UNDERC INTRODUCTION #1:A REGION SHAPED BY

GLACIERS

MULTIPLE PERIODS OFGLACIATION

PLEISTOCENE: 2 million years ago – 10,000 years ago4 major glaciations in North America (~ 14 advances and retreats in last 1 million years)

(However, probably continental glaciations for the past 10 million years)

WHAT CAUSES GLACIATION?• Snows did not melt in northern regions during summer

• 4 – 7oC decline in mean annual temperature (change in δ18O)

Pleistocene

Laurentide

WHAT CAUSES GLACIATION?• Sea-level fluctuates as water forms glaciers

• Gravitational effects of planetary bodies perturb Earth’s orbit which varies distribution of solar radiation (Milankovitch Cycles)

MOST RECENT GLACIAL EXTENT

Extent of Continental Glaciation

•Churchill

•Winnipeg OttawaQuebec

New YorkCleveland

ChicagoSt. Paul

St. Louis•Denver•San Francisco

•Seattle Calgary

•Juneau

•Anchorage

GLACIAL ADVANCE AND RETREAT

(Wisconsin Glaciation – Laurentide

Flowing crystals

Compressed crystals

Ice crystals

New snow

Glacier Cross Section

Inland Lakes Resultingfrom Melt Water

•Churchill

•Winnipeg OttawaQuebec

New York

ClevelandChicago

St. Paul

St. Louis•Denver•San Francisco

•SeattleCalgary

•Juneau

•Anchorage

Miami

Formation of Kettle lakes

Ice Lake

Lake in irregular ground moraine

Kettle in drift

Kettle lake at ice contact on

terminal moraine Kettle lakes in outwash plain

ContinentalGlacier

Ice margin Ice blocks in outwash plain

Formation of Permafrost Lakes

Permafrost No Permafrost

Arctic Permafrost Lakes(Tundra, Northwest Territories, Canada)

Land O’ Lakes Aquatic HabitatsAre Glacial Products

Bay

Long

Bergner

• 35 lakes and bogs• 2 streams• many forest and

wetland habitats

TERRESTRIAL REMNANTS• Glacial drift (deposits of earth and rock)

till = ice-laid outwash = water-laid

• Moraines (till deposited in ridges)

TERRESTRIAL REMNANTS

ERRATICS:

STRIATIONS:

TERRESTRIAL REMNANTS

ESKER – subglacial streams that deposited gravel to now appear as a low winding ridge.

GLACIAL ENVIRONMENTS

HOW ARE ENVIRONMENTS RECONSTRUCTED?

TODAY’S ENVIRONMENT

HOW DID THINGS CHANGE?

Pollen Viewer

Mix Of Different Tree Species Since Glaciation

Disequilibrium View of Forests Since Glaciation

Dissimilarity in Tree

Composition and Climate

CHANGE CONTINUES• EVOLUTIONARY AND GEOLOGICAL CHANGE (inherent)

• ECOLOGY OF AQUATIC HABITATS (inherent)

• ECOLOGY OF TERRESTRIAL HABITATS (inherent)

• HISTORICAL CHANGES WITH HUMANS(Native Americans and Europeans) – environmental history