Transcript Glaciers: Part 1

Mysterious rock
formations…….
What could have caused
these formations?
GLACIERS!!!!!
Evidence for Glaciers
Erratics
Unsorted
material
Striations
Polished
Bedrock
Erratic
Erratic
Boulder-sized rock
dumped by a
glacier
 Rock is different
type than
surrounding rocks

Unsorted
Materialsall sizes
mixed
together.
Striations
Chatter marks
(Maine)
Striations/ Chatter marks
Grooves carved
into bedrock
 Formed by
abrasive action of
cobbles and
pebbles carried at
bottom of glacier
 Direction of
scratches shows
direction glacier
moved

Glacial polish
Smooth rock
surfaces
 Created as glaciers
flow over bedrock

Glacial Pavement….
What does a glacier look like?
What conditions are necessary for
glacial formation?
Cold
Summers!!
Located above the snow line, or in
polar regions.
Presently occupy 10 % of world’s total
land area (32% during ICE AGES)
Form on all continents BUT Australia
Process of Glacier Formation
 Snow
does NOT melt in summer
 Recrystallization of snow to form LARGE
crystals of ice (rough and granular)
–called FIRN: liked packed snowballs
 Lower layers turn to SOLID ICE under the
weight of overlying firn and snow.
Snow becomes Firn
Glaciers: Types

VALLEY GLACIERS:
long, slow-moving,
wedge-shaped
streams of ice
Bordered by
mountains

Size varies*


small= 1-2 km long, 100’s m wide, 100’s m
deep*
largest = Over 100km’s long X 100’s m deep
 CONTINENTAL
GLACIER (ICE
SHEETS):
 very old (1000’s of years) and thick
(1000’s of meters)
Not confined by mountains

Examples:
GREENLAND: 1.7 million square miles, 2
miles thick
ANTARCTICA: 12.5 million square miles, 3
miles thick
Features associated with
valley (alpine) glaciers
Original valley
(V-shaped)
Glaciers come
and alter
landforms
Glaciers retreat
and new
features appear
Landscape FeaturesValley Glaciers

CIRQUES:
 semi-circular shaped bedrock feature
 created as a glacier scours back toward the mountain

ARÊTES:
steep-sided, sharp-edged bedrock ridge
 formed by two glaciers eroding away on
opposite sides of a ridge
TARNS:
glacial lakes
produced by glacial scouring
often found in cirques
CIRQUE
TARN

HORNS:
 3 or more cirques adjacent to one
another
Hanging Valley
ARÊTE
U-SHAPED
VALLEY
CIRQUE
HANGING
VALLEY
U-shaped valley
CONTINENTAL GLACIERS
FEATURES
Lateral moraine
 MORAINES:
material left behind
when glacier recedes
When glacier retreats (melts) rock and
sediments are dropped behind
 Long Island, Cape Cod and the islands are
part of a terminal moraine

Kettle Lake
Drumlins
Esker
Till
Moraine-dammed
lake
Terminal Moraine
Glacial
Stream
Drumlin
drumlins
Kettle Lakes
River in glacier
carries sediment
Glacier melts
Drops sediment
Esker results
Eskers