Mastering Geology Ch. 15/16
Which dunes are formed under varying wind directions, but are dominantly parallel to the average direction?
longitudinal
Star dunes exhibit __________.
many ridges radiating from a central point
What is dust?
the particles carried in suspension by wind
What are crevasses and where do they form?
Crevasses are cracks that form in the zone of fracture at the top of the glacier. They form when tension is created as a result of the glacier moving over irregular terrain.
Which of the following is true about sand dunes?
Dunes move over time.
What are cross beds?
Inclined layers in sediment or sedimentary rocks that reveal the direction of wave or wind transport
In the first model, what happens as the layer of coarse material develops at the surface?
It blocks the fine-grained sediment below from the wind, which prevents the possibility of further deflation.
Cross beds are a preserved record of what?
The deposition of sand on the leeward side of a dune.
Why do desert dunes migrate?
Wind erodes material on the windward side of the dune and deposits it on the leeward side of the dune.
Deflation leads to the formation of desert pavement by __________.
carrying fine sediments away and leaving a layer of larger particles at the surface
Wind erosion can cause __________, which can create shallow depressions called __________.
deflation; blowouts
In the second model, wind energy diminishes between large grains of the surficial layer, leading to what?
deposition of fine-grained sediments between large grains
During a glacial retreat, a glacier will flow _____ while the terminus moves _____.
forward; backward
The cross bedding in a preserved layer of sandstone dips (tilts downward) to the East. What can be inferred about the wind direction at the time of deposition?
from west to east
Cross-bedded sandstone shows inclined beds in a downward direction. What part of the ancient dune do these features represent?
slip face
Which part of a glacier will see the build-up of ice and snow over the course of a full year?
Zone of accumulation
What is a playa commonly occupied by?
an ephemeral lake
Which of the following is the largest type of glacier?
an ice sheet
Which of the following describes favorable conditions for transverse dune formation?
areas with steady prevailing winds and abundant sand
Which way does ice flow in a glacier retreating uphill?
downslope
Which type of glacial movement will be responsible for the greatest amount of glacial flow?
internal flow
The __________ of a dune is characterized by a decrease in energy and sand avalanches, which occur due to oversteepening.
leeward side
How do pieces of rock move under the influence of wind?
rolling, sliding, bouncing, suspension
What property of a piece of material will most directly determine how it is carried by wind?
size
What feature is responsible for creating eskers?
streams that flowed below, in, or on the glacier
Which landform marks the furthest extent of an advancing glacier?
terminal moraine
What is cross bedding?
Layers deposited on a dune slip face that are inclined in the direction of wind transport.
Which one of the following is an evaporite mineral?
gypsum
Which is the best definition of glacial snow line?
the line dividing zones of accumulation and melting of ice at the surface of a glacier
Which two regions currently contain the world's last remaining ice sheets?
Antarctica and Greenland
Under what conditions will the front of a glacier remain stationary?
Glacial fronts remain stationary when melting and snow accumulation are equal.
How does a glacier lose ice through sublimation?
Ice changes from solid to gas.
What is the primary difference between the two desert pavement hypotheses?
Model 1 is based on a sediment volume decrease through time (erosion), while Model 2 is based on an increase in sediment volume through time (deposition).
Which of the following budget scenarios describes a glacial advance?
More ice and snow accumulates than melts each year.
How would a snow line on a glacier move as a glacial front is advancing?
The snow line would move downslope.
Barchanoid dunes are an intermediate form of __________.
barchan and transverse dunes
When was the last time North America had major ice sheets? View
18,000 yrs ago
What is the natural angle of repose for sand?
34 degrees
Which of the following is a difference between barchan and parabolic dunes?
A barchan exhibits a concave slip face, while a parabolic dune shows a convex slip face.
__________ are defined as a chain of glacial lakes where each lake flows into the next.
Pater noster lakes
What is the term for the rolling and bouncing of sand grains during transport?
Saltation
What does saltating mean?
Sand grains are lifted by the wind, leap a short distance, and then fall back to the ground.
How would you expect the front of a glacier to move if it undergoes a period of net accumulation, followed by net wastage, and finally a period of net accumulation?
The glacier's front would move forward, backward, and then forward again.
What is the best way to describe the shape of a glacial valley?
U-shaped