hewitt/lyons/suchocki/yeh conceptual integrated science

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

Hewitt/Lyons/Suchocki/Yeh

Conceptual Integrated Science

Chapter 24EARTH’S SURFACE—

LAND AND WATER


This lecture will help you understand:

• A survey of Earth’s landforms• Folds and faults and how they are

classified• The different types of mountains• The topography of the ocean floor• Earth’s water and where it is found• The different erosive agents that sculpt

Earth’s surface


Earth’s 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)


Earth’s Many LandformsEarth 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.


Earth’s Many LandformsContinental 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


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.


Crustal Deformation

Compressional stress—convergent plate boundary• Pushing together of rock masses

Tensional stress—divergent plate boundary• Pulling apart of rock masses

Shear stress—transform fault-plate boundary• Rock masses sliding past one another


Crustal DeformationElastic deformation• Size and shape deform, but rock returns to

original form when stress is removedFracture• Elastic limit of rock exceeded; rock breaks• Colder, surface rock

Plastic deformation• Elastic limit of rock exceeded; shape

changed permanently—folds• Warmer, subsurface rock


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.


Folds• Anticlines—upfolded or arch-shaped rock

layers.• Oldest rock layers at the fold core, rock layers get

younger away from core.• Synclines—downfolds or trough-shaped rock

layers.• Youngest rocks at the fold core, rock layers get

older away from the core.


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


Dip-Slip FaultsDip-slip fault movement is up or down• Footwall—rock below the fault surface

where a miner could stand. • Hanging wall—rock above the fault surface

where a miner could hang a lamp.

Normal fault: hanging wall moves down relative to footwall—tension

Reverse fault: hanging wall moves up relative to footwall—compression


Dip-Slip Faults


Strike-Slip FaultsDisplacement 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)


Strike-Slip FaultsTransform fault-plate boundary:• Large strike-slip fault that cuts through

the lithosphere, accommodates motion between two tectonic plates

• San Andreas Fault zone—major transform fault separating Pacific Plate and North American Plate


Strike-Slip Faults


Oblique-Slip FaultsFaults 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.


Rocks begin to deform when they

A. become subjected to folding and faulting.B. are subjected to compressional, tensional, or shear forces.C. break.D. undergo partial melting.

Crustal DeformationCHECK YOUR NEIGHBOR


Rocks begin to deform when they

A. become subjected to folding and faulting.B. are subjected to compressional, tensional, or shear forces.C. break.D. undergo partial melting.

Crustal DeformationCHECK YOUR ANSWER


Rocks deform and fold in response to

A. tensional forces that elongate the crust.B. tensional forces that shorten the crust.C. compressional forces that elongate the crust.D. compressional forces that shorten the crust.



A normal fault is created as rock in the hanging wall

A. drops down relative to rocks in the footwall. Tension pulls the rock apart.

B. drops down relative to rocks in the footwall. Tension pushes the rock together.

C. moves up relative to rocks in the footwall. Compression pulls the rock apart.

D. moves up relative to rocks in the footwall. Compression pushes the rock together.



A normal fault is created as rock in the hanging wall







A reverse fault is created as rock in the hanging wall







MountainsMountains 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


Folded MountainsMountains mostly occur at convergent

plate boundaries—crustal thickening causes uplift.

• Compression folds, thickens, and shortens the crust—isostatic uplift

Continental collision creates highest mountains

• Himalayas—India and Eurasia• Appalachians—North America and

Africa


Upwarped MountainsBroad upwarping of deeper rock deforms

overlying sedimentary rock, producing roughly circular structures—domes.

• 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.


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.


Fault-Block MountainsNormal 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


Volcanic MountainsVolcanic 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

Vent—an opening connected to the magma chamber via a pipe


Volcanic MountainsShield 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


Volcanic MountainsComposite 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)


Volcanic Mountains

Most volcanoes form near plate boundaries where converging plates meet.

About 75% of the world’s volcanoes are found in the “Ring of Fire” that encircles the Pacific Ocean.


Volcanic MountainsHot spots—stationary, 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


Mountains are generally formed

A. along convergent plate boundaries. B. by tectonic forces. C. where continents collide. D. where uplift results from crustal thickening.E. all of the above.

