Geology 101 Test 3

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All water in,on, and around Earth; Includes water in atmosphere; underground, and above ground, water vapor, ice in glaciers/snow and surface/subsurface water in lakes and streams

Ground Water (Subsurface Water)

Sources: infiltration of water into Earth, rain, streams, ocean; from Earth's interior-some may be "original"; Character: Fresh, saline with variable amounts of dissolved materials.

Zone of Aeration (also called Vadose Zone)

Zone near Earth's surface where pores and openings in rocks are unfilled or partly filled with water; Subsurface water, but not "groundwater"; Also called soil moisture.

Zone of Saturation (Phreatic Zone)

Zone below the aerated zone in which all pores and openings are water-filled


Water in the Zone of saturation

Water Table

Boundary between zones of saturation and aeration

Water Table (characteristics)

Occurs only in unconfined aquifers; Surface usually not flat; usually undulates with the surface topography and with other factors; Distance below ground surface changes with rainfall amount


Rock or sediment with high porosity and permeability; Water withdrawal possible in large amount, quickly; Chiefly sandstones, unconsolidated sands and gravels; Limestones with interconnected solution channels and fractures.


Material with low permeability and very slow water movements; unweathered, unfractured igneous rock; Limestone without fractures, caves, or connected voids; Shales


Earth material with relatively low permeability and relatively slow water movement; Between aquifer and aquiclude in permeability; Ex. sandstone with pores partly filled with clay

Unconfined Aquifer;

an aquifer overlain by permeable earth materials; In well, water rises to top of water table;

Recharge from

ground surface directly above water table; other locations by lateral flow; water flows out without pumping only where WT (water table) intersects Earth's surface

Confined Aquifer

Aquifer bounded above and below by aquicludes/aquitards; Recharge only from lateral inflow of groundwater from other areas (recharge areas)

Perched Aquifer

Localized layer of impermeable material within an otherwise permeable material; Water temporarily trapped above this layer; Perched aquifers cannot usually sustain high well yields because of their limited extent

Artesian Well

Recharge area at higher elevation than top of confined aquifer water surface;Water will flow upward in well without pumping;If recharge area is higher than ground elevation where well is drilled, water may flow onto the ground without pumping

Artesian System

entire groundwater system associated with artesian conditions

Potentiometric Surface

elevation up to which water will move in artesian system well

Effects of people on groundwater resources: Reduction in Recharge Rate

Urbanization-reduces permeability of recharge areas; Destruction of vegetative cover-reduces infiltration

Effects of People Groundwater Resources: Loss of producing water wells by pumping

Cones of depression; Magnitude of effect-recharge rate/ withdrawal rate;

Withdrawal rate> recharge rate

cones become deeper, may overlap with other cones, may lower groundwater table over large area

Effects of People Groundwater Resources

If zone of saturation is lowered enough, aquifer may be essentially depleted in water; Permanent destruction of aquifer possible-subsidence; Major problem in Nebraska, west Texas and ajacent states (the Ogallala Aquifer System p. 242 of textbook); water loss may destroy irrigation farming in these areas.

High Plains/Ogallala Aquifer System

Developed over millions of years; covers 170,000 square miles; its 3.3 billion acre feet of fresh water would fill Lake Huron with enough water remaining to fill one-fifth of Lake Ontario; Responsible for over $20 billion per year in flood and fiber production

Effects if People on Groundwater Resources: Land Subsidence

Lowering of water table removes water from pores in sandstones and other aquifers; Loss of support of sand grains by water causes collapse into voids-sand becomes closer packed-> land subsidence; Pores permanently lost- aquifer destroyed forever

Subsidence (history)

Subsidence of 9 Meters (approx. 30 ft.) occurred between 1925 and 1977 in the San Joaquin Valley of California.

