Chapter 12 Flashcards
What is a glacier?
A large, long lasting mass of ice, formed on land by the compaction and recrystallization of snow, which moves because of its own weight.
What are the two types of glaciers?
Alpine
Continental
What is a valley glacier?
A glacier that forms high up in a valley and flows from top to bottom.
What is an ice sheet?
A glacier covering a large area of land usually more than 50, 000 square kilometers.
What is an ice cap?
A glacier converting a relatively small area of land but not restricted to a valley.
What is ablation?
The loss of the glacial ice or snow by melting evaporation or breaking off into icebergs.
What is an advancing Glacier?
Glacier with a positive budget, so that accumulation results in the lower edges being pushed outward and downward.
What is a receding Glacier?
A glacier with a negative budget, which causes the glacier to grow smaller as its edges melt back.
What is the zone of accumulation?
The top portion of a glacier with a perennial snow cover. Were the glacier grows the most.
What is the zone of ablation
The portion of a glacier in which ice is lost.
What is the line of equalibriam?
The line between the zone of accumulation and ablation
What is the Terminus of a glacier?
The lower edge of a glacier.
What is basal sliding?
Movement in which the entire glacier slides along a single body on its base over the underlying rock.
What is the rigid zone?
The upper part of a glacier in which there is no plastic flow.
What is a crevasses.
Open fissures in a glacier caused by the bending of ice as it goes over steps often hundreds of meters deep.
What is an outlet Glacier?
Where mountain ranges are higher than the ice sheet, the ice flows between mountains as valley glaciers, known as outlet glaciers.
What percentage of the earths surface is covered by glaciers?
10%
What is an icestream?
A zone of ice that has considerably higher flow rate than the adjoining ice.
What are the variables in the movement of a valley glacier down slope?
1: Ice temperature
2: Glacier Thickness
3: Steepness of the slope the glacier is on
What is plucking known as?
When a glacier freezes and cracks the rock underneath and then plucks out the chunks as fragments.
What is striation when referring to glaciers?
The scratch lines of the underlying rock usually smooth. It indicates what direction the ice was flowing.
What is rock flour?
A powder of fine fragments of rock produced by glacial abrasion.
What does a valley in a U shape tell you about the valleys history?
It was formed by Glacial Erosion.
What is a hanging Valley?
A side glacier that did not erode as much as the main glacier leaving an abrupt drop of were the two glaciers met.
What are truncated spurs?
A glacier is to sluggish to make rounded turns so its corners are usually sharp.
What are rock basin lakes?
Lakes that are formed from glaciers flowing down hill and certain parts of the rock being more resistant to erosion than others and steps are formed.
What is a cirque?
A steep-sided amphithere like hollow carved into a mountain at the head of a glacial valley.
What kind of erosion do ice sheets tend to produce?
Rounded topography as well as knogs and occasionally trenches.
What is till?
Unsorted and unlayered rock debris carried by a glacier.
What is an erratic?
An ice-transported boulder that does not derive from bedrock near its present site.
What is moraine
A gody of till either being carried on a glacier or left behind after a glacier has receded.
What is Lateral Moraines
low, ridgelike pile of till along the side of a glacier.
What is end Moraine
Till that is piled up at the the front edge of a glaciers because it has not moved in a long time.
What is commonly produced by the movement of an ice sheet?
Rounded Knobs
Striated Bedrock
Grooved Bedrock
How does an ice sheet round and streamline mountains?
By flowing over a completely covered mountain range.
What is a Medial Moraine
when there are rows of till built up between rows in a glacier.
What are drumlins?
A long, streamlined hill made of till.
What is Outwash?
Material deposited by debris-laden meltwater from a glacier.
What are eskers?
A long, sinuous ridge of sediment deposited by glacial meltwater usually they are streams that existed under a glacier.
What is a kettle?
A depression caused by the melting of a stagnant block of ice that was surrounded by sediment.
What is a varve?
Two thin layers of sediment, one dark and the other light in color, representing one years deposition in a lake.
What is the Theory of Glacial Age?
At times in the past, colder climates prevailed during which significantly more of the land surface of earth was glaciated than at present.
When did the last of the great North American ice sheets melt away from Canada?
Less than 10,000 years ago.
What Epoch is the glacial age associated with?
Pleistocene
What was the largest ice sheet during the glacial age?
The Laurentide Ice Sheet.
What is a pluvial lake?
A lake formed during an earlier time of abundant rainfall.
Fiord
A coastal inlet that is glacially carved valley, the base of which is submerged.
What evidence supports the snowball earth hypothesis?
Tillites deposited at the equator.
Average annual temperatures during the height of a glacial age are about how much cooler than today?
5 Degrees
how old is the oldest glacian that we have evidance for?
2.3 billion.
What are indicators for alpine glaciations being much more extensive throughout the world during the glacial ages than they are now?
1: Cirques and other features typical of valley glaciers are found in places that are no longer glaciated.
2: Small glaciers in the rocky mountains were once several kilometers in length.
What is Louis Agassiz responsible for?
1: Publishing a discourse arguing that switzerland was entirely glaciated in the past
2: concluding that a great glacier had covered most or all of europe.
3: Finding evidence of past glaciation of the british isles
4: Finding similar evidence of past glaciation of North America.