MountainsCHECK YOUR NEIGHBOR


Mountains are generally formed

A. along convergent plate boundaries. B. by tectonic forces. C. where continents collide. D. where uplift results from crustal thickening.E. all of the above.

MountainsCHECK YOUR ANSWER


Weathering and erosion wears mountains down, but many mountains continue to maintain their lofty stature because

A. of isostatic convergence.B. the rate of uplift counters the rate of erosion.C. magma pushes them upward at a faster rate than erosion wears

them down.D. tensional forces in subduction zones continue to operate and

push rock upward.



Most of the world’s volcanoes are formed around the “Ring of Fire” because

A. of seafloor spreading in the Pacific Plate.B. the Pacific Plate is surrounded by subduction zones and

associated convergent boundaries. C. the Pacific Ocean floor is very thin, and magma plumes are very

close to the surface.D. it burns, burns, burns.



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.

Earth’s waters are constantly circulating. The driving forces are:

• Heat from the Sun • Force of gravity

Earth’s 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

Earth’s Waters


Earth’s 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


The Ocean FloorOcean floor encompasses continental

margins and deep ocean basins.Continental margins are between

shorelines and deep ocean basins. • Continental shelf—shallow; underwater

extension of the continent.• Continental slope—marks boundary

between continental and oceanic crust.• Continental rise—wedge of accumulated

sediment at base of continental slope.


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

The Ocean Floor


The deep-ocean basin:• Abyssal plains—flattest part of the ocean floor due

to accumulated sediment• Ocean trenches—long, deep, steep troughs at

subduction zones• Seamounts—elevated 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

The Ocean Floor


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).


Ocean trenches are the deepest parts of the ocean floor because

A. that is where oceanic crust meets continental crust. B. that is where subduction occurs.C. no sediment accumulates in trenches. D. all accumulated sediment settles in the abyssal plain.

The OceanCHECK YOUR NEIGHBOR


Ocean trenches are the deepest parts of the ocean floor because

A. that is where oceanic crust meets continental crust. B. that is where subduction occurs.C. no sediment accumulates in trenches. D. all accumulated sediment settles in the abyssal plain.

The OceanCHECK YOUR ANSWER


Ocean WavesCharacteristics of waves—waves 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.


Ocean WavesHeight, length, and period of a wave

depend on:• Wind speed• Length of time wind has blown• Fetch—the distance that the wind has

traveled across open water


Ocean WavesWave 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 wavelength—wave

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


When a wave approaches the shore, the water depth decreases. This affects the wave by flattening its circular motion,

A. decreasing its speed, and increasing distance between waves and wave height.

B. increasing its speed and distance between waves, and decreasing wave period.

C. decreasing its speed and distance between waves, causing wave height to increase.

D. increasing its speed and distance between waves, causing wave height to increase.

Ocean WavesCHECK YOUR NEIGHBOR


When a wave approaches the shore, the water depth decreases. This affects the wave by flattening its circular motion,

A. decreasing its speed, and increasing distance between waves and wave height.

B. increasing its speed and distance between waves, and decreasing wave period.

C. decreasing its speed and distance between waves, causing wave height to increase.

D. increasing its speed and distance between waves, causing wave height to increase.

Ocean WavesCHECK YOUR ANSWER


Ocean WaterOcean 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


Ocean WaterSalinity 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


The density of seawater is controlled by

A. salinity. B. temperature and salinity.C. pressure and salinity. D. sea ice and runoff.

Ocean WaterCHECK YOUR NEIGHBOR


The density of seawater is controlled by

A. salinity. B. temperature and salinity.C. pressure and salinity. D. sea ice and runoff.

Ocean WaterCHECK YOUR ANSWER


The salinity and, hence, density of seawater increase by

A. evaporation and precipitation.B. evaporation and formation of ice.C. evaporation, runoff, and melting of sea ice.D. runoff, precipitation, and melting of glacial ice.

