Order of several hundreds to hundreds to tens of

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order of several hundreds to hundreds to tens of thousands of years (shorter term  fluctuations in climate) These climatic variations are due to two major processes Longer term fluctuations in climate due to plate tectonics  Shorter term fluctuations in climate due to variations in earth’s orbit and rotational axis  with respect to sun (Milankovitch cycles) Plate Tectonics—Long term fluctuations in Climate Plate tectonics working model based on two fundamental principles:  Outer shell of earth is divided into a series of 12 or so individual lithospheric plates These plates are in motion with respect to one anther (relative motion) and with respect  to the underlying lower mantle (absolute motion) Plate move at velocities of 2-16 cm/yr as fast your fingernails grow The movements of plates and their interactions can dramatically influence climate— movements occur slowly (cm’s/yr) but over long periods of time (hundreds of millions of  years) can have major impact on climate—bring about changes into/out of ice ages EX—plate tectonics leading to onset of Pleistocene ice age
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Plate tectonic events leading to Pleistocene Ice Age About 70 millions years ago (Late Cretaceous Period) note that South America is  joined  to Antarctica and Australia is joined to Antarctica Because South America and Australia joined to Antarctica no circumpolar ocean  circulation around Antarctica
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