Geology 1301 Chapter 4
___ are long, linear scratch marks carved onto bedrock by glacial abrasion.
Glacial striations
A dry, flat lake bed
Playa
Coarse-grained sediments such as pebbles and cobbles often comprise the ________ in desert environments.
desert pavement
Deflation may lead to ________.
desert pavement, Loess, dust storms
Which glacial feature indicates the maximum extent of a glacier?
terminal end moraine
Which glacier deposit are drumlins mainly composed of?
till
Where is the world's largest ice sheet located today?
Antarctica
An apron of sediment along a mountain front created by the coalescence of alluvial fans
Bajada
Define dry climate. How extensive are the desert and steppe regions of Earth?
Dry climate is a climate in which yearly precipitation is less than the potential loss of water by evaporation. Desert and steppe regions cover about 30 percent of Earth's land surface.
Which of the following statements characterizes ephemeral streams?
Ephemeral streams flow only at certain times of the year.
A sinuous ridge composed of sand and gravel is a(n) ________; it is a deposit made by streams flowing in tunnels within or beneath glacial ice.
Esker
Which of the below are depositional features created by glaciers?
Eskers, Drumlins, outwash plains, kames
When a glacial trough is "drowned" by the sea, the result is a(n) ________.
Fiord
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
Which of the following responses best defines the movement of ice within a glacier?
Glacial movement is always in a downslope direction.
Which of the following is NOT a variety of moraine?
Hanging
Large bedrock knobs projecting above a sediment-filled basin
Inselberg
___ are steep-sided hills composed mostly of stratified drift.
Kames
Which of the following is an example of a glacial deposit?
Moraine
____ are defined as a chain of glacial lakes where each lake flows into the next.
Pater noster lakes
Center of basin where streams flow and briefly accumulate before evaporating or infiltrating bedrock
Playa lake
Encrusted salt layer left behind once water evaporates
Salt flat
How is desert different from steppe?
Steppe is more humid than desert.
During the Cold War, a B-52 bomber accidentally dropped an unarmed nuclear device on the Greenland Ice Sheet. Upon returning to the drop zone many years later, the device had gone missing. As a glaciologist on the project, where should you look for the missing device?
To find it you should go downslope from the drop zone, in the direction of ice flow.
When desert pavement is produced in a desert, why do the larger particles accumulate on the surface?
The wind can move particles of only a very specific size and it takes away these small particles, concentrating the larger ones.
What is the largest type of glacier?
an ice sheet
What is an ephemeral stream?
an intermittent stream that carries water only in response to specific episodes of rainfall
In an area of alpine glaciation, sinuous, sharp-edged ridges called ________ and sharp, pyramid-like peaks called ________ are common features.
arêtes; horns
What is the difference between till and stratified drift?
Till is an unsorted type of glacial drift, whereas stratified drift is sediment that is sorted according to the size and weight of particles.
What is the name used for cracks in the upper portion of a glacier?
crevasses
A rainshadow desert forms ________.
in places where mountain ranges act as barriers to the movement of water vapor
What are cross beds?
inclined layers in sediment or sedimentary rocks that reveal the direction of wave or wind transport
A(n) ________ is defined as a semiarid climate.
steppe
A fan-shaped deposit formed when a stream's slope is abruptly reduced
Alluvial fan
A(n) ________ is a cone of debris that forms where an ephemeral stream emerges from the confines of the canyon. Its runoff spreads over the gentler slopes at the base of the mountains and quickly loses velocity, dumping most of its sediment load within a short distance.
Alluvial fan
How do glaciers fit into the hydrologic cycle, and what roles do they play in the rock cycle?
-Glaciers play a role in the rock cycle by being dynamic erosional agents that accumulate, transport, and deposit sediment. -Glaciers fit into the hydrologic cycle when precipitation that falls at high elevations does not immediately make its way toward the sea. Instead, it may become part of a glacier. Ultimately, the glacial ice will melt into water, which will continue on its path to the sea.
Why is wind erosion relatively more effective in arid regions than in humid areas?
-Moisture in humid areas binds particles together, which inhibits wind erosion. -Vegetation in humid areas anchors down the soil, which inhibits wind erosion.
How does a medial moraine form?
A medial moraine is the result from the merging of two glaciers, causing their lateral moraines combining to form a medial moraine.
The terminus of a glacier will advance when which of the following conditions is met?
Accumulation of snow is greater than wastage.
Cirques often contain small lakes called ________.
Tarns
Cross beds are a preserved record of what?
The deposition of sand on the leeward side of a dune.
Relate the glacial budget to the two zones of a glacier.
The glacial budget is the balance or lack of balance between the gain of snow in the zone of accumulation and the loss of ice in the zone of wastage.
Why is it difficult to reconstruct the glacial episodes of the Pleistocene Ice Age from the glacial record on land?
The glacial record on land is punctuated by many erosional gaps.
Working in a mountain valley that contains an alpine glacier, you discover a series of end moraines in the valley. As you move up toward the glacier, what conclusions can you expect to make about the moraines?
The moraines get younger as you get closer to the glacier.
What is the best way to describe the shape of a glacial valley?
U-shaped
In the desert environment, how are ventifacts created?
Ventifacts are produced on the surface of a rock by the continued impact of very small particles carried by the wind.
What is the most important erosional agent in deserts?
Water
Which of the following statements about deserts is true?
Water is the most significant agent of erosion in deserts.
Most of the erosion that took place during the "Dust Bowl" years of the 1930s in the Great Plains of North America was the result of which of the following processes?
Wind
Which of the following is the least effective agent of erosion?
Wind
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.
When a valley glacier leaves the mountains and enters the relative flat lands below, it may spread out to form ___.
a piedmont glacier
Where is the focal point of a glacier's growth?
in a cirque
What is the name used for random boulders left behind by a glacier?
erratics
What is the name used for steep-sided inlets of the sea created when a glacial valley was flooded as sea level rose?
fjord
What do we call this "U-shaped valley which was created by an alpine glacier?
glacial trough
What is the name used for pyramid-like peaks sculpted by valley glaciers?
horns