Lecture 9 - Earths atmosphere is divided into layers on the...

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Lecture 9 (9/8/10) Chapter 5 Early Earth Age of Earth~4.5 Billion years Early Earth- a barren world like the Moon - Lacked oceans - Lacked atmosphere Over time Earth heated up - Meteorite impacts - Compression - Radioactive decay Subsequent melting caused segregation of lighter and heavier minerals Differentiated into 3 major compositional zone - Asthenosphere= weak and soft mantle - Mantle - Core(inner & outer) - Figure 5-2 Development of the Atmosphere The atmosphere developed between 4 and 3.5 billion years ago Since that time, the oxygen in the atmosphere has increased considerably due to photosynthesis - The breakdown of water by ultraviolet radiation
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- Photosynthetic organisms Earth’s Present-Day Atmosphere
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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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Lecture 9 - Earths atmosphere is divided into layers on the...

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