Geology Exam #4

What are some of the effects of excessive groundwater withdrawal?

- Drying up of lakes and streams - Killing off vegetation (thus creating mass wasting) - Ground subsidence (San Joaquin dropped 30 ft in 52 years)

What are the different mass wasting events and how do they differ?

Landslides, creeps, slumps, rock avalanche, debris avalanche, mudflows, and rock falls

1000 atoms of a radioactive parent atom decays but contains 250 atoms. It's 1/2 life is 1 million. How old is the rock?

2 million years old

75% U235 and 25% Pb207. The half life is 4.5 billion years. How old is the rock?

2.25 billion years

12.5% K40 and 87.5% Ar40. Half life for the reaction of K40 to decay to Ar40 is 1.25 billion years old. How old is the rock?

3.75 billion years

What is an 'artesian well'?

A confined aquifer containing groundwater under high pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached.

Which is least likely to result in mass movement?

A slope with abundant vegetation

What is the angle of repose? What are the different factors which control this angle?

Angle of Repose: Maximum slope that loose, unconsolidated material can have - Depends on the size of particles, shape of particles, and water competent

What is karst topography?

Any region where the terrain has been dissolved by the physical and chemical weathering of the bedrock.

What is an aquifer? An aquiclude? An aquitard?

Aquifer: A material that is both porous and permeable Aquiclude: A material that is nonporous and/or impermeable Aquitard: Doesn't stop the fluid from passing through, just slows it down

How is water withdrawn from the subsurface?

By drilling up a well and pumping the water out: - Water in well, rises to the top of the water table - Water beneath the surface moves slowly (a few cm/m per day) depending on permeability - If water is extracted too fast, the water table will drop locally around the well called the "cone of depression"

How do geologists classify mass movements?

By the SPEED of the movement, the NATURE of the movement and the NATURE of the material.

How does a confined aquifer differ from an unconfined aquifer?

Confined aquifer: In the middle of lesser permeable rock or clay, and can build up additional pressure. When the pressure they build up exceeds the ground elevation, they are considered artesian and water will flow without pumping (as in a spring) at the grounds surface. Unconfined aquifer: Extend from the water table to the base of the aquifer, represented by an impermeable boundary. Most of the unconfined aquifers are formed by highly permeable layers (gravel, coarse or medium sand) and less permeable formations (silt or clay)

What is a creep? A flow?

Creep: Very slow, downhill movement of soil (1 cm/year); when tree trunks are tilted Flow: When motion is taking place within a moving mass of unconsolidated material

The term half life represents the time it takes for..

For half of the parent atoms to decay into daughter atoms.

What is the most important issue facing us today?

Groundwater (or lack thereof)

What is the major consumer of groundwater?

Irrigation

What are losing streams and gaining streams?

Losing streams: It "loses" water to the saturated zone. Also called the "influent stream". Gaining streams: It "gains" water from the saturated zone. The water table emerges above the ground along a gaining stream. Also called the "effluent stream".

The process by which masses of rock and soil move downhill under the influence of gravity is ______________.

Mass wasting

What is a parent isotope? A daughter?

Parent Isotope: An isotope that undergoes decay to form a daughter isotope Daughter Isotope: May be stable or may decay to form another daughter (formed from the parent isotope)

What is porosity? Permeability?

Porosity: Percentage of rock/sediment that consists of voids and openings Permeability: Ability of rock/sediment to allow a fluid to pass through it

What's groundwater?

Precipitation that enters the subsurface through infiltration

How is groundwater contaminated?

Road salt, toxic substances from mining sites, and used motor oil

Does groundwater move fast or slow? In what direction does it move?

Slow; downhill

_______________ only occurs in permafrost regions. a. Landsliding b. Soil creep c. Liquefaction d. Solifluction

Solifluction

How are the different mass wasting events subdivided?

Subdivided by the type of motion, type of material, and speed of motion

What are the possible triggers of mass wasting events?

The angle of repose (due to gravity) and "stupid human tricks"

How do caves form?

The dissolution of limestone. Rainwater picks up carbon dioxide from the air and as it percolates through the soil, which turns into a weak acid. This slowly dissolves out the limestone along the joints, bedding planes and fractures, some of which become enlarged enough to form caves. - Dissolved by the physical/chemical weathering of bedrock (a.k.a karst topography)

What is meant by mass wasting?

The general term for all gravity induced movement of material down a slope.

What is a half‐life?

The time required for 1/2 of a radioactive isotope to decay ion a stable daughter isotope

How does water enter into the subsurface?

