Carbon Dioxide from Rise of Appalachian Mountains Caused Global Cooling Long Ago
06.11.2006 - Other
The rise of the Appalachian Mountains may have caused a major ice age approximately 450 million years ago, an Ohio State University study has found. Seth Young, a doctoral student in earth sciences at Ohio State, reported the new study October 25 at the Geological Society of America meeting in Philadelphia.
They've now analyzed quartz sandstone deposits in Nevada and two sites in Europe, comparing the ratio of two isotopes of the element strontium, strontium-87 and strontium-86. They found that, immediately prior to the time that the Ordovician ice age began, the strontium ratio dropped dramatically. The likely cause: a vast amount of volcanic rock was being eroded away, and the resulting sediment was being deposited in the world oceans. The chemical reaction that weathered away part of the Appalachians would have consumed large amounts of CO2 from the atmosphere, right around the time that the Ordovician ice age began.
The Ordovician period started out warm, with high sea levels worldwide. It ended cold, with low sea levels as glaciers covered the poles and portions of the continents. According to the Ohio State study, most of the Appalachian weathering took place over 7 or 8 million years -a very short time, by geological standards- as the climate moved from one extreme to the next - possibly as a result of significant falls in CO2 levels.
