Dating of speleothems

A homogeneous, fine yellow soil covered more than one million square miles of Europe, Asia, and North America.The soil was as thick as 3 meters (10 feet) in some places, and nearly nonexistent in others.

Uranium from the surrounding bedrock seeps into the water and forms a carbonate that becomes part of each layer of the speleothem as it forms.

Uranium decays into thorium, which sticks to the clay in the bedrock instead of seeping into ground water and from there into the speleothem.

Geologists refer to the mineral formations in caves as “speleothems.” While the water flows, the speleothems grow in thin, shiny layers.

The amount of growth is an indicator of how much ground water dripped into the cave.

Loess deposits, composed of fine wind-blown dust produced by the grinding action of glaciers, indicate the former presence of ice sheets in locations around the Northern Hemisphere.

This exposure of loess is near Palouse, Washington. Schwert, North Dakota State University) The story of glaciation and climate change may have been etched into rocks and brushed from the soil like a giant sand painting, but then Nature left the book out in the open.

Exposed to erosion and weathering for thousands, even millions of years, some parts of the original story have been revised or become difficult to read.

Buried in the Earth, however, is another version of the Earth’s climate story, and scientists have begun to leaf through its pages.

However, the reservoir effect may be of minor importance when compared to contamination with younger carbon.

by Holli Riebeek · design by Robert Simmon · June 28, 2005 The first pieces of evidence for climate change came from the land itself, from the misplaced boulders scattered across much of the Northern Hemisphere, though there were other signs as well.

When water levels dropped, the dust blew across the land, leaving an uneven layer of fine, homogeneous soil.

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