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Geo. Chp.4,8,10 Notes for Website.docx - Chapter 4.1 Earths...

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Chapter 4.1: Earth’s Interior *Young Earth was very HOT, thus, its materials were molten or melted. -Why was it so hot? a. compression caused by spinning b. collisions w/meteorites c. decay of radioactive material - As the Earth cooled, its materials separated into layers by density ! (Much like salad dressing will form layers if you leave it sit!) Layers of Earth from the inside moving out: (p. 72) 1. inner core : Earth’s center; most dense materials here (Fe and N); solid 2. outer core : surrounds the inner core; also composed of Fe and N but in a liquid state 3. mantle : surrounds the core; thickest layer; composed of compounds rich in Fe, Si, and Mg; both a solid and a liquid 4. crust : outermost layer w/which humans have direct contact; thin, rigid layer of lighter rocks; 65 km deep; only layer where life has been found * lithosphere : uppermost portion of the mantle and the crust together * asthenosphere : thin, slushlike layer of the upper mantle, just below the lithosphere; responsible for movement of the Earth’s crust! *Earth’s magnetic field is due to the movement of the liquid Fe in the outer core ! This helps to prove that the Earth’s layers exist! - This movement creates an electric current, which produces a magnetic effect! - This is why a compass works! However, magnetic north is 11° different than true north. 8.1- What is Plate Tectonics? (p. 172-175) *Key Idea: The lithosphere is broken into rigid plates that move in relationship to one another on the asthenosphere. Plate Tectonics : a theory that describes the formation, movements, and interactions of these plates. Continental Drift : an early hypothesis about plate movement that says the continents drifted from one location to another over time. -Proposed in 1912 by Alfred Wegener -Based on 4 main pieces of evidence: 1. Shapes of the continents - especially S.America and Africa 2. Fossil evidence - certain fossil remains are only found in parts of S.America and Africa! (see p.172) 3. Climate evidence - coal deposits found in Antarctica and glacial groves found in Africa! 4. Distinctive rock formations - mountain ranges and rock types match up on different continents!
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-Biggest weakness in Wegener’s hypothesis : He couldn’t explain HOW the continents moved! In the 1950’s and 1960’s, scientists made new discoveries that led to the theory of plate tectonics. -We now know that the continents are embedded in lithospheric plates, and as these plates move, they carry the continents with them. -More evidence of plate tectonics: 1. Locations of volcanoes and earthquakes - They do not occur randomly, but occur mostly in concentrated belts along the plate boundaries! (see p.173 and p.712) - Volcanic activity is due to the high heat flow along boundaries, where magma moves up to the Earth’s surface. - Earthquakes occur when strain builds up and is released in the rocks along these boundaries.
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