Hewitt/Lyons/Suchocki/Yeh, Conceptual Integrated Science

Hewitt/Lyons/Suchocki/Yeh, Conceptual Integrated Science

Hewitt/Lyons/Suchocki/Yeh Conceptual Integrated Science Chapter 24 EARTHS SURFACE LAND AND WATER Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley This lecture will help you understand: A survey of Earths landforms Folds and faults and how they are classified

The different types of mountains The topography of the ocean floor Earths water and where it is found The different erosive agents that sculpt Earths surface Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Earths Many Landforms Earth consists of seven continents: Africa, Antarctica, Asia, Australia, Europe, North America, and South America Continental elevations vary between Mt. Everest (8848 m) Dead Sea shores (400 m)

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Earths Many Landforms Earth has three oceans: The Pacific Ocean Largest, deepest, and oldest The Atlantic Ocean Coldest and saltiest The Indian Ocean Smallest BUT, the oceans are all connected

In reality, there is just one big ocean. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Earths Many Landforms Continental land features High mountains, plateaus, lowland plains Ocean features Deep trenches to mid-ocean ridge system Tectonic force and landforms Folds, faults, mountains Erosive force and landforms Valleys, canyons, deltas, and floodplains

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation Deformation is a general term that refers to all changes from the original form and/or size of a rock body. Most crustal deformation occurs along plate margins. How rocks deform: Rocks subjected to stresses begin to deform. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Crustal Deformation Compressional stressconvergent plate boundary Pushing together of rock masses Tensional stressdivergent plate boundary Pulling apart of rock masses Shear stresstransform fault-plate boundary Rock masses sliding past one another Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation

Elastic deformation Size and shape deform, but rock returns to original form when stress is removed Fracture Elastic limit of rock exceeded; rock breaks Colder, surface rock Plastic deformation Elastic limit of rock exceeded; shape changed permanentlyfolds Warmer, subsurface rock Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Folds

During crustal deformation, rocks are often bent into a series of wave-like undulations called folds. Characteristics of folds: Most folds result from compressional stresses that shorten and thicken the crust. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Folds Anticlinesupfolded or arch-shaped rock layers. Oldest rock layers at the fold core, rock layers get younger away from core.

Synclinesdownfolds or trough-shaped rock layers. Youngest rocks at the fold core, rock layers get older away from the core. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Faults Strength of rock exceeded Faults are fractures with displacement. Sudden fault movement causes most earthquakes. Faults classified by relative displacement Dip-slip (vertical), strike-slip (horizontal),

or oblique Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Dip-Slip Faults Dip-slip fault movement is up or down Footwallrock below the fault surface where a miner could stand. Hanging wallrock above the fault surface where a miner could hang a lamp. Normal fault: hanging wall moves down relative to footwalltension Reverse fault: hanging wall moves up relative to footwallcompression

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Dip-Slip Faults Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Strike-Slip Faults Displacement is horizontal, right-lateral, or left-lateral depending on direction of movement. Facing the fault: Block on opposite side of fault moves to the right (right-lateral) Block on opposite side of fault moves to the left (left-lateral)

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Strike-Slip Faults Transform fault-plate boundary: Large strike-slip fault that cuts through the lithosphere, accommodates motion between two tectonic plates San Andreas Fault zonemajor transform fault separating Pacific Plate and North American Plate Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Strike-Slip Faults

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Oblique-Slip Faults Faults with combined motion: Move horizontally as in a strike-slip fault Move vertically as in a dip-slip fault Oblique faulting occurs when tensional and shear forces or compressional and shear forces exist. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation

CHECK YOUR NEIGHBOR Rocks begin to deform when they A. B. C. D. become subjected to folding and faulting. are subjected to compressional, tensional, or shear forces. break. undergo partial melting. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Crustal Deformation CHECK YOUR ANSWER Rocks begin to deform when they A. B. C. D. become subjected to folding and faulting. are subjected to compressional, tensional, or shear forces. break. undergo partial melting.

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation CHECK YOUR NEIGHBOR Rocks deform and fold in response to A. B. C. D. tensional forces that elongate the crust. tensional forces that shorten the crust.

compressional forces that elongate the crust. compressional forces that shorten the crust. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation CHECK YOUR ANSWER Rocks deform and fold in response to A. B. C. D.

tensional forces that elongate the crust. tensional forces that shorten the crust. compressional forces that elongate the crust. compressional forces that shorten the crust. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation CHECK YOUR NEIGHBOR A normal fault is created as rock in the hanging wall A. B. C.