Types of Land Movement

Slides, Falls, And Flows


Downslope movement of material, no mixing; Material sliding along curved slip plane; Produces slump block


Material free-falls, as from a vertical face


Downslope movement in which material mixes

Forces on Slopes

Driving Forces, Resisting Forces, and Safety factor

Driving Forces

Weight of material; Offset of center of gravity due to slope angle

Resisting Forces

Strength of rock or soil; Length of surface along which slip occurs

Safety factor

Ratio of resisting factors to driving forces

Safety Factor for Slump

If most weight is at top center while center of gravity is at bottom center material will be off balance & more likely to fall

Rotational Slides (slump)

Typical for soil or unconsolidated sediment (not mixed together); Involves backward rotation of material;Commonly produces benches near top

Translational Slides

Typical for layered (bedded) rock or rock with large horizontal joints; Soil slides are a form of _____________ involving upper soil layers.

Slope Stability

Water can help stabilize or destabilize slopes; Surface tension of water in small amounts help hold soil particles together (will hold soil together, make it stronger); Too much water destabilizes slope (make it weaker); Deep infiltration of water can have delayed effect on slope stability; Erosion of base or toe can destabilize slope; Quick Clay. These are different ways of _______

Effect of Human Activity on Slope Stability

_______________is now recognized as the single greatest geologic agent; Affect slope stabilities in many ways; timber harvesting (effect is controversial); Urbanization, Built roads, move roads, move to areas with sleep slopes, add weight from homes, industries, remove vegetation

Vaiont Reservoir Slide (Vaiont Dam)

___________ was world's highest thin-arch dam, built in Italian Alps; Although the dam itself was well designed, it was poor sited; Local bedrock consisted of highly fractured and porous limestone and weak clay layers inclined toward reservoir; Water in reservoir increased water pressure in soil (caused dam to fail)

Identifying Potential Landslides

Avoiding future __________ requires identification of potential ___________ sites; Evidence previous _________; good indicator of potential future ___________; Hummocky surfaces; disrupted vegetation; thinner than normal soils;Must evaluate potential ___________- sites; _________ inventory map; very useful for risk evaluation and land use planning; Detailed site evaluation should still be before construction is allowed.

Preventing Landslides

Impossible to prevent large _________; can reduce risks of _________; Drainage Control; keep surface water from seeping into ground; install drainage tubes; Grading; reduce slopes or create benches; Slope Supports, retaining walls

Snow Avalanches

Mountainous areas at high elevations subject to Rapid downslope movement of snow, ice and other debris; typically occur at same locations (chutes) year after year; effort to trigger avalanches before they become dangerous; Avalanche hazard maps produced for some areas


Removal of subsurface support may cause sinking of ground; Removal of support may occur due to several reasons; dissolution of rocks (most commonly limestone or evaporites) to form sinkholes; Overpumping of water or other fluids; Abandoned underground mines

Coastal Hazards

30 of 50 US states boarder an ocean, gulf of Mexico, or one of the Great Lakes; Approximately 85% of U.S. population lives in these states; More people live in coastal counties than inland counties; About half of population in states with a coastline live near the coast

Active Margins

Coasts may be on edge of continent at a convergent plate boundary; Seismic activity causes land to rise or sink faster than wave action can modify it; forms features such as arches, stacks sea cliffs; terraces and wave-cut platforms

Passive Margins

May be on edge of continent far away from plate boundary; typically form wide beaches, barrier islands, deltas

tides and waves.

Major processes affecting coasts are

Spring Tides

Are larger than average tides; occur monthly as Moon revolves around Earth

Neap Tides

Are smaller than average tides; occur monthly as Moon revolves around Earth


Caused by wind; key measurements of waves are wavelength and wave height (amplitude); Energy is transmitted as wave, but water only moves in circular fashion; Circular motion of water decreases with depth;

Wave Base

is depth below which no motion occurs; wave base approx. equal to 1/2 wavelength


Forms when waves encounter sea floor at a depth less than the wave base; Waves begin to slow down as they reach shallower water; When piles up as wavelength as wavelength shortens; When water reaches a certain height, it "breaks", forming surf

