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UNDERC INTRODUCTION #1: A REGION SHAPED BY GLACIERS. MULTIPLE PERIODS OF GLACIATION. PLEISTOCENE: 2 million years ago – 10,000 years ago 4 major glaciations in North America (~ 14 advances and retreats in last 1 million years)
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MULTIPLE PERIODS OFGLACIATION PLEISTOCENE: 2 million years ago – 10,000 years ago 4 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)
Extent of Continental Glaciation • Anchorage • Juneau • Churchill Calgary Quebec • Seattle • Winnipeg Ottawa New York St. Paul Cleveland Chicago • San Francisco • Denver St. Louis
GLACIAL ADVANCE AND RETREAT(Wisconsin Glaciation – Laurentide
Glacier Cross Section New snow Ice crystals Compressed crystals Flowing crystals
Inland Lakes Resultingfrom Melt Water • Anchorage • Juneau • Churchill Quebec Calgary Ottawa • Seattle • Winnipeg New York St. Paul Cleveland Chicago • San Francisco • Denver St. Louis Miami
Formation of Kettle lakes Ice margin Ice blocks in outwash plain Continental Glacier Kettle lake at ice contact on terminal moraine Lake in irregular ground moraine Kettle lakes in outwash plain Kettle in drift Ice Lake
Formation of Permafrost Lakes Permafrost No Permafrost
Arctic Permafrost Lakes(Tundra, Northwest Territories, Canada)
Land O’ Lakes Aquatic HabitatsAre Glacial Products • 35 lakes and bogs • 2 streams • many forest and wetland habitats Bergner Bay Long
TERRESTRIAL REMNANTS • Glacial drift (deposits of earth and rock) till = ice-laid outwash = water-laid • Moraines (till deposited in ridges)
ERRATICS: STRIATIONS: TERRESTRIAL REMNANTS
TERRESTRIAL REMNANTS ESKER – subglacial streams that deposited gravel to now appear as a low winding ridge.
HOW DID THINGS CHANGE? Pollen Viewer
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