D. drops down relative to rocks in the footwall. Tension pulls the rock apart. drops down relative to rocks in the footwall. Tension pushes the rock together. moves up relative to rocks in the footwall. Compression pulls the rock apart. moves up relative to rocks in the footwall. Compression pushes the rock together. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation CHECK YOUR ANSWER

A normal fault is created as rock in the hanging wall A. B. C. D. drops down relative to rocks in the footwall. Tension pulls the rock apart. drops down relative to rocks in the footwall. Tension pushes the rock together. moves up relative to rocks in the footwall. Compression pulls the rock apart. moves up relative to rocks in the footwall. Compression pushes

the rock together. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation CHECK YOUR NEIGHBOR A reverse fault is created as rock in the hanging wall A. B. C. D. drops down relative to rocks in the footwall. Tension pulls the rock

apart. drops down relative to rocks in the footwall. Tension pushes the rock together. moves up relative to rocks in the footwall. Compression pulls the rock apart. moves up relative to rocks in the footwall. Compression pushes the rock together. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Crustal Deformation CHECK YOUR ANSWER A reverse fault is created as rock in the hanging wall

A. B. C. D. drops down relative to rocks in the footwall. Tension pulls the rock apart. drops down relative to rocks in the footwall. Tension pushes the rock together. moves up relative to rocks in the footwall. Compression pulls the rock apart. moves up relative to rocks in the footwall. Compression pushes the rock together. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Mountains Mountains are thick sections of crust elevated with respect to the surrounding crust. Mountains are classified according to their structural features: Folded Mountains Upwarped Mountains Fault-Block Mountains Volcanic Mountains Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Folded Mountains Mountains mostly occur at convergent

plate boundariescrustal thickening causes uplift. Compression folds, thickens, and shortens the crustisostatic uplift Continental collision creates highest mountains HimalayasIndia and Eurasia AppalachiansNorth America and Africa Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Upwarped Mountains Broad upwarping of deeper rock deforms overlying sedimentary rock, producing

roughly circular structuresdomes. Older rocks are in the center, and younger rocks are on the flanks. The Black Hills of South Dakota are a large, domed structure generated by upwarping. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Fault-Block Mountains Fault-block mountains occur within large areas of broad uplift. Overall force is usually compression. But crust is also stretched in such settings, like a balloon is stretched when inflated. Another example: When a tree branch is

bent, compression occurs on the inside of the bend and tension occurs on the outside of the bend. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Fault-Block Mountains Normal faults in stretched crust let huge blocks drop downward. Block left standing is the mountain. Broad uplift continues. The Sierra Nevada Mountains The Grand Teton Mountains The Basin and Range Province The Great Basin, geographically Covers most of Nevada and parts of Arizona, California, and Utah

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Volcanic Mountains Volcanic mountains formed by eruptions of lava, ash, and rock fragments. Opening at the summit of a volcano: Crater: steep-walled depression at the summit, less than 1 km in diameter Caldera: summit depression greater than 1 km diameter, produced by collapse following a massive eruption Ventan opening connected to the magma chamber via a pipe

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Volcanic Mountains Shield volcano: Broad, large, slightly dome-shaped volcano Composed primarily of basaltic lava Mild eruptions of large volumes of lava Mauna Loa on Hawaii Cinder cone:

Ejected lava (mainly cinder-sized) fragments Steep slope angle, small in size Sunset Crater in Arizona Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Volcanic Mountains Composite cone: Large, classic-shaped volcano (thousands of feet high and several miles wide at base) Composed of interbedded lava flows and alternating layers of ash, cinder, and mud Many are located adjacent to the Pacific Ocean (Mount Fuji, Mount St. Helens) Very violent, explosive volcanic activity (Mt.

Vesuvius) Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Volcanic Mountains Most volcanoes form near plate boundaries where converging plates meet. About 75% of the worlds volcanoes are found in the Ring of Fire that encircles the Pacific Ocean. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Volcanic Mountains Hot spotsstationary, deep, very hot. Hot

mantle rock moves upward by convection. Hot spot volcanism: Partial melting occurs near the surface Localized volcanism in the overriding plate In oceanic crust, basaltic magma produced Hawaiian Islands In continental crust, granitic magma produced Yellowstone National Park Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Mountains CHECK YOUR NEIGHBOR Mountains are generally formed

A. B. C. D. E. along convergent plate boundaries. by tectonic forces. where continents collide. where uplift results from crustal thickening. all of the above. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Mountains CHECK YOUR ANSWER Mountains are generally formed A. B. C. D. E. along convergent plate boundaries. by tectonic forces. where continents collide. where uplift results from crustal thickening.

all of the above. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Mountains CHECK YOUR NEIGHBOR Weathering and erosion wears mountains down, but many mountains continue to maintain their lofty stature because A. B. C. D. of isostatic convergence.

the rate of uplift counters the rate of erosion. magma pushes them upward at a faster rate than erosion wears them down. tensional forces in subduction zones continue to operate and push rock upward. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Mountains CHECK YOUR ANSWER Weathering and erosion wears mountains down, but many mountains continue to maintain their lofty stature because A. B.

