandering streams eroe their outside banks as they migrate, often forming a narrow neck of land that eventually erodes through the and forms a cutoff -a cutoff marks an abrupt change in the stream's lateral movements-the stream becomes straighter

Hydrolysis

-the decomposition of a chemical compound by reaction with water -in geomorphology, hydrolysis is of interest as a process that break downs silicate minerals in rocks -in contrast with hydration, in which water merely combines with minerals in the rock, hydrolysis chemically breaks down a mineral, thereby producing a different mineral through the chemical reaction -when minerals in rock are changed by hydrolysis, the interlocking crystal network consolidating the rock breaks down and granular disintegration takes place. Such disintegration in granite may corrode the rock and crumble it

Measuring discharge

-measurements of width, depth, and velocity are needed at a stream cross section in order to calculate discharge -field measurements of these variables may be difficult to obtain, depending on a stream's size and flow -the common practice is to measure velocity for different subsections of the stream cross section, using a movable current meter -width and depth for each subsection are then combined with velocity to compute subsection discharge, and then all the subsection discharges for the cross section are totaled -since channel beds are often composed of soft sediments that may change over short time periods, stream depth is measured as the height of the stream surface above a constant reference elevation (a datum) and is called the stage -scientists use a staff gage (a pole marked with water levels or a stilling well) on the stream bank with a gage mounted in it to measure stage

Mountaintop removal

-mining done by removing ridges and summits and dumping the debris into stream valleys, thereby exposing the coal seams for mining and burying the stream channels -stream valleys filled affect downstream water quality with concentrations of water potentially toxic nickel, lead, cadmium, iron, and selenium that generally exceed gov't standards

Superposed stream

-occasionally, drainage patterns occur that seem discordant with the landscape through which they flow -for example, a drainage system may initially develop over horizontal strata that have been deposited on top of uplifted, folded structures -as the streams erode into the folded strata, they keep their original course, downcutting into the rock in a pattern contrary to its structure -such a stream is a superposed stream in which a preexisting channel pattern has been imposed upon older underlying rock structures

Bedrock

-on a typical hillside, loose surface material such as gravel, sand, clay, or soil overlies consolidated or solid rock called bedrock

Rectangular drainage/parallel drainage

-parallel drainage is associated with steep slopes -rectangular drainage is formed by a faulted and jointed landscape, which directs stream courses in patterns of right-angle

Derange drainage

-pattern with no clear geometry and no true stream valley occurs in areas such as the glaciated shield regions of Canada, northern Europe, and some parts of Michigan and other states

Perennial streams, ephemeral streams, intermittent streams

-perennial flow all year, fed by snowmelt, rainfall, groundwater, or some combo of those sources -ephemeral streams flow only after precipitation events and are not connected to groundwater systems. Years may pas between flow events in these usually dry stream channels -intermittent streams flow for several weeks or months each year and may have some groundwater inputs

Fluvial processes

-processes that are related expressly to streams and rivers are termed fluvial -there is some overlap in usage between the terms river and stream -specifically, the term river is applied to the trunk or main stream of the network of tributaries forming a river system -stream is a more general term for water flowing in a channel and is not necessarily related to size -fluvial systems, like all natural systems, have characteristic processes and produce recognizable land forms, yet also can behave with randomness and seeming disorder

Bed load/traction/saltation

-refers to coarser materials that are moved by traction, which is the rolling or dragging of materials along the streambed, or by saltation, a term referring to the way particles may bounce along in short hops and jumps -particles transported by saltation are too large to remain in suspension but are not confined to the sliding and rolling motion of traction -stream velocity affects these processes, particularly the stream's ability to retain particles in suspension -with increased kinetic energy in a stream, parts of the bed load are rafted upward and become suspended load

Chemical weathering

-refers to the chemical breakdown, always in the presence of water, of the constituent minerals in rock -the chemical decomposition and decay become more intense as both temperature and preciptiation increase -although individual inerals vary in susceptibility, all rock-forming minerals are responsive to some degree of chemical weathering -familiar example of chemical weathering is the eating away of cathedral facades and the etching of tombstones by acid precipitation

Induced seismicity

-reservoirs may be connected to earthquake activity in tectonically active southwest CHina

Radial drainage

-results when streams flow off a central peak or dome, such as occurs on a volcanic mountain

Stream restoration

-river restoration -the process that reestablishes the health of a fluvial ecosystem including channel processes and form, riprarian vegetation, and fisheries -every stream restoration project has a particular focus, which varies with the problems and impacts on that particular stream -common restoration goals are to reinstate instream flows, restore fish passage, prevent bank erosion, and reestablish vegetation along the channel or on the floodplain -the scale of a stream restoration varies from a few kilometers of stream to hundreds of miles of river to an entire watershed -stream restoration involves the cooperation of numerous landowners and regulating agencies within a watershed, also involves balancing different water use needs with drainage basin needs

