Question 1

What is the cause of most earthquakes?

Accepted Answer

Sudden movements from elastic strain release and rupture along pre-existing faults on or near plate boundaries, known as tectonic earthquakes, are the most common cause of earthquakes. These occur as tectonic plates shift and create stress along fault lines, which then release in the form of an earthquake. The other options (A, B, and D) may be associated with certain seismic events but do not represent the primary cause of most earthquakes.

Question 2

How wide is the San Andreas Fault Zone at its northern and southern ends?

Accepted Answer

The San Andreas Fault Zone is approximately 10 kilometers wide at its northern and southern ends.

Question 3

A ________ is a planar fracture in rock along which there has been no displacement.

Accepted Answer

A joint is a planar fracture or crack in rock along which there has been no displacement. It is a natural way in which rocks break in response to stress without any appreciable movement along the fracture surface.

Question 4

________ joints form when igneous rocks cool and develop pillar-like columns.

Accepted Answer

Columnar joints form when igneous rocks cool and develop pillar-like columns. This occurs due to contraction during cooling, resulting in cracks forming in polygons that resemble columns.

Question 5

A deeply eroded, structural basin would exhibit ________.

Accepted Answer

A deeply eroded structural basin typically has inward-dipping strata that form circular patterns, with younger rocks in the center and older rocks exposed around the edges.

Question 6

Name two landforms or distinctive landscape features that mark the trace of the San Andreas Fault.

Accepted Answer

Long straight escarpments, narrow ridges, and sag ponds are distinctive landscape features that mark the trace of the San Andreas Fault.

Answer: D
 Hot springs and active geyser fields in central California are also associated with the San Andreas Fault. However, they may not necessarily mark the trace of the fault directly.

Question 7

A ________ is a prominent angular ridge formed by the differential erosion of tilted, alternating hard and soft strata.

Accepted Answer

A hogback is a type of ridge that is formed by the differential erosion of tilted, alternating hard and soft strata. The alternating layers of hard and soft rock form a steep slope on one side and a gentle slope on the other. The name "hogback" comes from the fact that the ridge resembles the spine of a hog or pig. Mesas are flat-topped mountains, wadis are dry riverbeds that only fill with water during the rainy season, and a scarp face is a steep slope or cliff face. None of these options fit the description of a prominent angular ridge formed by the differential erosion of tilted, alternating hard and soft strata.

Question 8

The two different sides of a dip-slip fault are called ________.

Accepted Answer

The correct terms for the two different sides of a dip-slip fault are the footwall, which is the block of rock beneath the fault, and the hanging wall, which is the block of rock above the fault. Choices A and D are not valid or commonly used terms, while choice B is not a recognized term.

Question 9

When folding occurs, rocks situated in the hinges (on the axes)of the folds are ________.

Accepted Answer

The answer of When folding occurs, rocks situated in the...

Question 10

Which one of the following best describes the geology of the Black Hills region in South Dakota?

Accepted Answer

The Black Hills region is an elongate upwarped dome, as described in option D. The dome is flanked by hogbacks of the Dakota Sandstone, and older crystalline igneous and metamorphic rocks core the dome. Options A, B, and C do not accurately describe the geology of the region.

Question 11

Broad downwarps in the basement rock may deform the overlying sedimentary cover strata to generate large elliptical to circular folds called ________.

Accepted Answer

Broad downwarps in the basement rock may deform the overlying sedimentary cover strata to generate large elliptical to circular folds called basins.

Question 12

There were 11 earthquakes M>6.9 on the San Andreas Fault between 1812 and 1994.On average, how many years pass between earthquakes of this size, somewhere along the fault?

Accepted Answer

To determine the average time between earthquakes of this size on the San Andreas Fault, we can take the total time span between the first and last earthquakes (182 years) and divide by the number of earthquakes (11-1=10, since we're measuring the time between events). This gives us an average of 18.2 years. Rounded to one decimal place, the answer is 16.5 years.

Question 13

Which statement is not true about joints?

Accepted Answer

Joints are fractures in rocks along which there has been no significant movement parallel to the surfaces of the fracture. They are typically formed by brittle deformation, not ductile deformation. Ductile deformation refers to the process by which rocks deform under stress by flowing and folding, without fracturing, which is not how joints are formed.

Question 14

Joints in rocks are characterized by ________.

Accepted Answer

Joints in rocks are fractures or separations in rocks along which there is no appreciable displacement or movement of the blocks on either side of the fracture. These fractures are typically parallel and can be closely spaced, but they do not involve movement of the blocks in opposite directions as seen in faults. The other options listed (A, B, and D) describe different types of faults or structures that are not associated with joints.

Question 15

The Michigan geologic map shows older Precambrian crystalline metamorphic rocks, surrounding Paleozoic marine strata (in roughly circular patterns), surrounding a central core area of Carboniferous rocks.What is this structure?

Accepted Answer

A basin is a geological structure where younger rocks are found in the center, surrounded by progressively older rocks, which matches the description given.

Question 16

Considering the largest earthquakes to occur along the San Andreas Fault, which was the most damaging?

Accepted Answer

The 1906 San Francisco earthquake had a magnitude of 7.9 and caused widespread damage and destruction, including the collapse of buildings, fires, and over 3,000 deaths. It was the most damaging earthquake known to have occurred along the San Andreas Fault.

Question 17

Normal and reverse faults are characterized mainly by ________.

Accepted Answer

Normal and reverse faults are both types of dip slip faults, meaning that the movement is mainly up or down along the fault plane. Strike slip and horizontal slip are types of faults where the movement is mainly horizontal. Camisole slip is not a recognized type of fault.

Question 18

Vertical displacements along dip-slip faults can produce long low breaks in the landscape or cliffs called ________, that can show the relative sense of motion across the fault.

Accepted Answer

Fault scarps are long low breaks in the landscape or cliffs that are produced by vertical displacements along dip-slip faults. They can show the relative sense of motion across the fault. A, C, and D are not correct terms for this feature.

Question 19

Broad upwarps in the basement rock may deform the overlying sedimentary cover strata to generate large elliptical to circular folds called ________.

Accepted Answer

Broad upwarps in the basement rock can result in the formation of domes in the overlying sedimentary cover strata. Anticlines, doubly plunging synclines, and monoclines are formed by other types of deformation.

Question 20

When rock is broken and pulverized as the sides of a fault grind past each other, this generates a loosely coherent, easily moved and easily eroded material called fault ________.

Accepted Answer

The material generated as the sides of a fault grind past each other is known as fault gouge.

Quiz 9: Crustal Deformation