Through the process of infiltration which is dependent on porosity and permeability

Loose, uncemented geologic material is said to be:

Unconsolidated

How is water distributed on the planet?

Water is distributed in freshwater and saltwater - 95.96% is in the ocean - 4.04% is fresh water

What is the water table? The vadose zone? The phreatic zone? The capillary fringe?

Water table: The level below which the ground is saturated with water Vadose zone: The unsaturated zone right beneath the ground Phreatic zone: The saturated zone underneath the water table The capillary fringe: The zone of soil immediately above the water table

What is a 'perched' water table?

When the water table reaches the Earth's surface

How do springs form?

Where the aquifer surface meets the ground surface.

How fast is soil creep? a. 1 to 10 millimeters per year b. 1 to 10 meters per year c. 1 kilometers per hour d. over 10 kilometers per hour

a. 1 to 10 millimeters per year

An igneous rock was formed with 8000 radioactive (parent) atoms but contains only 1000 radioactive (parent) atoms today. If the half-life for the radioactive element is 10 million years, the rock is ___ million years old. a. 30 b. 70 c. 80 d. 10

a. 30

What slope is least stable? a. A slope where the sedimentary layers dip parallel to the slope b. A slope where the sedimentary layers dip perpendicular to the slope c. A slope where the sedimentary layers are coarse d. A slope where the sedimentary layers have large roots in them

a. A slope where the sedimentary layers dip parallel to the slope

Who first discovered radioactivity? a. Henri Becquerel b. Charles Darwin c. Ernest Rutherford d. Marie Curie

a. Henri Becquerel

If there are large particles, then there is _____ porosity. a. More b. Less c. The same d. None of the above

a. More

What is the era of geologic time that refers to "ancient life"? a. Paleozoic b. Mesozoic c. Cenozoic d. None of the above

a. Paleozoic

Difference between saturated and unsaturated zone: a. Pore spaces in saturated zones are full and pore spaces in unsaturated zones are not full b. Pore spaces in saturated zones are not full and pore spaces in unsaturated zones are full c. Pore spaces are very closed off depending on the water table d. Both have the same amount of pore space depending on the rock permeability

a. Pore spaces in saturated zones are full and pore spaces in unsaturated zones are not full

California imports most of its water supply. What is most (>80%) of the water used for? a. agriculture b. domestic irrigation (lawns) c. industry d. municipal drinking water

a. agriculture

Hadean is a geologic: a. eon b. era c. period d. epoch

a. eon

Which of the following are the largest divisions of geologic time? a. eons b. epochs c. eras d. periods

a. eons

How much of the Earth's total water is stored in underground aquifers? a. less than 1% b. about 5% c. about 20% d. about 50%

a. less than 1%

The process that breaks rocks into smaller pieces that are not changed in composition: a. physical weathering. b. chemical weathering. c. erosion. d. deposition.

a. physical weathering

Permeability is ______________. a. the ability of a solid to allow fluids to pass through b. the process by which plants release water vapor to the atmosphere c. the amount of water vapor in the air relative to the maximum amount of water vapor the air can hold d. the percentage of pore space in the rock

a. the ability of a solid to allow fluids to pass through

The boundary between the saturated zone and the unsaturated zone is called the ______________. a. water table b. aquifer c. aquiclude d. porosity

a. water table

In Western Europe, when the study of Earth's age began, most people believed Earth was about ________________ years old. a. 600 b. 6,000 c. 6,000,000 d. 4.6 billion

b. 6,000

Our Earth is ____ saltwater, and ____ freshwater. a. 75%; 25% b. 96%; 4% c. 99%; 1% d. 70%; 20%

b. 96%; 4%

Which is true? a. Coarse sand form steeper slopes that fine grain sand b. Angular pebbles form steeper slopes than coarse sand c. Round debris form steeper slopes than angular pebbles d. Fine grain sand form steeper slopes than coarse sand

b. Angular pebbles form steeper slopes than coarse sand

Adjacent to a pumping well, the water table is: a. Confined b. Depressed c. High d. Unconfined

b. Depressed

Dinosaurs lived during which era of geologic time? a. Paleozoic b. Mesozoic c. Cenozoic d. Precambrian

b. Mesozoic

What is the name of the scientist whose work laid the foundation for the modern science of stratigraphy? a. Henri Becquerel b. Nicolaus Steno c. Charles Darwin d. Alfred Wegener

b. Nicolaus Steno

If dinosaurs became extinct at the end of the Mesozoic, could they ever have coexisted with humans? a. Yes; extinction means the first appearance of an animal type. b. No; humans first evolved in the Cenozoic, long after the extinction (disappearance) of dinosaurs. c. There was no Mesozoic. Dinosaurs and humans were created at the same time as all animals—6,000 years ago. d. No; because humans first appeared in the Paleozoic.

b. No; humans first evolved in the Cenozoic, long after the extinction (disappearance) of dinosaurs.

