Glacial Landscapes

what are the similarities between glaciers and streams?

they can flow in channels, they can have tributaries, they can combine to form larger glaciers, and they can flow as a sheet over flat unconfined surface

what is a glacier?

a thick mass of ice that forms by the accumulation, compaction, and recrystallization of snow

where are glaciers formed?

high elevation and/ or high latitudes

what is firn?

an intermediate stage between snow and glacial ice

what is a cirque glacier?

bowl shaped recess at the head of a valley surrounded by mountain walls on three sides

valley glacier

develop when growing cirque glaciers flow into pre-existing steep-walled valleys

what is an ice sheet?

a continuous mass of glacial ice that covers an area of more than 50,000km2

Glacial mass balance

refers to the inputs and outputs and whether or not they are in balance

accumulation zone

the area where glacier ice forms and inputs are greater than outputs. located above the snow line/ equilibrium line

ablation zone

the region where the outputs are greater than the inputs so a net loss of snow and ice

equilibrium line

the elevation line at which accumulation is equal to ablation

when do glaciers advance?

if accumulation exceeds loss; a positive mass balance

when does an ice front retreat?

if ablation exceeds accumulation

what happens when accumulation and ablation are equal?

the glacier does not grow or shrink

internal deformation

movement within the ice

Basal sliding

ice slides over the underlying surface

what enables basal sliding?

meltwater at base of the ice that acts as lubricant enhancing the sliding motion

regelation ice

the melting and refreezing of ice at the bed

where is glacial flow the greatest?

in the center of the glacier

crevasses

fractures in the ice that open and close

what are the two ways that glaciers erode the land?

plucking and abrasion

what is plucking?

glacier flow loosens and lifts rocks from glacier bed occurring when meltwater penetrates the cracks and joints of bedrock beneath the glacier and freezes

glacial abrasion

acts like sandpaper smoothing and polishing underlying rock surfaces

what are the three products of glacial abrasion?

glacial striations, glacial polish, and rock flour

what are glacial striations?

grooves in the bedrock

what is glacial polish?

smoothed shiny bedrock

what is rock flour?

pulverized rock

how do glaciers transform V-shaped valleys into U-shaped glacial troughs?

widening and deepening

how do hanging valleys form?

when the main glacier carves deeper into the landscape than its tributary glaciers, resulting in the tributary troughs being elevated above the main valley floor as the ice melts.

cirque

bowl-shaped depression at the head of a valley surrounded by mountain on three sides

tarn

small lake within a cirque

col

pass between mountain valleys where the headwalls of two cirques intersect

fjord

deep, steep-sided inlets of the sea (drowned glacial troughs formed when the sea level rises)

arete

a narrow sharp-edged ridge separating two glaciated valleys or cirques

horn

pyramid shaped mountain peak surrounded by at least three cirques; matterhorn

roche moutonnee

formed by glacial plucking and glacial abrasion; an asymmetrical hill of exposed bedrock

what is the characteristic of a roche moutonnee?

gently sloping upstream side that is polished smooth and a steep downstream side where the glacier plucked rock pieces

what is the difference between transported sediments in rivers and glaciers?

glaciers do not sort the sediment they transport

till

unsorted, unstratified sediments deposited directly by glacial ice; having a wide range of particle sizes and not deposited in layers

glacial erratics

retreating glaciers leave behind large rocks with different origin than local rocks

what is a moraine?

landform made of glacial til occurring only in mountain valleys that were once glaciated

what are the various types of moraines?

lateral, medial, terminal, ground, and recessional

lateral moraine

an accumulation of rock debris on the side of an alpine glaciers

medial moraine

created when two alpine glaciers converge, causing the lateral moraines to converge in the centre of the new glacier

terminal moraine

eroded debris that is dropped at a glaciers farthest extent; tells geoscientists how large the glacier was

recessional moraine

end moraines formed as the glacier temporarily stabilized during retreat

ground moraine/ til plain

a deposition of til that is generally spread across a surface

outwash plain

broad surfaces of stratified/ layered sand and gravel deposited by glacial meltwater associated with an ice sheet

valley train

broad surfaces of stratified/ layered sand and gravel deposited by glacial meltwater confined to a mountain valley

kettle lakes

form after an isolated block of glacial ice remains in a ground moraine or an outwash plain after a glacier retreated

esker

a sinuous curving, narrow steep-sided ridge of somewhat stratified coarse sand and gravel

drumlines

smooth, streamlined, teardrop-shaped depositional landforms