C. D. of isostatic convergence. the rate of uplift counters the rate of erosion. magma pushes them upward at a faster rate than erosion wears them down. tensional forces in subduction zones continue to operate and push rock upward. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Mountains CHECK YOUR NEIGHBOR

Most of the worlds volcanoes are formed around the Ring of Fire because A. B. C. D. of seafloor spreading in the Pacific Plate. the Pacific Plate is surrounded by subduction zones and associated convergent boundaries. the Pacific Ocean floor is very thin, and magma plumes are very close to the surface. it burns, burns, burns. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Mountains CHECK YOUR ANSWER Most of the worlds volcanoes are formed around the Ring of Fire because A. B. C. D. of seafloor spreading in the Pacific Plate. the Pacific Plate is surrounded by subduction zones and associated convergent boundaries. the Pacific Ocean floor is very thin, and magma plumes are very

close to the surface. it burns, burns, burns. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Earths Waters Earth is 71% covered by water: ~97% is saltwater in the oceans; ~3% is fresh water. ~2% is frozen in ice caps and glaciers. ~1% is liquid fresh water in groundwater, and water in rivers, streams, and lakes. A small amount is water vapor. Earths waters are constantly circulating. The driving forces are:

Heat from the Sun Force of gravity Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Earths Waters The hydrologic cycle is the set of processes that controls the circulation of water on Earth. Processes involved in the hydrologic cycle: Evaporation

Precipitation Infiltration Runoff Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Earths Waters Water that goes from the ocean back to the ocean completes a hydrologic cycle. The journey is not always direct, and water can flow as: Streams, rivers, and groundwater Water can also be frozen in ice caps and glaciers

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Ocean Floor Ocean floor encompasses continental margins and deep ocean basins. Continental margins are between shorelines and deep ocean basins. Continental shelfshallow; underwater extension of the continent. Continental slopemarks boundary between continental and oceanic crust. Continental risewedge of accumulated sediment at base of continental slope. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

The Ocean Floor The ocean bottom is not flat, it is etched with deep canyons, trenches, crevasses. Underwater mountains rise upward from the seafloor. The deep-ocean basin: Basalt from seafloor spreading plus thick accumulations of sediment Abyssal plains, ocean trenches, and seamounts Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Ocean Floor The deep-ocean basin:

Abyssal plainsflattest part of the ocean floor due to accumulated sediment Ocean trencheslong, deep, steep troughs at subduction zones Seamountselevated seafloor from volcanism Mid-ocean ridges: Sites of seafloor spreading (volcanic and tectonic activity) A global mid-ocean ridge system winds all around the Earth Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Ocean Floor The deepest parts of the ocean are at the

ocean trenches near some of the continents. The shallowest waters are in the middle of the oceans around underwater mountains (mid-ocean ridge system). Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Ocean CHECK YOUR NEIGHBOR Ocean trenches are the deepest parts of the ocean floor because A. B.

C. D. that is where oceanic crust meets continental crust. that is where subduction occurs. no sediment accumulates in trenches. all accumulated sediment settles in the abyssal plain. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Ocean CHECK YOUR ANSWER Ocean trenches are the deepest parts of the ocean floor because

A. B. C. D. that is where oceanic crust meets continental crust. that is where subduction occurs. no sediment accumulates in trenches. all accumulated sediment settles in the abyssal plain. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Waves Characteristics of waveswaves get their energy from the wind.

The crest is the peak of the wave. The trough is the low area between waves. Wave height is the distance between a trough and a crest. Wavelength is the horizontal distance between crests. Wave period is the time interval between the passage of two successive crests. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Waves Height, length, and period of a wave depend on: Wind speed

Length of time wind has blown Fetchthe distance that the wind has traveled across open water Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Waves Wave of oscillation: Wave energy moves forward, not water Occurs in the open sea in deep water Wave of translation: Shallow water; depth about one-half wavelengthwave begins to feel bottom Wave grows higher as it slows and wavelength shortens

Steep wave front collapses, wave breaks Turbulent water goes up the shore and forms surf Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Waves CHECK YOUR NEIGHBOR When a wave approaches the shore, the water depth decreases. This affects the wave by flattening its circular motion, A. B. C. D.

decreasing its speed, and increasing distance between waves and wave height. increasing its speed and distance between waves, and decreasing wave period. decreasing its speed and distance between waves, causing wave height to increase. increasing its speed and distance between waves, causing wave height to increase. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Waves CHECK YOUR ANSWER When a wave approaches the shore, the water depth decreases. This affects the wave by flattening its circular

motion, A. B. C. D. decreasing its speed, and increasing distance between waves and wave height. increasing its speed and distance between waves, and decreasing wave period. decreasing its speed and distance between waves, causing wave height to increase. increasing its speed and distance between waves, causing wave height to increase.

