Geology Final

Which of the following geologic settings would most likely produce the greatest amount of rock deformation?

A convergent plate boundary

The structure shown in the vertical cross section (in Figure 16.1) is an example of a ______.

A reversed fault.

What are tsunamis and what causes them?

A tsunami is a series of extremely long waves caused by a large and sudden displacement of the ocean, usually the result of an earthquake below or near the ocean floor.

How do we know the outer core is liquid?

Because S-waves can't travel through it, but P-waves do.

What is the difference between surface seismic waves and body seismic waves?

Body waves can travel through the Earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water.

How do various kinds of seismic waves move?

Body waves- move through Earth's inner layers Surface waves- can only move along the surface of the planet like ripples on water

How does coal form? What are the main different types of coal?

Coal is formed from heat and pressure produced chemical and physical changes in the plant layers which forced out oxygen and left rich carbon deposits. 4 different types of coal: anthracite, bituminous, sub-bituminous, and lignite

Which of the following lists contains only fossil fuels?

Coal, oil, natural gas

Why are magnetic anomalies of continental crust so much more complicated than oceanic crust?

Continental contains abundant iron minerals, where as oceanic crust does not contain any iron minerals.

In what geological setting do the deepest earthquakes occur?

Core of sub-ducting slabs, that descend into the Earth's mantle from CONVERGENT PLATE BOUNDARIES.

What are the major compositional layers of the Earth and what are their most important characteristic?

Crust-the outermost solid layer of a rocky planet or natural satellite. Mantle-layer of the Earth between crust and outer core, not liquid, on very long time scales and under pressure it can flow. Core-the innermost layer of the Earth, composed of iron and nickel.

Two geological layers in contact with one another are shown in figure 13.2. The solid ray in layer one represents an incoming seismic P wave ray and the dashed rays in layer 2 represent possible refracted P wave rays. If seismic velocities in layer 1 are lower than in layer 2, which of the possible refracted seismic rays shown in layer 2 is correct?

D

Which of the following tasks could not be accomplished by seismic reflection profiling?

Determining the chemical composition of a rock.

The type of deformation that the rocks have undergone in Figure 16.3 consists chiefly of _______.

Displacement

Figure 16.2 shows a pattern of circularly outcropping rocks, where the oldest rocks are in the center, and the rocks become progressively outwards.

Dome

How would you distinguish a geologic dome from a geologic basin in map view?

Dome-found where forces deep under the crust have thrust a portion of the Earth upward. Basin-similar, but overlaps face outward as the structure forms a depression.

What is the geologic significance of the Precambrian-Cambrian time boundary in Earth history?

Earliest part of Earth's history, set before the current Prianerozoic Eon. Accounts for 88% of the Earth's geologic time. Subdivided into 3 eons, Hadean, Archean, Proterozoic.

Why does Earth not have mountains as tall as Olympus Mons on Mars?

Earths high geothermal gradient causes crystal rocks to act ductility at mid crustal depths.

What is meant by elastic, brittle, and elastic rheology? How does the rheology of rocks change as applied stress increases?

Elastic-A temporary shape change that is self-reversing after the force is removed, so that the object will return to its original shape. Brittle-the breaking of chemical bonds which do not subsequently reform. Elastic rheology- principally concerned with extending continuum mechanics to characterize flow of materials.

What is the cause of most earthquakes?

Erosion

How is hydraulic fracturing ("fracking") used to extract petroleum & natural gas from the Earth?

Fracking is a drilling method, it cracks in and below the Earth's surface are opened & widened by injecting water, chemicals, and sand at high pressure.

Which of the following is least likely to experience earthquakes?

Geographic center of a techtonic plate.

What are the steps in the formation of a glacier?

Glaciers begin to form when snow remains in the same area year-round, where enough snow accumulates to transform into ice. Each year, new layers of snow bury and compress the previous layers.

How does basal sliding off a glacier occur?

Glaciers can slide because ice melts under pressure, resulting in a film of water at the ice bed interface... If water pressure become high enough, cavities can form at the ice bed interface, causing sliding with bed separation. This reduces basal friction and allows faster ice flow.

The worlds deadliest earthquakes have caused fatalities numbering in the ______________.

Hundred of thousands

Where do the formation of sets of narrow mountain ranges separated by basins typically occur?

In magmatic arcs

From the center of the earth to the surface of the earth, the correct order of earth physical layers is:

Inter core, outer core, lower mantel, transition zone, asthenosphere, lithosphere.

