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Unformatted text preview: Earths atmosphere is divided into layers on the basis of changing temperature gradients The density of atmospheric gases decreases exponentially going away from the Earths surface 99% of the gases are found in the lower atmosphere-N2=78.1%-O2=20.9% Figure 3-2 & 5.12 Air currents created in lower atmosphere by convection cells Modified by-Coriolois effect-Presence of oceans-Topography of continental land masses Development of the Hydrosphere By about 4 billion years ago, the Earth probably had an ocean The water came from?-Constituent of gas & dust cloud from which the Earth coalesced-Incorporated into mineral structure of rocks-Released as water vapor by volcanic activity-Collision with icy comets...
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- Spring '09