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Physical Earth

Earth's climate has warmed, its sea levels have risen, ice masses have diminished, precipitation patterns have shifted, and acidity and salinity of bodies of water have increased, atmospheric circulation patterns are more variable, and global chemical cycles have changed.

Easton Glacier on Mt. Baker, Washington in 2003. The red line marks the extent of the glacier in 1985.

Mauri S. Pelto, Nichols College

 Land

 Water

 Atmosphere

 Global Cycles

 Disasters

 

 

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    Average global temperatures are anticipated to warm by somewhere between 1.5°C and 6.8°C from 2000 to 2100, depending on human activities . These changes will not be... More »

  • Limestone Featured Article Limestone Limestone

      Limestone  is a sedimentary rock whose chief mineral component is calcite (calcium carbonate: CaCO3). Limestone can be formed by precipitation of calcite... More »

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Limestone Last Updated on 2010-08-08 00:00:00   Limestone  is a sedimentary rock whose chief mineral component is calcite (calcium carbonate: CaCO3). Limestone can be formed by precipitation of calcite dissolved in water or by depostion of marine organisms and entrainment of secondary minerals. Approximately 80 to 90% of limestone composition are skeletal fragments of marine organisms such as coral or foraminifera.  Some other carbonate grains comprising limestones are soil types such as ooids, peloids, intraclasts, and extraclasts; moreover, certain limestones do not consist of grains at all, but rather and are formed completely by the chemical precipitation of calcite or aragonite, the latter also known as travertine. Due to the ease of dissolution and precipitation processes of calcium carbonate, limestone occurrences are linked to fascinating topographic phenomena of cave, karst and limestone... More »