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Water Ocean water is a complex solution of mineral salts, dissolved gases, and decomposed biological material. Salinity: the proportion of salts to pure water. ~35 grams salts per 1000 grams of water Salinity and temperature control density Salty, cold water is denser than less salty, warmer water Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Ocean Water Salinity is variable: Salinity decreases as fresh water enters the ocean: Runoff from streams and rivers Precipitation Melting of glacial ice Salinity increases as fresh water leaves the ocean: Evaporation Formation of sea ice Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Water

CHECK YOUR NEIGHBOR The density of seawater is controlled by A. B. C. D. salinity. temperature and salinity. pressure and salinity. sea ice and runoff. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Ocean Water CHECK YOUR ANSWER The density of seawater is controlled by A. B. C. D. salinity. temperature and salinity. pressure and salinity. sea ice and runoff.

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Water CHECK YOUR NEIGHBOR The salinity and, hence, density of seawater increase by A. B. C. D. evaporation and precipitation. evaporation and formation of ice.

evaporation, runoff, and melting of sea ice. runoff, precipitation, and melting of glacial ice. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Ocean Water CHECK YOUR ANSWER The salinity and, hence, density of seawater increase by A. B. C. D.

evaporation and precipitation. evaporation and formation of ice. evaporation, runoff, and melting of sea ice. runoff, precipitation, and melting of glacial ice. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Earths Fresh Water Only ~3% of Earths water is fresh. Of the 3%, ~85% is frozen in ice sheets and glaciers ~14% is groundwater ~0.8% is in lakes and reservoirs, soil moisture, and rivers ~0.04% is water vapor

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Surface Water Surface water includes streams, rivers, lakes, and reservoirs. Infiltration of water is controlled by: Intensity and duration of precipitation Prior wetness condition of the soil Soil type

Slope of the land Nature of the vegetative cover Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Surface Water The land area that contributes water to a stream is called the drainage basin. Drainage basins are separated by drainage divides. The largest drainage divides are continental divides. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Groundwater Water beneath the ground exists as groundwater and soil moisture. Groundwater occurs in the saturated zone water has filled all pore spaces. Soil moisture is above the saturated zone in the unsaturated zonepores filled with water and air. The water table is the boundary between these two zones. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Groundwater The depth of the water table varies with

precipitation and climate. Zero in marshes and swamps, hundreds of meters in some deserts. At perennial lakes and streams, the water table is above the land surface. The water table tends to rise and fall with the surface topography. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Groundwater Factors that influence storage and movement of groundwater: Porosity: ratio of open space in soil, sediment, or rock to total volume of solids plus voids

the amount of open space underground. Greater porosity equals more potential to store greater amounts of groundwater. Particle size, shape, and sorting influence porosity. Soil with rounded particles of similar size has higher porosity than soil with various sizes. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Groundwater Permeability Degree to which groundwater can flow through a porous materialhigher permeability, greater potential for fluid flow. Sediment packing and connectedness of

pores influences permeabilityexample of clay and sandstone: Both have high porosity, but clays small, flattened sediment grains makes for tighter packing and smaller pores. Water cannot flow easily through small pores so clay has low permeability. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Groundwater CHECK YOUR NEIGHBOR A soil with rounded particles of similar size will have a higher porosity than a soil with rounded particles of various sizes, because A. B.

C. D. it will have a higher permeability. water flows more easily through rounded particles. smaller sediment grains will fill the open pore spaces between larger grains. poorly sorted sediment will have more open pore spaces. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Groundwater CHECK YOUR ANSWER A soil with rounded particles of similar size will have a higher porosity than a soil with rounded particles of various

sizes, because A. B. C. D. it will have a higher permeability. water flows more easily through rounded particles. smaller sediment grains will fill the open pore spaces between larger grains. poorly sorted sediment will have more open pore spaces. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Groundwater

Aquifers are reservoirs of groundwater. Aquifers generally have high porosity and high permeability. Aquifers underlie the land surface in many areas; they are a vital source of fresh water. It is important to keep this vital source of fresh water clean and contaminant free. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Surface Processes Earths surface is worn away by the processes of erosion. Agents of erosion include:

Gravity Water Wind Ice Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Gravity Mass movementthe downslope movement of Earth material (rock, soil, debris, land), due to gravity.