Which of the following statements about the water table is false? a. The water table changes when discharge is not balanced by recharge b. The water table is generally flat c. The water table is above the land surface in lakes d. The water table is depressed near high volume pumping wells

b. The water table is generally flat

A nonconformity is: a. a rock unit that is different than the units above or below it. b. a gap in the geologic record bounded below by metamorphic or igneous rocks and bounded above by sedimentary rocks. c. a rock unit that does not contain fossils. d. the intrusive contact between igneous and sedimentary rocks

b. a gap in the geologic record bounded below by metamorphic or igneous rocks and bounded above by sedimentary rocks.

Archean is an eon that comes: a. before Proterozoic and after Phanerozoic. b. after Hadean and before Proterozoic. c. after Proterozoic and before Phanerozoic. d. after Phanerozoic and before Hadean.

b. after Hadean and before Proterozoic.

The unconformity along which tilted older sedimentary beds have been eroded off before deposition of horizontal sedimentary beds is called: a. disconformity b. angular unconformity c. nonconformity d. none of the above

b. angular unconformity

The lowering of the water table near a well is called a(n) ______________. a. aquiclude b. cone of depression c. influent zone d. sinkhole

b. cone of depression

Which of the following movements is the fastest? a. mudflow b. debris avalanche c. soil creep d. earthflow

b. debris avalanche

What is the process by which water enters the small pore spaces between particles of soil or rock? a. transpiration b. infiltration c. precipitation d. sublimation

b. infiltration

The concept that sedimentary beds in an outcrop contain fossils in a definite sequence is the: a. principle of superposition. b. principle of faunal succession. c. stratigraphic succession. d. principle of original horizontality.

b. principle of faunal succession.

The concept that sediments are deposited under the influence of gravity as approximately horizontal layers of particles is the: a. principle of faunal succession. b. principle of original horizontality. c. principle of superposition. d. stratigraphic succession.

b. principle of original horizontality.

What scientific avenue of investigation gave scientists the best estimate of the absolute age of the Earth? a. paleontological dating b. radiometric or isotopic dating c. carbon dating d. time it took to cool from molten ball

b. radiometric or isotopic dating

Solifluction may occur when ___________. a. the surface soil freezes while the deeper soil remains unfrozen b. the surface soil layer thaws while the deeper soil remains frozen c. the surface soil layer and the deeper soil both freeze d. the surface soil layer and the deeper soil both thaw

b. the surface soil layer thaws while the deeper soil remains frozen

The concept of half-life with respect to geologic time refers to: a. half of the time it takes for all of a radioactive element to break down. b. the time it takes for half of a parent isotope to change to the daughter isotope. c. the time it has taken for half of living organisms to become extinct. d. half of the time that there has been life on Earth.

b. the time it takes for half of a parent isotope to change to the daughter isotope.

What of the following was not a contributing factor in the 1925 Gros Ventre slide near Jackson Hole, Wyoming? a. the orientation of the sedimentary layers with respect to the slope b. undercutting of the slope by construction activities c. heavy rains and melting snow d. all of these were contributing factors

b. undercutting of the slope by construction activities

Approximately how many people die in the U.S. each year as a result of landslides? a. usually none b. 1 to 10 c. 25 to 50 d. more than 100

c. 25 to 50

Which has the steepest angle of repose? a. A hill with abundant vegetation b. A hill saturated in water c. A hill will damp sand d. A hill with angular pebbles

c. A hill will damp sand

A relatively impermeable geologic unit is called a: a. Aquifer b. Aquitard c. Aquiclude d. Confined aquifer

c. Aquiclude

Homo sapiens first appear during which geologic era? a. Paleozoic b. Mesozoic c. Cenozoic d. None of the above

c. Cenozoic

Which of the following sequences is written correctly from oldest to youngest? a. Cenozoic, Paleozoic, Mesozoic b. Mesozoic, Cenozoic, Paleozoic c. Paleozoic, Mesozoic, Cenozoic d. Paleozoic, Cenozoic, Mesozoic

c. Paleozoic, Mesozoic, Cenozoic

During which eon did multicellular algae and animals first appear in the fossil record? a. Archean b. Phanerozoic c. Proterozoic d. Hadean

