THE ICE AGE

A. INTRODUCTION

Last ice age began ~2.5 MYBP

Image: NOAA Paleoclimatology Program/Department of Commerce

B. GLACIALS AND INTERGLACIALS

Image: Robert A. Rohde, Global Warming Art

Numerous large temperature changes

glacials: cold periods of ice sheet growth

interglacials: warm periods of ice sheet retreat

Evidence

ocean sediment cores: marine oxygen isotope record

ice cores

Events

Wisconsin glacial - most recent; 115,000 YBP - 10,000 YBP

Late Wisconsin - 25,000 YBP - 10,000 YBP

Sangamon interglacial - 130,000 - 115,000 YBP

Illinoian glacial

all earlier glacials/interglacials referred to by their isotope stage

C. POSSIBLE CAUSES OF CLIMATE CHANGE

Plate Tectonics

changing geographic location of the continents

Uplift of the Himalayas

changes in circulation

intensification of Asian monsoon

increased chemical weathering

Changes in Atmospheric Composition

data: Barnola, J.M. D. Raynaud, C. Lorius & N.I. Barkov (2003) Historical CO2 record from the Vostok ice core. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

Astronomical Theory

shape of the earth's orbit

Images: NASA Earth Observatory

tilt of the earth's axis

Image: NASA Earth Observatory

"wobble" of the earth's axis

Image: NASA Earth Observatory

Changes in Ocean Circulation

Image: NASA

D. SUMMARY

climate - externally driven force

drives processes of degradation:

weathering: weakens the resisting framework

water & ice: erode & deposit material, sculpting, and ultimately wearing down the continental surfaces