What does the principle of uniformitarianism state?

It holds that the same geologic processes we recognize in action today have been operating throughout the Earth's history to create the features we see in the geologic record.

What is karst topography? How does it form?

It is a landscape that is characterized by numerous caves, sinkholes, fissures, and underground streams. forms is regions of plentiful rainfall where bedrock consists of carbonate-rich rock, such as limestone, gypsum, or dolomite, that is easily dissolved.

Which statement about land subsidence is false?

Land subsidence is caused mainly by groundwater contamination.

S seismic waves are not able to travel which of the followings?

Liquids

Natural gas is predominantly composed of which of the following?

Methane

Which statement about groundwater is false?

More groundwater can be produced from a well in the unsaturated zone than from a well in the saturated zone.

Within a sequence of undisturbed sedimentary rock layer, where would the oldest layer be located?

On the bottom

Which of the following statements about nonmetallic mineral resources is false?

On the whole, nonmetallic mineral resource use is small compared to metallic resource use.

Which of the following statements about orogeny (mountain building) is false?

Orogeny has never occurred in the cratons of continents.

The type of seismic wave motion represented by figure 13.1 is characteristic of ____________.

P Waves

In general what are the type of seismic waves travel the fastest?

P waves

The Low Velocity Zone (LVZ) in the upper mantle is probably caused by which of the following?

Partial melting of mantle rock.

Which of the following sets of time devisions occur with in the Paleozoic?

Permian, Carboniferous, Devonian, Silurian, Ordovician, Cambrian.

Oil and natural gas are derived predominantly from the remains of which of the following?

Plankton

When groundwater is pumped out of a well, what effect does it have on the water table?

Pumping water out of the ground at a faster rate than it is replenished over the long-term causes similar problems. Excessive pumping can lower the ground water table, and cause wells to no longer be able to reach groundwater.

Which of the following statements about radiometric dating is true?

Radiometric dating can provide accurate numerical ages of minerals if the mineral has not lost or gained parent or daughter atoms after the mineral formed.

What is the source of most shallow groundwater in the Earth's crust?

Rainfall, water from plants

What are the principles of of relative dating?

Relative dating-placing of events in the order in which they occurred without any relationship to the actual time during which any one event occurred. Uniformitarianism- James Hutton, Natural processes such as erosion & deposition, plate tectonics and the laws of gravity and isostasy produce the features of the Earth. The principle of original horizontally-sediments deposited laterally in continuous layers. The principles of superposition-in a series of undisturbed layered rocks each successive layer above is younger than the layer below it. The principle of cross-cutting relationships-Any geologic feature that crosscuts or modifies another feature must be younger than the rocks that cut through it. The principles of inclusions- A rock that contains fragments or pieces of another rock must be younger than the pieces of another rock must be younger than the pieces of rock that it contains. The principle of baked contacts-Magma will heat/metamorphose or "bake" the rocks it comes in contact with.

In what kind of geologic media are seismic waves amplified the most?

Seimic waves travel faster thru hard rocks than softer rocks and sediments. Seimic waves are waves of energy admitted at the focus of the earth.

Which statement best describes short term earthquake predictions?.

Short term earthquake predictions have been largely unreliable.

What are common sources of groundwater contamination?

Storage tanks, septic systems, uncontrolled hazardous waste, landfills, chemicals and road salts, atmospheric contaminants.

Which of the following statements is false?

The average concentrations in which most metals exist in the Earth's crust are high enough to be mined economically.

The Mohorovicic boundary or Moho represents the boundary between which of the following?

The crust and the mantle

Which measurement is key in finding the location of the earthquakes of the epicenter?

The difference between the time the P wave arrives and the time the S waves arrive at multiple seismometer stations.

What does Darcy's law express?

The discharge rate q is proportional to the gradient in hydraulic head and the hydraulic conductivity.

What statement about the direction of the earth's magnetic field is true?

The earth's magnetic field has reversed frequently over earth's history.

Discribe the mechanism by which earthquakes occur along faults.

The elastic rebound theory suggest that if slippage along a fault is hindered such that elastic strain energy builds up in deforming rocks on-either side of the fault when the slippage does occur the energy released causes an earthquake.

Which of the following major layers in the earth is predominantly molted?

The outer core.

Why would sandstone shown in Figure 19.1 probably not be very permeable?

The pores in the sandstone are not very interconnected.

What effect does the formation and melting of continental-scale glaciers have on the Earth's lithosphere?