Interruptions to water and sediment flows

-rivers move both water and sediment, a process that builds fertile soils on valley floors and in the flatlands where rivers meet the sea -dams interrupt this process, starving downstream areas of sediment and nutrients that naturally replenish farmland in the cycle of annual spring floods in the cycle of annual spring floods -sediment is also critical for maintaining stream habitat, as well as coastal wetlands near the river's mouth. When sediment is trapped behind a dam, excessive erosion often results downstream, leading to degradation of banks and the riverbed. Alterations to water and sediment movement also have detrimental effects on fisheries, which are critical food resources for populations in the downstream portions of the river system

Factors influencing weathering process

-rock composition and structure (jointing). The character of the bedrock (hard or soft, soluble or insoluble, broken or unbroken) and its mineral composition (different minerals weather at different rates) influence the rate of weathering. Joints are fractures or separations in rock that occur without displacement of the rock on either side (in contrast with faulting). Jointing increases the surface area of rock exposed to both physical and chemical weathering -climate (precipitation and temperature). Wetter environments are warmer and speed up chemical weathering processes, colder environments have freeze-thaw cycles that cause physical weathering. Rocks that weather rapidly in warm, humid climates may be resistant to weathering in dry climates (an example is limestone) -slope orientation: whether a slope faces north, south, east, west controls the slope's exposure to the Sun, wind, and precipitation. Slopes facing away from the Sun's rays tend to be cooler, moister, and more vegetated than are slopes in direct sunlight. This effect of orientation is especially noticeable in the middle and higher latitudes. -Subsurface water: the position of the water table and the water movement within soil and rock structures influence weathering -vegetation: although vegetative cover can protect rock by shielding it from raindrop impact and providing roots to stabilize soil, it also produces organic acids from the partial decay of organic matter, that contribute to chemical weathering. Moreover, plant roots can enter crevices and mechanically break up a rock, exerting enough pressure to force rock segments apart thereby exposing greater surface area to other weathering processes. -time: these processes require long peridos of time, usually the longer the duration of exposure for a partcular surface the more it will be weathered

Rockfalls and debris avalanches

-rockfalls and debris avalanches are types of mass movement that occur at faster rates in material that have little to intermediate water content -a rockfall is simply a volume of rock that falls through the air and hits a surface -during a rockfall, individual pieces fall independently and characteristically form cone-shaped piles of irregular broken rocks known as talus cones that coalesce in a talus slope at the base of a steep incline -a debris avalanche is a mass of falling and tumbling rock, debris, and soil traveling at high velocity owing to the presence of ice and water that fluidize the debris

Feautres of karst landscapes

-sinkholes:or dolines, weathering by the dissolution of limestone creates these -circular depressions in the ground surface that may reach 600 meter in depth -two types of sinkholes are most prominent in karst terrain -a solution sinkhole forms by the slow subsidence of surface materials along joints or at an intersection between joints. -a collapse sinkhole develops over a period of hours or days and forms when a solution sinkhole collapses through the roof of an underground cavern -these sinkholes can have dramatic features, not all of which are associated with karst processes -human activites cause many of these sinkhole subsidence events

Angle of equilibrium

-slopes are open systems and seek and angle of equilibrium among the forces -conflicting forces work simultaneously on slopes to establish a compromise incline that balances these forces optimally -when any condition in the balance is altered, all forces on the slope compensate by adjusting to a new dynamic equilibrium

Stream restoration science

-stream restoration practices have become a lucrative business for hundreds of companies throughout the US, however stream science restoration is still in infancy -given the complexities of streams and their ecosystems, some intuitive artistic license is often used when designing a stream, and not all designs withstand test of time

Basic fluvial concepts

-streams, a mixture of water and solids, provide resources and shape landforms -they create fluvial landscapes through the ongoing erosion, transport, and deposition of materials in a downstream direction -the energy of a stream to accomplish this geomorphic work depends on a number of factors including gradient, base level, and volume of flow (discharge)

Drainage basins and drainage patterns

-streams, which come together to form river systems, lie within drainage basins, the portions of landscape from which they receive their water -every stream has its own drainage basin, or watershed, ranging in size from tiny to vast -a major drainage basin system is made up of many smaller drainage basins, each of which gathers and delivers its runoff and sediment to a larger basin, eventually concentrating the volume into the main stream

Speleology

-study of caves -90% wordwide still undiscovered -cave habitats are unique, nearly closed, self-contained ecosystems with simple food chains and great stability. -in total darkness bacteria synthesize inorganic elements and produce organic compounds that sustain many types of cave life including algae, small invertebrates, amphibians, and fish -biospeleology is the study of cave organisms

