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Geology Exam1 Study Guide

Geology Exam1 Study Guide - Geology Study Guide Exam 1...

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Geology Study Guide – Exam 1 Chapter 2 – Journey To The Center of the Earth Layers o The Earth consists of three layers: Crust Mantle Core o Oceanic crust is mafic in composition, whereas average continental crust is felsic to intermediate. At the top of oceanic crust, we find a layer of sediment (clay and tiny shells), then a layer of basalt and below that a layer of gabbro. Continental crust contains a great variety of rock types, ranging from mafic to felsic (granite, basalt, gabbro). Oxygen is the most abundant element in the crust. o The mantle is composed of ultramafic rocks called peridotite. Two sublayers: the upper and lower mantle with a transition zone o The core is made of iron alloy and consists of two parts: The outer core is liquid and the inner core is solid. Composition o The Earth consists of organic chemicals, minerals, glasses, rocks, metals, melts, and volatiles. Most rocks on Earth contain silica. We distinguish between felsic, intermediate, mafic, and ultramafic based on the proportion of silica (with felsic having the highest amount of silica). Physical Properties o The surface of the Earth is 30% land and 70% ocean. Earth’s land surface has a great variety of landscapes because of variations in elevation and climate. Earth is composed of liquids, solids, and gases. How We Know What’s Inside The Earth o Measuring Earth’s Density: Maskelyna postulated that he could weigh Earth by examining the deflection of a plumb bob attached to a surveying instrument. The angle of deflection was caused by the gravitational attraction of a
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mountain. His results led to an estimate that the Earth’s density is 4.5 times the density of water. The average density of Earth exceeds that of its surface rocks. o Measuring Earth’s Shape: Geologist compared the Earth to a hard-boiled egg with three layers: a not-so-dense crust like the shell, a denser, solid mantle in between like the egg white, and a very dense core like the yolk. o Clues From the Studies of Earthquakes: By detecting the depths at which earthquake’s waves velocities change, geoscientists pinpointed the boundaries between layers and even recognized subtler boundaries between layers. Difference Between Crust and Lithosphere o The crust plus the upper part of the mantle constitute the lithosphere. The lithosphere lies on top of asthenosphere, the portion of the mantle in which rock can flow. Chapter 3 – Drifting Continents and Spreading Seas Continental Drift o Continental drift hypothesis: Alfred Wegener proposed that continents had once been joined together to form a single huge supercontinent (Pangaea) and had subsequently drifted apart. Evidence for Continental Drift o Coastlines on opposite sides of the ocean match up o The distribution of late Paleozoic glaciers can be explained if the glaciers made up a polar ice cap over the southern end of Pangaea o The distribution of late Paleozoic equatorial climatic belts is compatible with the concept of Pangaea (coal and deserts).
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