The weight of glacial ice sheets depress the lithosphere into the mantle causing crust to subside. After the ice melts, the depressed lithosphere rebounds. The rebound process. is still taking place today.

What are the main kinds of geologic traps for petroleum and natural gas?

There are 2 major categories of traps, structural, and stratigraphic.

What are the main landforms produced by glaciers?

U-shaped valleys, Fjords, and Hanging Valleys, Cirques, Nunataks, Aretes, and Hornes

What element is most commonly used in the production of nuclear energy?

Uranium

Why are sedimentary rocks typically deposited in a horizontal orientation?

Varies horizontally due to differences in the energy conditions and distance from the origin of the sediments. Also formed from fragments of rocks.

What are warning signs of an imending earthquake?

Water levels, radon gas in spring water, electrical signals emitted by minerals, or agitation of animals are similarly unsubstantial.

What is the relationship of the water table to the land surface?

Water tables often follow the topography, or upward and downward tilts, of the land above them. Sometimes a water table runs intersects intersecting with the surface.

What are the main "alternative energy" resources under consideration today, and what are their respective advantages and disadvantages?

Wind power-pro:produces no pollution and will never run out, con: it is intermittent & need continuous wind Solar power-pro:renewable resource as long as the sun exists, con: doesn't produce energy if the sun isn't shining and expensive power stations Geothermal energy- pro:if done correctly produces no harmful by-products, con: if done incorrectly can produce pollutants Hydroelectric energy- pro:hydroelectric power stations can increase, con: Dams are expensive to build.

What is hydraulic head?

a specific measurement of a liquid pressure above a vertical datum.

What is a "hypothermal" ore deposit?

accumulation of valuable minerals which formed from hot waters circulating in Earth's crust through fractures. Creates rich-metallic fluids concentrated in a selected volume of rock, which becomes supersaturated and then precipitates ore minerals.

Which of the following is a type of evidence for the presence of a fault?

all of the above

Which statement about the over use of groundwater is true?

all of the above

What is the largest division of time in the geologic time scaled called?

an eon

What is an aquifer?

an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well

What do anticlines and synclines look like in cross section and in map view?

anticline-appears as parallel beds of the same rock that dip from the center and fold syncline-appears as a set of parallel beds that dip toward the center.

What kind of information do gravity surveys provide about the Earth?

can detect natural or man-made voids, variations in the depth bedrock, and geologic structures of engineering interest.

What are the main environmental impact of mining?

can pollute air and drinking water, harm wild-life and habitat and permanently scar natural landscapes.

Which kinds of geologic conditions promote the formation of folds in rocks?

compressional stress-when rock is being pushed inward from both sides.

Why do continental lithosphere and magmatic island arcs not slide down subduction zones?

continental lithosphere is less dense than oceanic lithosphere so the latter always subducts beneath the former. Andesitic magma rises from the subduction zone to form a magnetic arc on the continental crust.

What factors affect the speed and direction of groundwater flow?

controlled by the permeability of the aquifer through which the water is flowing and by the local hydraulic gradient.

A positive gravity anomaly within a surveyed section of the earths crust could be caused by rocks that are locally ____ than the surrounding rocks.

denser

A rock that has undergone a change in shape as a result of an applied stress, but that will return to its original shape after the stress has been removed is said to be ____.

elastic

What are some ways in which contaminated groundwater can be cleaned up?

eliminate the pollution source, monitor the extent of the pollutant, engage in remediation

What kinds of geologic evidence indicates the presence of a fault?

faults visibly displace distinct layers in rock, so that the layers on on one side of a fault don't connect to layers on the other side.

Within increasing depth below the Earth's surface, the salinity of groundwater typically ____.

increases

What is the difference between a joint and a fault?

joint-fracture along which no movement has taken place. usually caused by tensional forces. fault-fracture or break in the rock along which movement has taken place.

Caves and karst topography are most likely to develop in _____ rock that is relatively easily dissolved by groundwater.

limestone

What are the major physical layers of the Earth and what are their most important characteristics?

lithosphere-outermost and rigid layer mechanical layer. includes the crust and the top of the mantle. asthenosphere-underneath the lithosphere. under mantle that flows, but no liquid mesosphere-beneath asthenosphere. Material flows but slower than asthenosphere. outer core-layer of liquid iron and nickel beneath the mesosphere, layer of the Earth that is true liquid

In a sequence of horizontal strata, a feature such as a fault or igneous rock body (such as a dike) that cuts across the strata ________.

must be younger than the strata.