c. Proterozoic

Which is NOT an important factor in causing mass movements? a. Shape of particle b. Size of particle c. Temperature of particle d. Water competent

c. Temperature of particle

What is the difference between the saturated and unsaturated zones of groundwater? a. The saturated zone has a higher porosity than the unsaturated zone b. The saturated zone has a lower porosity than the unsaturated zone c. The pore spaces in the saturated zone are completely full of water; the pore spaces in the unsaturated zone are not completely full of water d. The pore spaces in the saturated zone are not completely full of water; the pore spaces in the unsaturated zone are completely full of water

c. The pore spaces in the saturated zone are completely full of water; the pore spaces in the unsaturated zone are not completely full of water

Which of the following statements about rubidium-87 radiometric dating is true? a. The number of radioactive rubidium-87 atoms in an igneous rock is constant. b. The number of strontium-87 daughter products in an igneous rock is constant. c. The rate at which rubidium-87 decays to strontium-87 is constant. d. Rubidium-87 doesn't decay.

c. The rate at which rubidium-87 decays to strontium-87 is constant.

Groundwater represents how much of the world's fresh water? a. about 1% b. about 5% c. about 20% d. about 50%

c. about 20%

What was the maximum velocity of the 1925 Gros Ventre landslide in Wyoming? a. about one mile per hour b. about ten miles per hour c. about fifty miles per hour d. about two hundred miles per hour

c. about fifty miles per hour

Which of the folowing rocks has the highest permeability? a. an unfractured shale b. a cemented sandstone c. an uncemented sandstone d. all of these have approximately the same permeabilty

c. an uncemented sandstone

Which type of unconformity has sedimentary rocks both above and below the unconformity surface? a. angular unconformity b. disconformity c. both an angular unconformity and a disconformity d. nonconformity

c. both an angular unconformity and a disconformity

The process that mobilizes (transports) the particles produced by weathering: a. deposition b. diagenesis c. erosion d. pickup

c. erosion

Which of the following materials has the lowest porosity? a. shale b. gravel c. granite d. sandstone

c. granite

Which of the following reservoirs contain the most available fresh water on Earth? a. atmosphere b. biosphere c. groundwater d. lakes and rivers

c. groundwater

During an earthquake, water saturated sand can behave like a liquid, a process called _______________. a. slurrification b. unconsolidation c. liquefaction d. solifluction

c. liquefaction

Consider three undeformed horizontal beds of sedimentary rocks. Which layer is the oldest? a. upper layer b. middle c. lower d. All are the same age.

c. lower

The Jurassic is a geologic: a. epoch b. era c. period d. age

c. period

As sediment is transported downstream, the particles tend to become: a. rounded b. smaller c. rounded and smaller d. Sediment particles are harder than water; nothing happens to them

c. rounded and smaller

In which type of rocks are fossils most commonly found? a. igneous b. metamorphic c. sedimentary d. none of the above contain fossils

c. sedimentary

Carbon-14 is not useful for dating most rocks primarily because: a. there are no carbon-bearing rocks. b. carbon-14 in rocks doesn't break down. c. the effective dating range is much too short to be useful for most rocks. d. carbon-14 doesn't have a constant half-life.

c. the effective dating range is much too short to be useful for most rocks.

Which of the following sedimentary rocks has the largest particle sizes? a. sandstone b. shale c. conglomerate d. siltstone

conglomerate

Sedimentary rocks are a primary source of information about: a. past climates. b. evolution of life on Earth. c. energy resources. d. all of the above.

d. all of the above

Sediment is deposited as: a. strong currents accelerate. b. weak currents accelerate. c. ice flows. d. currents slow down.

d. currents slow down.

Which of the following combinations make for the best groundwater reservoir? a. low permeability and low porosity b. low permeability and high porosity c. high permeability and low porosity d. high permeability and high porosity

d. high permeability and high porosity

The percentage of a rock's total volume taken up by pore space is called the ___________. a. permeability b. recharge c. aquifer d. porosity

d. porosity

Marine terraces in coastal California are composed of ____________ and form as a result of _________. a. limestone; rapid uplift b. shale; gradual erosion c. sand/silt/clay; gradual erosion d. sand/silt/clay; rapid uplift.

d. sand/silt/clay; rapid uplift.

The accumulation of rocks at the base of a cliff is called _____________. a. a dune b. soil creep c. an alluvial fan d. talus

d. talus

The weathering process is subdivided into: a. rapid and slow b. physical and chemical c. high and low d. interior and exterior

physical and chemical