GLACIERS

What Are Glaciers?

• glaciers are systems of ice originating on land through the accumulation and recrystallization of snow
• 3 types of glaciers
• valley glaciers (alpine)
• originates high on a mountain and moves downward through preexisting valleys
• cirque glaciers are special types of valley glaciers that occupy an erosional feature that is cut into bedrock and is bowl shaped (cirque)

• continental glaciers
• a slow-moving ice sheet that resembles a giant dome several thousand meters thick in the center and sloping down toward sea level on all sides

• piedmont glaciers
• found at the foot of a mountain
• occur when valley glaciers come out of mountains and join at the foot of a mountain

How Do Glaciers Form?

• glaciers form in areas where winter snowfall exceeds summer melting - zone of accumulation
• does not require year-round snowfall, only cold enough to have snow exist through the summer
• the weight of accumulating snow compress lower layers into glacial ice
• snow
• granular ice
• firn
• glacial ice

• as the ice accumulates, it begins to flow

• the glacier also loses ice - zone of ablation
• melting
• calving
• sublimation

Glacial Budgets

• accumulation minus ablation; types
• accumulation < ablation
• accumulation = ablation
• accumulation > ablation

How Do Glaciers Move?

• ice flow due to:
• basal sliding - due to base of glacier being wet
• creep (plastic flow) - due to gravity
• crevasses

• patterns of flow
• valley glaciers vs. continental glaciers

How Do Glaciers Move Sediments?

• very different from any other type of sediment movement
• no differentiation of size of material
• when material is deposited it is unsorted and unstratified
• Glacial Drift: any material that is deposited by glaciers
• till
• stratified drift

The Features of Glacier Systems

• Continental Glaciers
• striations
• erratics
• drumlins
• eskers
• kettle lakes

• moraines
• ground moraine
• terminal (or end) moriane (terminus)
• recessional moraine

• outwash plain

• Valley Glacier
• aretes
• cirque
• horn
• hanging valley
• truncated spurs
• terminus
• moraines
• lateral moraine
• medial moraine

Pleistocene Ice Age (3 million years ago)

• four separate glacial advances

• Holocene Interglacial (current - 10,000)
• Wisconsinan Glaciation (200, 000 -18,000 ya)
• Sangamon Interglacial
• Illinoian Glaciation(550,000 - 400,000 ya)
• Yarmouth Interglacial
• Kansan Glaciation (1,400,000 - 950,000)
• Aftonian Interglacial
• Nebraskan Glaciation (2,200,000 mya - 1,750,000 ya)

Why Did Ice Age Occur?

• the amount of solar energies varies and when the earth moves it gets less energy
• only need to lower temperatures by 6F and we would be in another ice age