What are the steps in the formation of a conventional petroleum of natural gas deposit?

process begins when organic debris settles with sediment. As the burial increases, heat & pressure transform the sediment into organic shale in which organic matter becomes kerogen. At appropriate temperatures, kerogen becomes oil, which seeps upward.

Open pit mines are favored over underground mines for ______.

shallow ore deposits

What is meant by "strike" and "dip"?

strike-direction of the line formed by the intersection of a rock surface with a horizontal plane dip-acute angle that a rock surface makes with a horizontal plate

How do the characteristics of groundwater change with increasing depth?

takes more money and energy the deeper and lowered the water table.

Which of the following geologic features is NOT a common trap for oil and natural?

Caldera

What are the common source of rocks for oil and gas?

Fine-grained sedimentary rocks

_____ dating is the task of placing rock units and geologic events in their proper sequence?

Relative

Which statement about hydraulic head is false?

The greater the hydraulic head gradient, the lower the velocity of groundwater flow.

Which of the following is a common source of groundwater contamination?

all of the above

What is meant by positive and negative magnetic anomalies?

positive magnetic anomalies-reading that exceeds the average magnetic field negative magnetic anomalies-reading that is lower than the average magnetic field.

In what kind of geologic environments would you most likely to find tensional, compressional, and shearing stresses, respectively? What kinds of geologic structures are produced by these different kinds of stresses?

tensional-rocks being pulled in opposite directions compression-squeezes rock together until if folds or breaks shearing-causes rock to be distorted from side to side

If 16 radioactive parent atoms decayed to half of their original number after one year, how many radioactive parent atoms would be left after 2 years?

4

The "oil window" where temperature and pressure are optimal for the formation of oil typically occurs at depths of _____.

4 to 6 km

what is the age of the Earth currently accepted by most of the geologic research community?

4.54 billion years old

What are fossil fuels? How much of U.S. energy consumption is provided by fossil fuels?

A fossil fuel is formed by natural processes, such as anaerobic decomposition of buried dead organism, etc. The U.S. uses 80% of their fuel from fossils fuels.

How much stronger is a magnitude 5 earthquake than a magnitude 4 earthqake?

A magnitude of 5 earthquake is 10 times stronger tthan a magnitude 4 earthquake.

Which of the following statements about unit A is correct (see Figure 16.5)? Note that the small rock bodies pointed to by the arrows are also part of A.

A must be older than X.

Which of the following building constructions would be safest during an earthquake?

A single story wood frame house.

How are the principles of radioactive decay used to date rocks?

A technique used to determine the age of materials such as rocks. Based on comparison between the observed abundance using known decay rates.

What are the main ingredients of concrete?

Air, cement, water, and sand

Which of the following is a hazard commonly associated with earthquakes?

All of the above

Which term is used to describe rock or sediment layer that has low permeability and hinders the movement of groundwater?

Aquitard

Which statement about the water table is true?

All of the above

Which of the following statements about alternative (non fossil fuels) energy resources is false?

Alternative resource usage now accounts for the majority of energy used worldwide.

The bold line shown in the sedimentary rock package shown in Figure 16.4 represents an ____.

Angular unconformity

What are the differences between angular unconformities, nonconformities, and disconformities?

Angular-strata is deposited on tilted and eroded layers. Nonconformities- develops where sediments are deposited on top of an eroded surface of igneous or metamorphic rocks. Disconformity-exists where the layers above and below an erosional boundary have the same orientation.

What are the characteristics of an index fossil?

Any animal or plant preserved in the rock record of the Earth that is a characteristic of a particular span of geologic time or environment.

How are the glacial striations and glacial polish produced?

As glaciers pour off the mountain highlands, thtey carry vast quantities of weathered and eroded rock. When the rock lands, ice scrapes against the mountain valleys, scratch marks or "striations" develop parallel to the glacier's path.

Which of the following would be least likely to contribute to folding of a horizontal layer of rock?

Brittle rheology in the horizontal rock layer

Three large (Mw 7.0-7.4) earthquakes struck near which of the following Missouri towns in 1811-1812.

New Madrid

What are the differences between normal, reverse and strike-slip faults?

Normal-a dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block. Reverse-the hanging wall moves upward relative to the footwall. caused by compressional tectonics. Strike-slip--experiences lateral motion, movement is horizontal, along the line of the strike of the fault.