SUS 202 Week 10 Lithosphere
SUS 202 Week 10 Lithosphere SUS 202
Popular in Dynamic Earth Systems
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This 5 page Class Notes was uploaded by Noah Thompson on Sunday March 20, 2016. The Class Notes belongs to SUS 202 at Chatham University taught by Dr. Ryan Utz in Winter 2016. Since its upload, it has received 30 views. For similar materials see Dynamic Earth Systems in Sustainability at Chatham University.
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Date Created: 03/20/16
The Lithosphere Part 1 Where did energy in a hot spring originate? o Magma from under ground o Fault Line o Formation of Earth (energy stored in the core; insulating the energy) Two processes for the rock cycles: The endogenic system—processes operating in Earth’s interior, driven by heat and radioactive decay Exogenic system—processes operating at Earth’s surface, driven by solar energy and the movement of air, water, and ice (weathering) Pace of Change An assumption is that the movements, systems, and cycles that occur today also operated in the past. Uniformitarianism, assumes that the same physical processes now active were operating through Earth’s history. The scope of Earth’s history can be shown in a timeline known as the geologic time scale. This breaks the past 4.6 billion years down into eons, and then into the shorter time spans of eras, periods, and epochs. Relative age refers to the age of one feature with respect to another within a sequence of events. *Density of rock follows the same rules as air/water, dense rock is lower in layers compared to less dense rocks* As Earth solidified, gravity sorted materials by density. Earth’s interior consists of roughly concentric layers, each distinct in either composition or temperature A third of Earth’s entire mass, but only a sixth of its volume, lies in its dense core. The core is differentiated into two regions— inner core and outer core—divided by a transition zone several hundred kilometers wide. Lower and upper mantles are about 80% of Earth’s total volume. Earth’s Crust • Eight natural elements make up over 98% of Earth’s crust by weight, and just oxygen and silicon account for 74.3%. • Continental crust differs greatly from oceanic crust in composition and texture. The difference has a bearing on the dynamics of plate tectonics and continental drift. • Continental crust is relatively low in density, averaging 2.7 g/cm , and is composed mainly of granite. • Oceanic crust is denser than continental crust, averaging 3.0 g/cm and is composed of basalt. Buoyancy is the principle that something less dense, such as wood, floats in something denser, such as water. The balance between the buoyancy and gravitational forces is the principle of isostasy. The Rock Cycle • Although rocks appear stable and unchanging, they are not. • The rock cycle refers to the continuous change of Earth materials from one rock type to another. • Igneous rock formed from magma may break down into sediment by weathering and erosion, where it may then lithify into sedimentary rock. • This rock may become buried and exposed to pressure and heat deep within Earth, forming metamorphic rock. • Tectonic refers to changes in the configuration of Earth’s crust as a result of internal forces. • Plate tectonics is the theory that the lithosphere is divided into a number of plates that float independently over the mantle. • Along plate boundaries occur the formation of new crust, the building of mountains, and the seismic activity that causes earthquakes. Seafloor Spreading The key to establishing the theory of continental drift was a better understanding of the seafloor crust. • As scientists got data about the depth variations of the ocean floor, they saw an interconnected worldwide mountain chain. • When one portion of the lithosphere drops under another and dives down into the mantle, the process is called subduction, and the area is a subduction zone. • When continental and oceanic crust slowly collide, the denser ocean floor will grind beneath the lighter continental crust, thus forming a subduction zone. • The world’s deepocean trenches occur with these subduction zones and are the lowest features on Earth’s surface.