Deserts and Glaciers
What is the relationship between water currents and cross beds?
Cross beds sit at an angle to current direction.
Which of the following is true about sand dunes?
Dunes move over time.
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.
Explain why post A has moved farther than posts B and C. (Showing the photo of the posts in a line and then 8 years later, the posts are in a U shape downslope)
Ice in the center of a glacier has the least friction with the surrounding bedrock and can flow faster.
What are cross beds?
Inclined layers in sediment or sedimentary rocks that reveal the direction of wave or wind transport
What is cross bedding?
Layers deposited on a dune slip face that are inclined in the direction of wind transport.
Why do desert dunes migrate?
Wind erodes material on the back side of the dune and deposits it on the front side of the dune.
Will plucking occur if a glacier is NOT advancing?
Yes, because glacial ice is still moving inside the glacier even if the glacier's front is not advancing.
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 an end moraine?
a ridge of debris deposited at the end of a glacier
What glacial feature is circled in Figure 1? (The part between two small U shapes)
arête
Barchanoid dunes are an intermediate form of __________.
barchan and transverse dunes
Which way does ice flow in a glacier retreating uphill?
downslope
During a glacial retreat, a glacier will flow _____ while the terminus moves _____.
forward; backward
What glacial feature is circled in Figure 2? (Showing a pointy mountain top)
horn
Where do glaciers form?
in places where more snow falls in the winter than melts away in the summer
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
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
Desert regions occur __________, and always have a(n) __________ climate zone adjacent to them.
on every continent; steppe
__________ are defined as a chain of glacial lakes where each lake flows into the next.
pater noster lakes
How do pieces of rock move under the influence of wind?
rolling, sliding, bouncing, suspension
What is the term for the rolling and bouncing of sand grains during transport?
saltation
When air __________, it is compressed and warmed.
sinks
What property of a piece of material will most directly determine how it is carried by wind?
size
Cross-bedded sandstone shows inclined beds in a downward direction. What part of the ancient dune do these features represent?
slip face
What is the snowline?
the elevation above which snow persists throughout the year
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
What do cross beds represent?
the moving front of a ripple or dune
What is the zone of wastage?
the part of a glacier where snow melting exceeds snow accumulation
What is dust?
the particles carried in suspension by wind
Deserts that lie outside of the subtropics and mid-latitude belts are most likely the result of __________.
the presence of a rainshadow
Precipitation occurs on the __________ of the mountain range, while the __________ is dry.
windward side; leeward side
Which type of glacial movement is circled in Figure 1? (showing the smaller amount of movement towards the bottom of the glacier)
basal sliding
At what latitudes do the large-scale, convection cells bring dry air downward toward the Earth's surface?
between 20-30° north and south
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.
Which of the following describes favorable conditions for transverse dune formation?
Areas with steady prevailing winds and abundant sand
Which of the following budget scenarios describes a glacial advance?
More ice and snow accumulates than melts each year.
How does an end moraine form?
Pieces of rock are transported to the front of a glacier as ice within the glacier moves.
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.
How would a snow line on a glacier move as a glacial front is advancing?
The snow line would move downslope.
What is the best way to describe the shape of a glacial valley?
U-shaped
