Pleistocene Glaciation of North America

1
Pleistocene Glaciation of North America
2
Pleistocene Ice Ages
3
Direct Effects of Past Glaciation

• Most of the soil and sedimentary rocks were
  scraped off of underlying crystalline rock in
  northern and eastern Canada
• Future lake basins were gouged out of the bedrock
• Extensive sets of recessional moraines were left
  behind by retreating ice sheets in the upper
  midwestern U.S. and in Canada

4
Indirect Effects of Past Glaciation

• Large pluvial lakes (formed in a period of
  abundant rainfall) existed in closed basins in
  Utah, Nevada and eastern California
• Great Salt Lake is a remnant of the much larger
  pluvial Lake Bonneville
• Huge floods emanated as ice-dammed lakes (e.g.,
  Lake Missoula) drained catastrophically
• Sea level was significantly lowered by large
  amounts of water locked up into ice sheets,
  allowing stream channels and glaciers to erode
  valleys below present-day sea level

Giant gravel ripples formed during draining of
Lake Missoula
5
Ice Ages in North America
Continental Glaciers advanced Receded at least
4 times during past 2 million years During
glacial advances, sea level drops exposing
continental shelf Maximum advance of last glacier
18,000 yrs ago Sea level rises 300 ft by 8,000
yrs, resulting in present coastline
6
Evidence of Glaciation in the U.S.
7
End Moraines in the Contiguous United States and
Canada
8
Fjiords
Coastal inlets formed by drowning of glacially
carved valleys by rising sea level
9
The Great Lakes
10
Origin as Meltwater Lakes
11
NY States Finger Lakes
12
Kettle Lakes
13
Ice Lobes in New York State
14
Retreat of the Wisconsinan Glacier

1. Maximum extent of ice about 21,750 years ago
2. 14,000 years ago retreating glacier
3. 12,000 13,000 years ago

15
Retreat of the Wisconsinan Glacier

• Stages D, E, and F occurred 11,000 to 12,000
  years ago
• The final stage was approximately 11,000 years ago

16
Long Island Glaciation
17
Continental Glaciers Retreat forming Long Island
of Today

• Lakes form as ice sheet melts
• Sea Level Rises
• LI Sound fills with water from Ocean
• LI takes modern form
• (from Newsday Long Island Our Story

18
Major Landforms of Long Island
19
Long Island Moraines
20
Topography of Long Island
North Shore Irregular Coast Hilly South Shore
Straight Coast Flat Digital Elevation Model 2X
Vertical Exaggeration (Bennington, 2003) Data
from NYSDEC Cornell University
21
Glacial Features of LI
Lake Ronkonkoma
Harbor Hill Moraine
Ronkonkoma Moraine
Outwash Plain
Kames
22
Glacial Till
Eroding moraine at Montauk

• Unsorted Sediments were deposited directly by
  ice.
• Round shape of many boulders indicates that they
  were also shaped by running water

Boulders at Orient
23
Glacial Features of Smithtown Central LI
Harbor Hill Moraine
Ronkonkoma Moraine
Lake Ronkonkoma
Outwash Plain
24
Harbor Hill Moraine
Closeup view of Till of Harbor Hill Moraine
consisting of unsorted silt, sand, pebbles, and
cobbles
Till of Harbor Hill Moraine overlying outwash
deposits (RTE 25 A, Setauket)
25
Kame Deltas indicate large pro-glacial lakes as
continental glacier melted
Harbor Hill Moraine
Kame Deltas
Ronkonkoma Moraine
Outwash Plain
Note Kame Deltas overlie Ronkonkoma Moraine
What does this indicate about the relative age
of the Deltas?
26
Glacial Features of Huntington Area
Delta Deposits
Harbor Hills Moraine
Outwash Channels
Outwash Plain
27
Delta Deposits at Caumsett

• The sediments in the cliffs formed when streams
  of water carrying sand and gravel gushed from the
  glacier and entered the lake. The faster the
  water the larger size sand grains, pebbles or
  boulders it can carry. Upon reaching the still
  water, the streams slowed and dropped their
  sediments forming a delta.

28
Weathering breaks rocks down Erosion wears away
land transports sediments
Frost Action split this rock
Erosion of bluffs at Caumsett, forming fan
29
Rivers Erode the Land
Smithtown Harbor
Carmans River
Nissequogue River
Ronkonkoma Moraine
30
Carmans River
Carmans River cuts through the Ronkonkoma
Moraine.