Ocean WaterCHECK YOUR NEIGHBOR


The salinity and, hence, density of seawater increase by

A. evaporation and precipitation.B. evaporation and formation of ice.C. evaporation, runoff, and melting of sea ice.D. runoff, precipitation, and melting of glacial ice.

Ocean WaterCHECK YOUR ANSWER


Earth’s Fresh Water

Only ~3% of Earth’s 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


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


Surface WaterThe 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.


GroundwaterWater 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 zone—pores filled with water and air.

The water table is the boundary between these two zones.


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.


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.


GroundwaterPermeability• Degree to which groundwater can flow

through a porous material—higher permeability, greater potential for fluid flow.

• Sediment packing and connectedness of pores influences permeability—example of clay and sandstone:

— Both have high porosity, but clay’s small, flattened sediment grains makes for tighter packing and smaller pores. Water cannot flow easily through small pores— so clay has low permeability.


A soil with rounded particles of similar size will have a higher porosity than a soil with rounded particles of various sizes, because

A. it will have a higher permeability. B. water flows more easily through rounded particles. C. smaller sediment grains will fill the open pore spaces between

larger grains.D. poorly sorted sediment will have more open pore spaces.

GroundwaterCHECK 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. it will have a higher permeability. B. water flows more easily through rounded particles. C. smaller sediment grains will fill the open pore spaces

between larger grains.D. poorly sorted sediment will have more open pore spaces.

GroundwaterCHECK YOUR ANSWER


GroundwaterAquifers 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.


Surface Processes

• Earth’s surface is worn away by the processes of erosion.

• Agents of erosion include:• Gravity• Water• Wind• Ice


The Work of Gravity

Mass movement—the 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


The Work of Surface Water

Running water shapes Earth’s surface in two opposing ways: fast water transports sediment, slow water deposits sediment.

Streamflow—two types of flow; stream speed• Laminar flow—slow and gentle• Turbulent flow—fast and rapid

Factors that determine velocity:• Gradient, or slope• Channel characteristics (shape and size)• Discharge—volume of water moving past a given

point in a certain amount of time


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.


The Work of Surface WaterTwo 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


The Work of Surface WaterDecreased velocity causes sediment deposition

—competence and capacity reduced, sediment drops out of flow.

Stream sediments (alluvium) are generally well sorted.

• Natural levees—form 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 lake—creates new land


As a river flows down to lower elevations, stream velocity

A. increases, capacity and competence decrease.B. decreases, causing capacity and competence to decrease. C. decreases, and capacity and competence increase. D. increases as it forms a delta.

The Work of Surface WaterCHECK YOUR NEIGHBOR


As a river flows down to lower elevations, stream velocity

A. increases, capacity and competence decrease.B. decreases, causing capacity and competence to decrease. C. decreases, and capacity and competence increase. D. increases as it forms a delta.

The Work of Surface WaterCHECK YOUR ANSWER


The Work of Groundwater

Flowing groundwater can alter and change features at the surface:• Land subsidence• Caves and caverns• Sinkholes


The Work of GroundwaterLand Subsidence:• Extreme groundwater withdrawal

by pumping from wells can result in lowering of the land—land 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.


The Work of GroundwaterCaverns and caves• The dissolving action of groundwater “eats

away” at rock—limestone 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).


The Work of GroundwaterSinkholes 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.


The Work of WindWind 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


The Work of GlaciersGlaciers 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.


The Work of GlaciersA 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, arête, horn, hanging

valley, U-shaped valley


The Work of GlaciersContinental Glaciers:• Spread over large areas

—Antarctica, Greenland, Alaska

• Erosional landforms—Roches moutonees, striations

• Depositional landforms—Moraine, kame, esker, drumlin


There are many erosive agents that sculpt Earth’s surface. Overall, the erosive agent that does the most work is

A. wind. B. groundwater. C. running water.D. glaciers.

Surface ProcessesCHECK YOUR NEIGHBOR


There are many erosive agents that sculpt Earth’s surface. Overall, the erosive agent that does the most work is

A. wind. B. groundwater. C. running water.D. glaciers.

Surface ProcessesCHECK YOUR ANSWER

hewitt/lyons/suchocki/yeh conceptual integrated science

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