Topic 5. Soil Systems (Erosion)

Which of the following best states the relationship between erosion and deposition?

• A.When the energy transporting sediments diminishes, the sediments settle in a low-lying area; therefore, deposition always follows erosion.

• B.When the energy transporting sediments diminishes, the sediments settle in a low-lying area; therefore, erosion always follows deposition.

• C.When rock is broken down into sediments, the sediments are eventually transported to another location; therefore, deposition is a form of erosion.

• D.When rock is broken down into sediments, the sediments are eventually transported to another location; therefore, erosion is a form of deposition.

According to Hjulstrom's diagram, below, what will happen to below-average-sized grains of sand in a river traveling 10 cm/s?

• A.The sand grains will not move from the riverbed.

• B.The sand grains will be eroded.

• C.The sand grains will be deposited.

• D.Depending on their composition, the sand grains may be eroded or deposited, or they may not move from the riverbed.

Erosion happens at the starred location on the mountain below. Where are the eroded materials most likely to be deposited?

• A.A

• B.B

• C.C

• D.D

Deposition, erosion, and weathering are related processes. Which answer choice lists these processes in the order in which they happen to sediment, from first to last?

• A.deposition, erosion, weathering

• B.erosion, deposition, weathering

• C.weathering, deposition, erosion

• D.weathering, erosion, deposition

A student observes sediments as they are carried downstream by a rapidly flowing river. The student argues that the river is depositing the sediments. Is the student correct?

• A.Yes. The river is depositing the sediments.

• B.No. Deposition is the movement and eventual settling of whole rocks, not rock fragments and sediments.

• C.No. The river is eroding the sediments; deposition will happen when the river slows and the sediments settle on the riverbed.

• D.No. The sediments still have the same chemical composition as the rock they came from; deposition follows chemical changes only.

River A flows at a velocity of 100 cm/s. River B flows at a velocity of 5 cm/s. River C flows at a velocity of 0.5 cm/s. A student has grains of silt and very coarse sand, as well as pebbles. Which river should the student throw each sediment type into, if the student wants to observe the deposition of each sediment type?

• A.The student should throw the silt in river A, the coarse sand in river B, and the pebbles in river C.

• B.The student should throw the silt in river C, the coarse sand in river B, and the pebbles in river A.

• C.The student should throw the coarse sand in river A, the pebbles in river B, and the silt in river C.

• D.The student should throw the coarse sand in river C, the pebbles in river B, and the silt in river A.

Which of the following scenarios illustrates the saltation of sediment?

• A.A river flows too slowly to move sediment along the riverbed.

• B.A slowly flowing river slides or rolls sediment along the riverbed.

• C.A rapidly flowing river carries sediment all the way downstream to the sea.

• D.A river flowing at a moderate velocity picks up sediment and carries it a short distance; when the river slows, the sediment falls to the riverbed.

What is the difference between erosion and deposition?

• A.Erosion is the breaking down of rocks into sediments by physical or chemical processes; deposition is the accumulation of sediments in low-lying areas due to the action of gravity, water, ice, or wind.

• B.Erosion is the accumulation of sediments in low-lying areas due to the action of gravity, water, ice, or wind; deposition is the breaking down of rocks into sediments by physical or chemical processes.

• C.Erosion is the removal of sediments by gravity, water, ice, or wind; deposition is the accumulation of sediments in low-lying areas due to the action of gravity, water, ice, or wind.

• D.Erosion is the breaking down of rocks into sediments by physical or chemical processes; deposition is the removal of sediments by gravity, water, ice, or wind.

Glaciers can advance over regions of Earth's surface over thousands of years. What is the most substantial impact that the advancing ice sheet causes to the land?

• A.The glacier picks up and transports rocks and sediments of all shapes and sizes as it moves across the land.

• B.The glacier leaves behind rocks and sediments of all shapes and sizes as it moves across the land.

• C.The glacier changes the chemical composition of rocks that it passes over as it moves across the land.

• D.The glacier tears holes in Earth's crust as it moves across the land, and rocks fall through and are recycled in the mantle.

A student observes a rock that has been split by the roots of a tree, scattering sediment at the base of the rock. The student argues that the rock has been eroded by the tree roots. Is the student correct?

• A.Yes. The rock has been eroded by the tree roots.

• B.No. The rock has been broken down into sediments; erosion happens only when gravity pulls the sediments to the lowest possible part of the region.

• C.No. The rock has been weathered by the tree roots; erosion happens only when wind, water, or another agent removes the sediments from the area.

• D.No. The sediment still has the same chemical composition as the rock; erosion happens only when agents such as acid or oxygen change the minerals that make up the rock.