Rapid movement: Debris avalanche, rock fall, rock slide, landslide, debris flow Evidence: concave scars, debris, buried structures Slow movement: Soil creep, rock slump Evidence: broken retaining walls, bent tree trunks Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Surface Water Running water shapes Earths surface in two opposing ways: fast water transports sediment, slow water deposits sediment.

Streamflowtwo types of flow; stream speed Laminar flowslow and gentle Turbulent flowfast and rapid Factors that determine velocity: Gradient, or slope Channel characteristics (shape and size) Dischargevolume of water moving past a given point in a certain amount of time Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Surface Water Stream erosion: Loosely consolidated particles are lifted by abrasion and dissolution.

Stronger currents lift particles more effectively: Stronger currents have higher energy Lift and transport more and bigger particles Turbulent versus laminar flow Downward limit to stream erosion: The lowest point to which a stream can erode is called base level. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Surface Water Two general types of base level:

Ultimate (sea level) Local or temporary (lake, etc.) Raising base level causes deposition Lowering base level causes erosion Transportation of sediment by streams: Capacity: maximum load a stream can transport controlled by stream discharge Competence: maximum particle size a stream can transport controlled by stream velocity

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Surface Water Decreased velocity causes sediment deposition competence and capacity reduced, sediment drops out of flow. Stream sediments (alluvium) are generally well sorted. Natural leveesform parallel to stream channel by successive floods Alluvial fans develop where a high-gradient stream abruptly leaves a narrow valley Deltas form when stream enters an ocean, bay, or lakecreates new land Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

The Work of Surface Water CHECK YOUR NEIGHBOR As a river flows down to lower elevations, stream velocity A. B. C. D. increases, capacity and competence decrease. decreases, causing capacity and competence to decrease. decreases, and capacity and competence increase. increases as it forms a delta.

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Surface Water CHECK YOUR ANSWER As a river flows down to lower elevations, stream velocity A. B. C. D. increases, capacity and competence decrease. decreases, causing capacity and competence to decrease.

decreases, and capacity and competence increase. increases as it forms a delta. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Groundwater Flowing groundwater can alter and change features at the surface: Land subsidence Caves and caverns Sinkholes Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Groundwater

Land Subsidence: Extreme groundwater withdrawal by pumping from wells can result in lowering of the landland subsidence. Land subsidence is especially prevalent in aquifers made of sandy sediments and interbedded clays. The clays leak water to the sand, then when water is pumped out, the clays shrink and compact, causing subsidence. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Groundwater

Caverns and caves The dissolving action of groundwater eats away at rocklimestone in particular. Rainwater chemically reacts with CO2 in the air and soil, producing carbonic acid. The acidified water seeps into rock (especially limestone), partially dissolving it. Such action has carved out magnificent caves and caverns (a cavern is a large cave). Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Groundwater Sinkholes are funnel-shaped cavities in

the ground that are open to the sky; they are formed similar to caves. They can also be formed from conditions of drought and the over withdrawal of groundwater. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Wind Wind blows everywhere, but its impact on sculpting the land is minor. Impact is greatest where: Strong winds blow frequently Vegetation is sparse or absent Plant roots keep particles together

Plants deflect wind and shelter particles Surface particles are small Small particles are more easily lifted and transported Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Glaciers Glaciers are powerful agents of erosion. A glacier is like a plow as it scrapes and plucks up rock and sediment. Glaciers are also powerful agents of deposition. A glacier is like a sled as it carries its heavy load to distant places.

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Glaciers A glacier is an accumulation of snow and ice thick enough to move under its own weight. Two types of glaciers: Alpine Continental Alpine glaciers develop in mountainous areas, generally confined to individual valleys. Cascades, Rockies, Andes, Alps, Himalayas Erosional landforms: cirque, arte, horn, hanging valley, U-shaped valley

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Work of Glaciers Continental Glaciers: Spread over large areas Antarctica, Greenland, Alaska Erosional landforms Roches moutonees, striations Depositional landforms Moraine, kame, esker, drumlin Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Surface Processes CHECK YOUR NEIGHBOR

There are many erosive agents that sculpt Earths surface. Overall, the erosive agent that does the most work is A. B. C. D. wind. groundwater. running water. glaciers. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

Surface Processes CHECK YOUR ANSWER There are many erosive agents that sculpt Earths surface. Overall, the erosive agent that does the most work is A. B. C. D. wind. groundwater. running water. glaciers.

Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

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