Glacier questions

Question 1

Explain the term dynamic equilibrium.

Answer 1

Dynamic equilibrium is a state of balance between opposing forces, such as erosion and deposition, in a system. In a glacier, dynamic equilibrium is when the rate of accumulation of snow and ice at the upper reaches of the glacier is equal to the rate of melting and ablation at the lower reaches.

Question 2

Describe the flows of energy and material through glaciated systems.

Answer 2

Glaciers are important systems for the transfer of energy and material from the atmosphere to the environment.

The energy input to the glacier comes from the sun, converted to heat energy and melting.

This melting water then provides a source of water to the surrounding environment, as well as a source of material in the form of sediment.

As the glacier moves, it carries sediment and material with it, resulting in the formation of moraines and other landforms.

The energy and material flows are also important for the health of the glacier, as they help to maintain the dynamic equilibrium of the system.

Question 3

Explain the process of nivation

Answer 3

Nivation is a collection of processes which expand the formation of a corrie, the base of the glacier, through the repeated process of freezing and thawing and removal of material by melting snow, causing a hollow to form into a cirque.

Question 4

Explain the process of regelation

Answer 4

Regelation is the melting of ice under pressure, normally caused when the glacier meets a ridge or object in its way, causing the ice at the underlying layer of the glacier to melt under the pressure of the ice above it, allowing it to move around the ridge / object, and then re-freeze after the pressure is released / under lower pressure, creating a new layer of ice which can help stabilise the glacier.

Question 5

Corries

Answer 5

Armchair shaped hollows created by nivation, plucking and glacial erosion found on the side of a mountain.

Question 6

Arêtes - Erosional

Answer 6

Narrow, steep sided ridges of resistant rock found on either side of corries. Formed due to the erosion of corries, which includes nivation and plucking.

Question 7

Pyramidal peak - Erosional

Answer 7

The steep, pointed mountain peak carved out by the existence of corries on its mountainside.

Question 8

Roches Mountoneés - Erosional

Answer 8

An extrusion of resistant rock found on the valley floor which has been caused by the glacial erosion of the rock surrounding it. The Roches Mountoneés itself has been plucked on its face that faces away from the glacial flow, as regelation causes the ice to melt under pressure, which then seeps into the back wall of the RM and therefore causes plucking.

Question 9

Striations - Erosional

Answer 9

Striations are deep scratches and grooves in the valley sides / floors, caused by abrasion, which is due to deposition carried by the glacier coming into contact with the less resistant valley floor / sides.

Question 10

Ellipsoidal basins - erosional

Answer 10

Ellipsoidal basins are caused when ice caps erode large amounts of land, leaving a shallow basin in the shape of an ellipse. The weight of the ice cap also compresses the land underneath it, creating the basin in addition to the erosion.

Question 11

Terminal moraines

Answer 11

Terminal moraines are pro-glacial moraines (crescent - shaped mounds of glacial deposit) which have been left at the furthest point the glacier ever reached.

Question 12

Recessional moraines

Answer 12

Recessional moraines are pro-glacial moraines (crescent - shaped mounds of glacial deposit) which can be found in between a terminal moraine and glacier, signifying a glaciers growth and retreat after reaching its maximum point, at which the terminal moraine can be found.

Question 13

Lateral moraine

Answer 13

Lateral moraines are moraines which can be found on either side of the glacier.

Question 14

Medial moraines

Answer 14

Where two lateral moraines combine, separating two glaciers which are moving in the same direction.

Question 15

Erratics

Answer 15

Resistant rock that was deposited onto the glacier or plucked from an area of less resistant rock, which is then transported with the glacier until the glacier recedes, running out of energy and the erratic is deposited.

Question 16

Drumlins

Answer 16

Drumlins are elongated, oval-shaped hills which form when a glacier moves over a ridge / mound of more resistant rock, leaving its deposits on the other side, forming a mound:

“Drumlins may have formed by a successive build of sediment to create the hill (ie deposition or accretion) or pre-existing sediments may have been depleted in places leaving residual hills (ie erosion), or possibly a process that blurs these distinctions.”

Question 17

Till sheets

Answer 17

Large, thick masses of unstratified till forming extensive, flat surface, found pro-glacially. Till sheets is a landform found once the glacier has retreated at the end of a glacial period, leaving till behind.

Question 18

Delta Kames

Answer 18

A stratified and sorted mound of sediment caused by:

Either:

Englacial streams running under pressure carrying sediment; They loose energy when they appear out the ‘snout’ of the glacier and deposit their load at it’s base.

Or

Supra-glacial streams carrying sediment which looses its energy once it reaches the end of the glacier and meeting a static body of water, such as a proglacial lake.

Question 19

Kame Terraces

Answer 19

Kame Terraces are also stratified and sorted sediment, however, form ridges found on the valley floor on either side of the glacier near the valley wall.

Caused by Supra-glacial streams near the valley wall, caused by the melting of ice near the valley wall (under pressure or due to the warmer valley sides) picking up lateral moraine which is later deposited once the glacier retreats.

Question 20

Eskers

Answer 20

A stratified, sinuous ridge of sediment found at the base of the glacier on the valley floor.

Formed when sub-glacial streams, which carry sediment under pressure (due to the weight of the glacier above it) drop their loads once the glacier retreats, as the streams loose pressure, forming long ridges of stratified till, which can measured in width / length and also be ‘beaded’, these factors show the rate at which the glaciers melted at / seasonal deposition rates.

Question 21

Outwash plains

Answer 21

An Outwash plain AKA Sandhur, is a vast expanse of sediment found pro-glacially