PLEASE ANSWER BOTH FOR A THUMBS UP. 1. There are less than half as many glaciers
ID: 287094 • Letter: P
Question
PLEASE ANSWER BOTH FOR A THUMBS UP.
1. There are less than half as many glaciers in Glacier National Park as there were 150 years ago. If the glaciers in Glacier National Park all melted away, what sorts of features would they form? Make sure you include at least two specific examples.
2. The land in Kentucky where Mammoth Cave formed consists of a layer of soil on top of a layer of sandstone on top of a layer of limestone. Explain why this structure leads to caves that are not likely to collapse.
Explanation / Answer
1)
A glacier is a large body of ice that forms on land from the compaction and recrystallization of snow and moves downward due to gravity.Glaciers are not landforms. The action of glaciers create landforms by a process known as glaciation. Glacial ice is an active agent of erosion,which is the gradual wearing away of Earth surfaces through the action of wind and water. Glaciers move and as they do, they scour the landscape,carving out landforms.
The downward and outward flow of ice in a glacier behaves like a conveyor belt which serves as a denudational agent. It can erode and deposit sediments.
A glacier erodes in two ways:
Plucking - where the basal ice thaws and refreezes each summer. Surface rocks and soil get frozen onto the bottom of the glacier and transported toward the terminus of the glacier.
Abrasion - where the debris is carried along the base of the flowing ice can gouge out and physically wear down or flatten the terrain it passes over.
The erosional features formed by a glacier are as follows:
a) Cirque
b) Glacial Trough
c) Hanging valley
d) Fjord
e)Arete
f) Horns
Like erosion, glacier also forms certain depositional features like-
Deposition: At the glacier's terminus, ice melt liberates the clasts transported in the ice mass, and they are deposited as two types of glacial sediments namely :
Till - dropped as a pile of glacial debris where the ice melts. This material is poorly sorted, with a mix of many clast sizes.
and Outwash - fans of glacial sediments carried away from the glacial terminus by runoff of glacial meltwater. The other depositional featues that can form are :
Moraines: This is a general term applied to rock fragments, gravel, sand, etc. carried by a glacier and deepending on its position, the moraines can be ground, lateral or terminal/end moraines.
Drumlins: Drumlins are inverted boat-shaped deposition in a till plain caused by glacial deposition.
Kettle holes: It forms when the deposited material in a till plain gets depressed locally and forms a basin.
Outwash plain: When a glacier reaches its lowest point and melts, it leaves behind a stratified deposition material, consisting of rocks, clay, sand, gravel etc and this layered surface is called till plain or an outwash plain.
Hanging valley: It is a ‘U’ Shaped Valley formed at the mature stage of valley formation.
2) In Kentucky, since it is underlain by limestone the area is prone to the formation of sinkholes. A sinkhole is a depression or a hole in the ground caused mainly by the dissolution of carbonate rocks chemically. They are mostly caused by Karst processes. Sinkholes sometimes capture surface drainage from running or standing water. Sinkholes often form through the process of suffosion which is the process in which groundwater dissolves the carbonate cement holding the sandstone particles together carrying away the lax particles, gradually forming a void. Here, since the limestone layer is overlain by a layer of sandstone, suffosion is the probable reason behind the formation of sinkholes. Here in ammoth cave, sometimes a river or a stream or river may be visible flowing underground across its bottom flowing from one side to the other. These sinkholes are not likely to collapse because they are not filled up completely as the flow of groundwater in these aquifers is through the pores in between the grains of sand or through the narrow fractures in the solid bedrock. The small openings act as a filter removing most of the suspended matter, which holds back the soil cover. The movement of water through the fracture system of a fractured bedrock aquifer or the pore spaces of a granular aquifer is slow, when compared to movement in a karst aquifer. Thus the flow velocity in a granular aquifer is too slow, and the pores too small, to transport grains of soil thus taking more time to get filled up.
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