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GLACIAL FEATURES

​(Arete, Cirque, Esker, Moraine, Glacial Striations, U-Shaped Valley, Till, Braided Stream)​

ARETE

 

DESCRIPTION: An Arete is a sharp-crested serrate ridge that separates two U-shaped glacially carved valleys.

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Figure 1- Aretes on either side of a U-shaped (hanging) Valley. Glacier N.P.

CIRQUE

 

DESCRIPTION: A Cirque is an amphitheater-like basin found at the head of a U-shaped glacial valley that is separated on both sides by aretes.

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ESKERS

DESCRIPTION:  An Esker is a long winding ridge of stratified sand and gravel deposited underneath or within a glacier by a stream of meltwater.

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Figure 1 -  Esker at Wolf Creek Campsite, Whitehorse, Yukon.

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Figure 2 - Esker at Wolf Creek Campsite, Whitehorse, Yukon, illustrating the stratified layers of gravel and sand deposited by glacial meltwater underneath or within a glacier.

 MORAINES (TERMINAL & LATERAL)

DESCRIPTIONS: Moraines are accumulations of unstratified glacial debris

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Figure 1 - Terminal Moraine. Athabasca Glacier. Jasper National Park, Canada.

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Figure 2 - Lateral Moraine. Athabasca Glacier. Jasper N.P., Canada.

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Figure 3 - Terminal Moraine on Long Island. NY.  The Till in the bottom of the photo below is covered by Stratified Drift above as the glacier terminated its southern advance and began to recede northward leaving behind what is now Long Island,

GLACIAL STRIATIONS

DESCRIPTION:  Glacial Striations are smooth grooves in the rock found directly beneath the glacier caused by the abrasion of rock particles within the base of the advancing glacier.  They are exposed after the glacier has receded.

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Figure 1 - Glacial Striations. Northwest New York State.

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Figure 2  - Glacial Striations. Central Park, New York City.

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Figure 3 - Glacial Striations. Near Athabasca Glacier. Jasper National Park, Canada.

U-SHAPED VALLEY

DESCRIPTION: A U-Shaped Valley is one scoured by a glacier, forming a U-shaped cross-section.

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Figure 1 - Glacier National Park, MT.

 

TILL/TILLITE

 

DESCRIPTION: Till is unsorted glacial sediment. Where the till has become lithified by burial, is is referred to as Tillite

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Figure 1 - The hardened layer of Till that appears to have been squeezed between stratified layers has been described as an Injected Tillite. Northwest NY State. (Photo 1976)

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Figure 2 -  Glacial Till overlain by Stratified Drift (Outwash Plain deposits laid down by streams flowing from melting glaciers. Long Island East End. (Photo 1974)

BRAIDED STREAM

 

DESCRIPTION: A Braided Stream is a network of  river/stream channels separated by islands (braid bars). They are commonly associated with high sediment loads and/or coarse-grained sediments such as might be found with glacial meltwaters.

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Figure 1 - Braided streams.  South Alaska.

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