glacial environment

Glacial Environment

Every thing starting as a Snow Flake and snow flake is a beautiful hexagonal crystal of ice

Formation of snowflakes

Formation of snowflakes

As the snow accumulates, it is gradually transformed into ice. The weight of overlying snow packs it down, drives out much of the air, and causes it to recrystallize into a coarser, denser form (Firn) an intermediate texture between snow and ice, and finally to a compact solid mass of interlocking ice crystals

This process may take a few seasons or several thousand years, depending on such factors as climate and the rate of snow accumulation at the top of the pile

Glaciers

A large mass of moving ice Capable of eroding, moving, and depositing large amounts of material.

Types

Mountain or Alpine glaciers :Forms over the mountains and the ice start flowing down to form valleys

Once formed, the weight of snow accumulating in the upper part of the glacier causes it to move downslope, where it reaches lower altitudes and higher temperatures. The lower part of the glacier is the ablation zone where the glacier melts during the summer.

Under stable climatic conditions equilibrium develops between accumulation at the head and melting at the front, with the glacier moving downslope all the time, but the positions of the head and snout remain fixed

Zone of accumulation (input)Zone of ablation (ablation exceeds accumulation)

Continental glaciers

Much larger and thicker forming massive sheets of ice2 polar ice sheetsGreenlandAntarctica

Ice sheetExtends over 50,000 km2

Antarctic and Greenland

Ice capSimilar to an ice sheet though smallerForming roughly circular, dome-like structure

Continental glaciers

Glaciers do not behave as rigid, Their flow is plasticHigh pressure and some times geothermal heat causing in melting of the layer at the base so ice start sliding Move by two basic processes:

Basal Slip – the process causing the ice at the base of a glacier to melt and the glacier to slide.

Internal Plastic Flow(internal deformation) –the process by which glaciers flow slowly as grains of ice deform under pressure and slide over each other.

Movement

Internal deformation

Glacial advancing

When accumulation rate exceeds ablation rate so we have glacial advancing

Glacial Retreating

When accumulation rate less than ablation rate we have glacial retreating

GLACIAL EROSION

Mechanism involved…PluckingGlacier flows over a fractured bedrock surfaceit loosens and lift blocks of rocks and incorporate them into ice

Notice that this process seasonable and image just for clarifying

AbrasionHappens when ice and its load of rock fragment slides over bedrock

Plucking and abrasion

Freeze Thaw

The glacial processes that change the shape of mountains begin in the upper end of the valley where

an alpine glacier forms.

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How selected features of continental glaciation, including kames, originated.

During Glacial Cirque and Arêtes form and glacial creates a U shaped valley

Postglacial

Features of alpine Glaciation

Erosional features CirquesArêtesHornsTruncated spursU-shaped valleysHanging valleysTarns and paternoster lakesDepositional FeaturesMoraines

Cirque formation

An arête is a sharp ridge formed when two cirques cut back

Arête

Features of alpine Glaciation

a)Horn( b)Cirque (c)Arete

a)Horn (b)cirque (c) U shape valley

a

b

c

a)Horn (b)cirque(c)arete (d)truncated spurs

a

aa

b bb

cc

d

b

U shape valley after glaciation

Hanging valley

Tarn

Paternoster lakes

Glacial Deposition

Landforms resulting from a glacier depositing till are called moraines.

Lateral moraine: deposited along the sides of an alpine glacier, usually as a long ridge.

Medial moraine: form when the lateral moraines of alpine glaciers meet.

Ground moraine: unsorted materials left beneath the glacier when the ice melts.

Terminal moraine: small ridges of till deposited at the leading edge of a melting glacier.

Ground Morains

Erosional features

roche moutonnée

Depositional features

Terminal moraines

Till plain, outwash plain

Eskers

Kettles

Kames

Erratics

Drumlins

Features of Continental Glaciation

Roche moutonnée

Roche moutonnée (sheepbacks)

Ice flow

Stoss sideLee side

51

How selected features of continental glaciation, including kames, originated.

Eskers

Melt water forms a tunnel under a glacial ice sheetTunnel fills with rocks, sand and gravel

After retreat of the ice, material collected in the tunnel is left to form a ridge

Kettle lake

A big chunk of ice trapped then melted to form kettle lake and sediments deposited around it

Erratics

Large rocks transported from a distant source by a glacier

Erratics

Erratics

Deposition: drumlins

Oval shaped hills

Formed of till left by glaciation

Blunt end facing opposite ice flow

Often found in “shoals”

Drumlins

Ice flow

Eskers – economic benefits

Mined for materials – sand, gravel and stones for construction

Used for natural water filtration

Glaciers are not only large masses of ice; they can also be viewed as an important freshwater reserve. Approximately 75% of the fresh

water on earth is stored as ice in glaciers

Important source for deposits

Climate and environment indicator

General Benefits

Glacial Geology, Ice Sheets and Landforms [Matthew M. Bennett, Neil F. Glasser]

Sedimentologyandstratigraphy 2nd edition by Gary Nichols

Environmental geology , carla c montgomry

Further reading

Regards,AmrElgabry