Coastal Erosion: Sediment Transport

Waves rarely arrive perfectly parallel to a beach; Approach of waves at an angle to beach face means one end of wave will encounter shallow water before other end; Leads to wave refraction, or the bending of waves; creates the longshore current

Coastal Erosion: Sediment Transport (Longshore Current)

Moves sediment in a zig-zag pattern that, on average, is parallel to the beach;

Longshore Drift (Littorial Drift)

is the movement of sediment, a beach is therefore just a moving river of sand; must replenish sediment or starve beach

Coastal Erosion: Sediment Deprivation

Beaches can be deprived of sediment by several causes; Dam on rivers(rivers bring sediment) ; Structures built to hold sand in place (ex. Groins, breakwaters, Jetties); often create greater problem than existed originally.

Coastal Erosion: Headlands

Areas that protrude into sea more subject to erosion than areas farther back; Wave refraction concentrates energy on Headland areas; Effect is to straighten out shoreline

Coastal Erosion: Seacliffs

Seacliffs common on active coasts; may be caused by tectonic uplift or drop in sea level; Subject to both wave erosion and surface erosion

Beach Nourishment

Sand budget on many beaches is negative; Causes often human-related; US Army Corps of Engineers and other government replenish beaches with sand; some success; some failure; much controversy

Coastal Erosion: Storms

Waves are product of wind; Storms produce strong winds, therefore produce very large waves; Coastal erosion more severe during storms than at other times; Normal seasonal storms shift sediment from beach to off-shore storage, then back again onto beach

Coastal Erosions: Storms (2)

Major storms (hurricanes) produce far more erosion;

Storm Surge

Water is lifted up by low pressure in the eye of the storm; Strong winds push large waves; Barrier Islands particularly susceptible because of overwash

Coastal Management: E-Lines and E-Zones

Represent an attempt to control development in coastal areas; E refers to erosion; E values based on study of history of coastal erosion of a region and prediction of future erosion

Drainage Control

It keeps surface water from seeping into ground; install drainage tubes;

Control surface drainage, install pipes to enhance subsurface drainage, reduce the slope or create retaining walls

What can be used to reduce the risk of a landslide?

decreasing the recharge area by covering it with buildings, streets, and parking lots; reducing infiltration rates by removing vegetation

Urbanization can affect groundwater by....

Movement of largely unconsolidated material involving a backward rotation of the failed rock.

What is a correct description of a slump?

Water Table

The boundary separating the zone of aeration from the zone of saturation is called the

Agriculture, especially crop irrigation

The Principle Cause of depletion of water in the Great Plains Aquifer has been the use of water for

the depth to the bottom of the seafloor is less than the wavelength of incoming waves

Waves "break" to form surf when


True or False? Structures built along coastlines to hold sediment in place create a situation of sediment deprivation elsewhere, and may lead to greater problems than the one they were originally intended to solve.

When the Moon, Earth, and Sun are Aligned.

The phenomenon known as a "Spring Tide" occurs


True or False? The Water Table is a fixed, permanent feature that does not change within a human lifetime


True or False? The landslides described in the video "L" , the landslide in Wales could have been prevented, but the one in California was not preventable.


The largest source of usable fresh water is in

Cone of depression

Overpumping of groundwater from a region can lead to


True or False? An Aquifer in which there is an impermeable layer restricting the upper surface of the zone of saturation is called a confined aquifer.

high porocity and high permeability

To be considered a good aquifer, a body of earth material must have


True or False? Erosion is a significant problem along the Atlantic and Gulf coasts but insignificant in the Great Lakes region.

Cone of depression

Over pumping of a well produces a(n) ___________ on the surface of the water table.

The ratio of resisting forces to driving forces

Slope stability is evaluated by computing a safety factor (SF). What is the definition of the safety factor (SF)

Storm surges, high winds, and heavy rainfall that cause flooding

Damage from hurricanes is caused by


When waves enter water that is shallower than their wave base, they form


What type of bedrock is most likely to contribute to creep, earthflows, slumps, and soil slips?