Graded streams

-the changes in a river's gradient from its headwater to its mouth are usually represented in a side view called a longitudinal profile -the curve of a river's overall gradient is generally concave -a river characteristically has a steeper slope nearer the headwaters and a more gradual slope downstream -the causes of this shape are related to the energy available to the stream for transporting the load it receives -the tendency of natural systems, including streams, to move toward a state of equilibrium causes stream channels to adjust their channel characteristics over a period of year so that the flow is able to move the sediment supplied from the drainage basin -a graded stream is one in which the channel slope has adjusted, given the discharge and channel conditions, so that stream velocity is just enough to transport the sediment load -a graded stream has a characteristic longitudinal profile -any variation or bump in the profile such as the steep drop of a waterfall will be smoothed out over time as the stream adjusts toward a graded condition -attainment of a graded condition does not mean that the stream is at its lowest gradient, but rather that it has achieved a state of dynamic equilibrium between its gradient and its sediment load -this balance depends on many factors that work together on the landscape and within the river system -an individual stream can have both graded and ungraded portions, and it can have graded sections without having an overall graded slope -variation & interruptions are the rule rather than the exception -disturbances in a drainage basin, such as mass wasting on hillslopes that carries material into stream channels, or overgrazing of riparian vegetation and associated streambank instability, can cause disruptions to this equilibrium condition -the concept of stream gradation is intimately tied to stream gradient; any exchange in the characteristic longitudinal profile of a river causes the system to respond, seeking a graded condition

Hyrdaulic action

-the geomorphic work performed by a stream includes erosion and deposition, which depends on the volume of water and the total amount of sediment in the flow -Hydraulic action is a type of erosive work performed by flowing water alone, a squeeze-and-release action that loosens and lifts rocks -hydraulic action is at a maximum in upstream tributaries of a drainage basin, where sediment load is small and flow is turbulent -the downstream portions of a river, however, move much larger volumes of water past a given point and carry larger amounts of sediment -As this debris moves along, it mechanically erodes the streambed further through the process of abrasion, with rock and sediment grinding and carving the streambed like liquid sandpaper

Basel level

-the level below which a stream cannot erode its valley is base level -in general, the ultimate base level is sea level, the average level between high and low tides -base level can be visualized as a surface extending inland from sea level, inclined gently upward under the continents -in theory, this is the lowest practical level for all denudation processes -American geologist and explorer John Wesley Powell, put forward the idea of base level in 1875 -Powell recognized that not every landscape has degraded all the way to sea level; clearly other intermediate base levels are in operation -a local base level or temporary one, may determine the lower limit of local or regional stream erosion -a river or lake is a natural local base level; the reservoir behind a dam is a human-caused local base level -in arid landscape with internal drainage, valleys, plains, or other low points act as local base levels

Dissolved load

-the material that travels in solution, especially the dissolved chemical compounds derived from minerals such as limestone or dolomite or from soluble salts -the main process contributing material in solution is chemical weathering

Dendritic drainage

-the most familiar pattern of drainage is dendritic drainage -this treelike pattern is similar to that of many natural systems, such as capillaries in the human circulatory system, or the veins in leaves, or the roots of trees -energy expenditure in the moving of water and sediment through this drainage system is efficient because the total length of the branches is minimized

Fluvial processes and landforms (erosion and deposition)

-the ongoing interaction between erosion, transportation, and deposition in a system produces fluvial landscapes -erosion in fluvial systems is the process by which water dislodges, dissolves, or removes weathered surface material -this material is then transported to new locations, where it is laid down in the process of deposition -erosion, transport, and deposition are affected by discharge and channel gradient -running water is an important erosional force, and in desert landscapes it is the most significant agent of erosion even though precipitation events are infrequent

International drainage basins

-the political complexity of an international drainage basin is high -the Danube River crosses or forms part of a border of nine countries to the Black Sea -serves many economic functions: commercial transport, municipal water source, agricultural irrigation, fishing, and hydroelectric power production -the many shipping canals actually spread pollution and worsen biological conditions in the river -the river is widely regarded as one of the most polluted on Earth

Weathering

-the process that breaks down rock at Earth's surface and slightly below, either disintegrating rocks into mineral particles or dissolving it into water -weathering weakens rock surface and makes it more susceptible to the pull of gravity -physical weathering processes include the wedging action of frost in the cracks of a rock surface, and chemical weathering such as the dissolution of minerals into water

Weathering

-the process that breaks down rock by disintegrating it into mineral particles or dissolving it into water. -weathering produces an oversusceptible to other exogenic processes -the difference between weathering and erosion is important: Weathering is the breakdown of materials, whereas erosion includes the transport of weather materials to different locations -Physical (mechanical) and chemical weathering processes break up, dissolve, and generally reduce the landscape -such weathering releases essential minerals from bedrock for soil formation and enrichment

