EES112: Exam 2

A rock is radiometrically dated to determine its age. The laboratory doing the dating discovers that the rock currently has 200 atoms of radioactive parent isotope and 600 atoms of stable daughter product. Assuming that the rock had 800 atoms of radioactive parent isotope and 0 atoms of daughter product at the time it formed, how old is the rock, if the half-life of the radioactive isotope is 1,000,000 years?

2,000,000 years

What is the minimum number of seismographs needed to locate an earthquake?

3

Based on radiometric age dating, what is the age of the Earth?

4.6 billion years.

Earthquakes occur at which of the following plate boundaries?

All of the above

Soft parts of organisms may be preserved (fossilized) by:

All of the above

Which of the following has been used to try and predict earthquakes that may occur in the near future?

All of the above.

Seismologists like to see a seismic gap along a fault segment because it indicates that no major earthquakes have occurred there for awhile and therefore are unlikely to occur in that area in the future.

False

Using the Principle of Cross-cutting relationships, a geologic feature (such as a fault) that cuts through another geologic feature (such as a layer of rock) must be older than the geologic feature being cut.

False

Which of the following cannot be dated with Radiocarbon (C-14) dating?

Granite.

When water saturated sediment suddenly loses its strength because of ground shaking during an earthquake, considerable damage may result to structures built on such sediment as the buildings settle into the earth. This phenomenon is known as:

Liquefaction.

Which of the following is the fastest type of seismic wave and can travel through solids, liquids, and gases?

Primary (or P) waves.

Pieces of rock found inside of other rocks are called inclusions. If you have a granite with a piece of sandstone included within it, which of the two rocks is older?

Sandstone.

Which of the following is most accurate concerning fault creep?

Seismologists are generally relieved to see evidence of considerable fault creep because it indicates that the fault segment is not locked and is less likely to be building up the amount of strain energy necessary for a large magnitude earthquake.

A fracture in the Earth's crust along which displacement occurs is called a fault.

True

A noted strike-slip fault in California is the San Andreas fault.

True

An unconformity is a period of erosion or nondeposition in the rock record.

True

Earthquakes are vibrations of the Earth caused by a rapid release of energy.

True

Radiometric age dates suggest that the Moon, Earth and meteorites are all about the same age.

True

The Mercalli Intensity scale is used to measure the amount of damage (destruction) caused by an earthquake.

True

Which of the following types of seismic waves travel through the Earth's interior?

a and b (i.e. both Secondary and Primary waves).

A trace fossil may include all of the following except:

a clam shell.

California is susceptible to the hazard of tsunamis. What is a tsunami?

a seismic sea wave usually generated by displacement along a fault on the seafloor. These waves, if sufficiently large, can inundate low lying coastal areas, killing many people and causing considerable destruction.

Graded bedding, cross-bedding, ripples, and mudcracks are sedimentary structures that

aid geologists in reconstructing paleoenvironments

In which of the following environments would you expect to find ripples?

all of the above

Major sedimentary depositional environments include:

all of the above

Which of the following can be caused (i.e. triggered) by an earthquake?

all of the above

Which of the following is a body fossil?

all of the above.

A fossil is best defined as:

any evidence of past life.

Which of the following radioactive isotopes is most useful for dating a very young sample (<20,000 years) of wood?

carbon-14

Which of the following cannot be dated with Potassium/Argon (K/Ar) dating?

clam shell

Which of the following types of sediment is most likely to be found in the deep ocean?

clay

A gastrolith is a type of rock formed when glaciers erode underlying bedrock. When the glacier melts, it exposes highly polished rocks called gastroliths.

false

Most fossils are the preserved:

hard parts of organisms.

Where would you find a playa?

in a desert

The Principle of Superposition recognizes that:

in an undisturbed sequence of sedimentary rocks, the oldest rocks are on the bottom of the sequence and the youngest are at the top.

When fine sediment (silt and clay) is deposited in water, and then the water evaporates exposing the sediment to the air, the following sedimentary structure may form.

mudcracks

An erosional contact between an intrusive igneous rock that is overlain by sedimentary rock is known as a(n):

nonconformity.

Most fossils are found in:

sedimentary rocks.

What is the correct clastic rock sequence that indicates increasing grain size of the sediment forming the rock?

shale, sandstone, conglomerate

The Richter scale is one method used to describe the magnitude of an earthquake. The magnitude of an earthquake is a measure of:

the energy released by the earthquake.

The Principle of Uniformitarianism states that:

the geologic processes that operate on Earth today are the same processes that operated on Earth in the geologic past (i.e. the present is the key to the past).

An epicenter is:

the point on the earth's surface directly above the focus of an earthquake

Localized environmental features such as lagoons, deserts, and lakes can be identified in the rock record by studying

the sedimentary rock record

When glaciers melt they leave behind ridges of poorly sorted, conglomerate (gravel) called:

till (i.e. moraines).

A clastic rock formed of fine-grained sediment like clay suggests a depositional environment with little or no current velocity.

true

A gastrolith is an example of a trace fossil.

true

A half-life is the amount of time it takes for one half of a radioactive parent isotope to decay (i.e. change into) its stable daughter product(s).

true

Braided streams are common in mountainous areas where there is a large supply of fairly coarse-grained sediment, where water discharge is variable throughout the year and stream gradients are high.

true

Index fossils are species that existed for a short period of time on Earth and thus are useful for determining the age of the rocks in which they are preserved.

true

Petrified wood is formed by the process of permineralization, which is a form of petrifaction.

true