The percentage of lakes and ponds in Iowa that have been found to exist in a eutrophic state is

Local erosion will decrease but overall erosion will accelerate

What is likely to result from the installation of engineered erosion control structures?


Movement of surface water into rocks or soil is called


A type of downslope movement characterized by slow flowing, sliding, or slipping, or slipping of soil and other earth materials is called


True or False? An aquifer in which there is no impermeable layer restricting the upper surface of the zone of saturation is called a confined aquifer


The ability of a material to transmit water or other fluids is called


The largest source of usable fresh water is

Dam Collaspe did NOT contribute to the disaster

Landslides can cause large human disasters, such as the Vaiont Dam disaster on October 9, 1963 in Italy; What did NOT contribute to the disaster?

weak rocks, increased pore pressure, heay rainfall preceding landslide

the Vaiont Dam disaster on October 9, 1963 in Italy; What DID contribute to the disaster?

Barrier Islands

What is indicative of a passive coastal margin?

Saltwater Intrusion

Where Overpumping of groundwater occurs in coastal areas, __________ may occur


True of False? The best way to stabilize a slope is to hold it in place by building a home or other large structure on the top of the slope

Areas with thinner than normal soil, as compared to surrounding areas, areas with irregular, hummocky surfaces

What is indicative of an area prone to landslides?

the bending of waves as they approach the coast at an angle

The longshore current is caused by

gentle slope with soil having a high shear strength

What area would be considered least likely to experience a landslide?

Two high tides and Two low tides

In a period of slightly less than 25 hours, a location along a coastline will experience


are often constructed in pairs at the mouth of a river or inlet, they stabilize the channel, prevent or minimize deposition of sediment in the channel and generally protect it from large waves.


Are linear structures placed perpendicular to the shore, designed to trap a portion of the sand that moves in the littoral transport system.


protect limited stretches of shoreline from waves, designed to intercept waves and provide a protected area, or harbor, for boat mooring


are structures constructed parallel to the coastline to help retard erosion, may be of concrete, large stones, or wood, or other materials.

Tropical Cyclone

Severe storm generated from a tropical disturbance; called typhoons in most of the Pacific Ocean and Hurricanes in the Western Hemisphere.

Hydrologic Cycle (Water Cycle)

Circulation of water from the oceans to the atmosphere and back to the oceans by way of precipitation, evaporation, runoff from streams and rivers, and groundwater flow.

Drainage Basin

is an area of land that contributes water to a particular stream or river

Vadose Zone

Zone or layer above the water table in which some water may be suspended or moving in a downward migration toward the water table or laterally toward a discharge point.


Earth material capable of supplying groundwater at a useful rate from a well is called a(n)


Surface depression formed by a solution of limestone or collapse over a subterranean void such as a cave

Soil Slip

A type of mass wasting event that generally is narrow relative to width and is linear in form, develops during precipitation events on steep slopes;

Offstream use

is water that is removed or diverted form its source.


Engineering processes and technology that reduce salinity of water to such a level that it may be consumed by people or used in agriculture.

Consumptive use

is a type of offstream use in which water does not return to the stream or groundwater resource immediately after use.

Instream use

the water that is used is not withdrawn from its source; ex. water used to generate hydroelectric power.


is a landform consisting of loose material, such as sand or gravel, that has accumulated by wave action at the shoreline.

Beach budget

Inventory of sources and losses of sediment to a particular stretch of coastline

Beach Nourishment

Artificial processes of adding sediment (sand) to a beach for recreational and aesthetic purposes as well as to provide a buffer to coastal erosion

Rip current

A seaward flow of water in a confined narrow zone from a beach to beyond the breaker zone.


Steep (commonly near-vertical) bluff adjacent to and adjoining a beach or coastal environment; produced by a combination of erosional processes including wave activity and subaerial processes such as weathering, landsliding, and runoff of surface water from the land.

Mass Wasting

A comprehensive term for any type of downslope movement of earth materials.

Water Management

Practice of managing our water resources.


Landscape features such as swamps, marshes, bogs, or prairie potholes that are frequently or continuously inundated by water

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