Exfoliation

-the process whereby rock peels or slips off in sheets instead of breaking up into grains is exfoliation, a term that generally refers to the removal or shedding of an outer layer -this process is also known as sheeting -exfoliation creates arch-shaped and dome-shaped features on the exposed landscape. -these exfoliation domes are probably the largest weathering features in areal extent on Earth -exfoliation is thought to occur as pressure is released from the removal of overlying rock -pressure-release jointing in which the rock cracks into joints -exfoliation is the mechanical weathering that separates the joints into layers resembling curved slabs or plates, often thinner at the top of the rock structure and thicker at the sides

Headward erosion

-the process whereby streams lengthen their channels upstream is called headward erosion -this type of erosion occurs when the flow entering a main channel has enough power to downcut, such as occurring at the break in slope where a gully enters a deep valley -headward erosion can also occur from groundwater sapping, in which groundwater seeps out of the ground at the head of the channel and weakens the channel's upstream endpoint -headward erosion can eventually cause an eroding part of one stream channel to break through a drainage divide and capture the headwaters of another stream in an adjacent valley-an event known as stream piracy

Mass movement

-the term mass movement or mass wasting is used to describe the movement of a mass of earth materials with gravity -landslides, mudflows -in areas where humans have distrubed the landscape, mass movement may occur more frequently, with disastrous consequences

Internal drainage

-the ultimate outlet for most drainage basins is the ocean -in some regions, however, stream drainage does not reach the ocean -instead, the water leaves the drainage basin by means of evaporation or subsurface gravitational flow -such basins are described as having internal drainage -regions of internal drainage occur in Asia, Africa, Australia, Mexico, and the western US, Nevada and Utah

Ultramafic minerals and weathering

-these low silica minerals such as pyroxene and olivine are most susceptible to chemical weathering -high-silica minerals such as felspar and quartz are more resistant -the chemical properties of the minerals determine the resistance of the rock to weathering

karst valleys

-through continuing dissolution and collapse, sinkholes may coalesce to form a karst valley, an elongated depression up to several kilometers long -such a valley may have bogs or ponds in sinkhole depressions and unusual drainage patterns -surface streams may even disappear to join the underground water flow typical of karst landscapes (linking to caves and cavern systems)

Sediment load/sediment transport

-when stream energy is high and a supply of sediment is present, streamflow propels sand, pebbles, gravel, and boulders downstream in the process known as sediment transport -the material carried by a stream is its sediment load, and the sediment supply relates to topographic relief, the nature of rock and soil through which the stream flows, climate, vegetation, and human activity in a drainage basin -discharge is also closely linked to sediment transport--increased discharge moves a greater amount of sediment, often causing streams to change from clear to murky brown after a heavy or prolonged rainfall -sediment is moved as dissolved load, suspended load, or bed load by four primary processes: solution, suspension, saltation, and traction

Flows

-when the moisture content of moving material is high, the suffix -flow is used as in earthflows and more fluid mudflows -heavy rains can saturate barren mountain slopes and set them moving

Frost-wedging

-when water freezes, its volume expands by as much as 9 percent. This expansion produces a powerful mechanical force that can overcome the tensional strength of rock -repeated freezing (expanding) and thawing (contracting) of water is frost action or freeze-thaw which breaks rocks apart in the process of frost wedging -the work of ice begins in small openings along existing joints and fractures, gradually expanding them and cracking or splitting them in varied shapes, depending on the rock structure. Sometimes frost wedging results in blocks of rock or joint-block separation -frost wedging is an important weathering process in the humid microthermal climates (humid continental and subarctic) and the polar climates and the in the highland climates at high elevations in mountains and worldwide.

Multiple-thread channels: braided stream and anabranching channel

-with excess sediment, a stream might become a maze of interconnected channels that form a braided stream pattern -braiding often occurs when reduced discharge lowers a stream's transporting ability, such as after flooding or when a landslide occurs upstream, or when sediment load increases in channels that have weak banks of sand or gravel -braided rivers commonly occur in glacial environments where coarse sediment is abundant (New Zealand, Alaska, Nepal, Tibet) -this pattern also occurs in wide, shallow channels with variable dischare -in large river systems, an anabranching channel pattern sometimes occurs in which multiple large channels are present across a vast floodplain

Gradient

-within its drainage basin, every stream has a degree of inclination or gradient, which is also known as the channel slope -the gradient of a stream is defined as the drop in elevation per unit distance usually measured in meters per km or feet per mile -characteristically, a river has a steeper slope nearer the headwaters and a more gradual slope downstream -a stream's gradient affects its energy and ability to move material; in particular it affects the velocity of the flow