Question 1

Abrasion of sediment particles results in which of the following?

Accepted Answer

Abrasion results in sediment particles becoming smaller and more well-rounded due to the constant grinding and bumping against other particles during transportation.

Question 2

In what type of rocks are you most likely to find oil, natural gas, and coal?

Accepted Answer

Oil, natural gas, and coal are all fossil fuels, which are formed from the decayed organic matter of plants and animals. Sedimentary rocks are formed from layers of sediment and are where most fossil fuels are found because they have accumulated over millions of years. Igneous and metamorphic rocks are formed from molten magma and existing rocks, respectively, and are less likely to contain fossils or organic matter.

Question 3

The pressure on sediment that is buried to a depth of 4 km is approximately ___ times atmospheric pressure.

Accepted Answer

The pressure on sediment that is buried to a depth of 4 km is approximately 1000 times atmospheric pressure. This is because the pressure of the overlying sediment increases with depth, and at a depth of 4 km, the pressure is about 1000 times greater than the pressure at the surface.

Question 4

Most shells of marine organisms are composed of

Accepted Answer

The majority of marine organisms have shells composed of calcium carbonate, which includes materials such as aragonite and calcite.

Question 5

Which of the following is a common product of the weathering of silicate rocks?

Accepted Answer

Clay minerals are a common product of the weathering of silicate rocks, as they form from the breakdown of feldspar and other silicate minerals in the presence of water and carbon dioxide. Pyroxene and amphibole are also silicate minerals, but they are less likely to form clay minerals as a product of weathering.

Question 6

Which kind(s) of sediment accumulate(s) where transport currents are strong?

Accepted Answer

Gravel is the best choice as it requires high energy transport currents to be moved, which indicates that the currents are strong. Mud particles are smaller and can be moved by weaker currents.

Question 7

Clastic sediments are much more abundant in Earth's crust than are chemical and biological sediments.

Accepted Answer

Clastic sediments, which are made up of fragments of pre-existing rocks, are the most common type of sediment on Earth's surface. Biological and chemical sediments, which come from the remains of organisms or the precipitation of minerals from solution, respectively, are less common.

Question 8

In a desert environment, the primary transport agent is/are

Accepted Answer

In a desert environment, water is scarce and therefore rivers and lakes are not common. Wind, on the other hand, is a strong and consistent force that shapes the landscape by eroding rocks and carrying sand and dust. It also helps distribute seeds and spores, which is vital for the survival of certain plant species. Thus, wind is the primary transport agent in a desert environment.

Question 9

Which of the following geologic processes causes the subsidence observed in newly forming rift valleys?

Accepted Answer

Lithosphere thinning leads to the stretching and thinning of the crust, which causes subsidence in newly forming rift valleys.

Question 10

The thick accumulations of sediment on the North American Atlantic margin are the result of which geologic process?

Accepted Answer

The thick accumulations of sediment on the North American Atlantic margin are primarily due to thermal subsidence, which occurs after the initial rifting phase. As the lithosphere cools and becomes denser, it subsides, creating space for sediments to accumulate over time.

Question 11

Assuming the sand dune was deposited by wind currents, which way was the wind blowing?

Accepted Answer

The sand dune has a gentle slope on the windward side and a steep slope on the leeward side. This indicates that the wind was blowing from the direction of the gentle slope, which is the left-hand side of the image. Choice B shows the wind blowing from left to right, which is the correct direction.

Question 12

The diagonal layers are called ________.

Accepted Answer

Diagonal layers in sedimentary rocks are formed by wind or water currents that create angled layers, which are called cross-beds. Graded beds refer to a sequence of sedimentary layers that have different grain sizes, while point bars refer to curved deposits of sediment along the inside curve of a meandering river. Ripples are small waves or undulations on the surface of sedimentary rocks.

Question 13

-In what type of environment did the ripples depicted above most likely form?

Accepted Answer

The ripples are symmetrical and have a wavelength of about 10 cm, which is typical of ripples formed by waves on a beach.

Question 14

-In which of the following sedimentary environments would you be most likely to find symmetrical ripples?

Accepted Answer

Symmetrical ripples are typically formed in environments where water movement is back and forth, such as on beaches, due to the action of waves.

Question 15

Bioturbation structures in sedimentary rock are evidence of

Accepted Answer

Bioturbation structures, such as burrows and trails, are created by organisms that live in or on the sediment, and disturb it as they move about. This is common in marine environments, where many species burrow into the sediment for protection, feeding, or both.

Question 16

Graded bedding is a common sedimentary structure in which environment?

Accepted Answer

Graded bedding is a common sedimentary structure in deep water environments such as continental slopes. It occurs when sediment is rapidly deposited and settles with the largest particles at the bottom and the smallest on top, creating a graded layer.

Question 17

Which of the following sedimentary environments is not characteristically a siliciclastic sedimentary environment?

Accepted Answer

Coral reefs are primarily composed of carbonate sediments, not siliciclastic sediments. A glacial environment, a desert environment, and a beach environment are all siliciclastic sedimentary environments.

Question 18

Chemical sedimentary environments are found only in marine settings.

Accepted Answer

Chemical sedimentary environments can be found in both marine and non-marine settings. Examples of non-marine chemical sedimentary environments include salt flats, hot springs, and evaporite deposits in arid regions.

Question 19

During diagenesis the sediments may undergo ___ changes.

Accepted Answer

During diagenesis, sediments can undergo both physical changes such as compaction and consolidation, as well as chemical changes such as mineral precipitation and dissolution, oxidation, reduction, and recrystallization.

Question 20

Compaction reduces both the volume and porosity of buried sediments, whereas cementation reduces the porosity of sediments and leaves the volume unchanged.

Accepted Answer

Compaction involves the reduction in volume and porosity of sediment as a result of the weight of overlying material. Cementation involves the filling of pore space within sediment by minerals, which reduces porosity but does not affect volume.

Quiz 6: Sedimentation: Rocks Formed by Surface Processes