13_Review_Prelim1 - Review for Prelim 1 Origin and Earth...

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1 Review for Prelim 1 Nebula forms out of H, He clouds and fusion products from now dead stars. Gravity pul s gas and dust inward, and rotation makes a accretionary disk. The proto-sun is at the center and fusion begins when it is hot enough. Heavier elements concentrate in the inner rings. Col isions and gravitational attraction leads to the formation of planetesimals. Gravity reshapes the proto-Earth into a sphere Soon after Earth formed, a Mars-size planet col ided with Earth, blasting debris into space that wil form our Moon. Volcanic gases form the atmosphere, and as Earth cools, moisture condenses and rains into oceans. Some gases may have come from passing comets. Summary of Earth-Moon Formation
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2 Early in Earth’s history Today Conditions of Early Earth versus Late Earth Atmosphere consisted of hydrogen and helium - gases abundant in the solar system. Most of these gases were lost to space. Over time out-gassing from volcanoes releases: H 2 0, CO 2 , SO 2 , N 2 , H 2 , Cl 2 Water vapor condensed and precipitated to form oceans and anaerobic Life Develops! Photosynthetic life then evolves and this produces a modern O 2 -rich atmosphere! Two Current Ideas on Origin of Water: (1) Planetisimals that aggragated into Earth contained ice, water and other gases. They were locked in minerals, but escaped as Earth melted during heavy bombardments. (2) Water came from volatile-rich comets that impacted the Earth, which (we know now) consists of water-ice and frozen CO 2 Two Hypotheses for the Origin of Water on Earth Five Officially Named Oceans Pacific, Atlantic, Indian, Arctic and Southern
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3 Latitude / Longitude Los Angeles is at 34º N, 118º W or… +34º Latitude, -118º Longitude Percent Area Covered by Physical Features Average Depth: 4 km 1. The average depth of the ocean is about 4 km 2. Three quarters of the atmosphere's mass is within 12 km of the planetary surface. The ocean thickness would be 1.5 mm The atmospheric thickness would be about 4.5 mm If you scaled the earth down to the size of a beach ball (1/2 meter diameter)… Comment About A Student Question During Last Lecture… Space Shuttle Photo of Earth
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4 Development of Plate Tectonics • Initially Proposed by Alfred Wegener as “Continental Drift” in 1915 – Not well acepted because while the evidence that drift had occurred was overwhelming, the proposed forcing mechanism (tidal action of moon) was certainly wrong. • Finally accepted when “Sea-Floor Spreading” was discovered in Post-WWII exploration. – This was the correct forcing mechanism that Alfred Wegener had missed Fit of Continents Many naturalists had noticed the apparent fit of the continents , including Englishman Francis Bacon and Italian geographer Antonio Snider-Pellegrini , whose 1858 map is shown above. Paleobiogeography
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This note was uploaded on 09/28/2008 for the course EAS 1540 taught by Professor Monger during the Fall '07 term at Cornell University (Engineering School).

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13_Review_Prelim1 - Review for Prelim 1 Origin and Earth...

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