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A Journey to a New Land

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Secondary Level Resources

Glaciation and Sea Level Change

A major consequence of glaciation is its effect on sea levels. Several factors related to glaciation can influence sea levels on either a global or a local scale.

Eustatic sea level change represents a global adjustment in the total volume of sea water contained within the oceans' basins. Under normal climatic conditions, water evaporates from the oceans and is transported and deposited over the Earth's land masses in some form of precipitation. Over time this precipitation makes its way back to the oceans. This process is known as the hydrologic cycle. During periods of glaciation, precipitation becomes trapped in glaciers, preventing it from replenishing the Earth's oceans. This results in a global, or eustatic, drop in sea level.

Isostatic sea level change results from either the depression or uplift of the Earth's crust. Isostatic depression is caused by the loading of the Earth's crust in a localized area. During glacial periods, ice accumulates over a given area and its weight pushes down on the crust, causing the lowering of the land relative to sea level. Isostatic uplift is caused by a reduction of weight on a given area of the Earth's crust, resulting in the rebounding of the land.

Sea level change caused by tectonic factors is the most geographically restricted of these three factors and occurs in seismically-active regions. Due to the mechanics of plate tectonics, stress builds along convergent or transverse plate margins until it is released through the slippage of one crustal block relative to the other along a fault line. This can result in either raised shorelines or drowned beaches.

Glacial recession simulation

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QuickTime videos:

Dr. Michael Wilson

Dr. Michael Wilson
Geology Department
Douglas College

Peter Locher

Peter Locher
Department of Archaeology
Simon Fraser University

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