Lecture 27 more glaciers

dropped when ice melts.Unstratifed drift: glaciers Called Till or tillite Stratified drift: melt water streams or lakes.. 22.22 cCourtesy Duncan Heron Stratified glacial Lake deposits..

Chapter 12: Glaciers & glaciation

Chapter 12: Glaciers & glaciation

Today:

dropped when ice melts.

Unstratifed drift: glaciers

(Called Till or tillite)

Stratified drift: melt water streams

or lakes.

(Example: Glacial varves)

Deposited by

Fig 22.21 c

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Glacial deposits are called drift…

Fig 22.22 a

Stephen Marshak

Unstratified glacial drift is called till…

Glacial Erratic

Fig 22.22 c

Courtesy Duncan Heron

Stratified glacial Lake deposits

Fine grained glacial material (rock flour) redistributed by

the wind.

Fig 22.14

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How to find a meteorite…

Glacial deposits

recessional moraine: a series of terminal moraines

formed when a glacier recedes in steps.

ground moraine: blanket of till left when

a glacier retreats rapidly.

lateral moraine: till deposited along the side of glacier medial moraine: formed where two or more

glaciers merge.

Glacial deposits

formed along margins of glacier.

Fig 22.21 a

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Glacial deposits

Unstratified drift ● Moraines

End moraine: ridge of till at end of stable glacier Recessional moraine: all other end moraines

Fig 22.23 b

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Fig 22.24

W W Norton Adapted from Tarbuck and Lutgens, 1996

Glacial deposits

Stratified drift: ● outwash plains

● kettle lakes

● eskers

Fig 22.26 a

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Kettle lakes…

Fig 22.26 b

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Glacial deposits

Stratified drift landforms ● outwash plains

● kettle lakes

● eskers

Fig 22.23 a

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Fig 22.27

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Glacial deposits Till landforms ● Drumlins Smooth elongated parallel hills

Fig 22.25 a

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Glacial deposits Till landforms ● Drumlins Smooth elongated parallel hills

Glacial deposits

GLACIERS

Till landforms ● Drumlins Smooth elongated parallel hills

Glacial deposits

GLACIERS

Till landforms ● Drumlins Smooth elongated parallel hills

Fig 22.25 c

Fig 22.35 a

Fig 22.35 b

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Effects of Continental Glaciation

Ice retreat/advances:

Animal/plant distribution change,

extinctions ensue with climate

Global Sea Level Changes

Sea level changes

If all Earth’s ice melted:

Causes of Glaciation

● Ancient Ice Ages 2 billion years ago

600 million years ago

250 million years ago

Fig 22.36 a

Modified from Skinner and Porter,

1995

Fig 22.36 b

Modified from Skinner and Porter,

1995

Fig 22.30 a1

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Fig 22.30 a2

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Fig 22.30 a3

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Causes of Ice Ages

● Earth orbit variations

Shape of orbit (more elliptical)

changes in tilt of rotation axis

wobbling of axis

Milankovitch Cycles

● Variations in the Earth’s orbit

and distance from the Sun.

Shape of orbit (more elliptical)

Changes in tilt of rotation axis

Wobble of axis

Fig 22.41 a

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Fig 22.41 b

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Fig 22.41 c

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Fig 22.41 d

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