Geog 1113 Notes- Week 2
Geog 1113 Notes- Week 2 GEOG 1113
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This 3 page Class Notes was uploaded by Victoria Koehl on Monday September 5, 2016. The Class Notes belongs to GEOG 1113 at Georgia State University taught by Larry Kleitches in Fall 2016. Since its upload, it has received 8 views.
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Date Created: 09/05/16
Geog 1113 Notes Fire Lake Earth is a dynamic planet whose surface is actively shaped An exogenic system includes external processes that set air, water, and ice into motion, and is powered by solar energy; it is a fluid realm that shapes and/or reduces landscape An endogenic system includes internal processes that produce flows of heat/material from deep below the crust, and is powered by radioactive decay; it is a solid realm To what extent is the Earth's crust actively building? The U.S. Geological Survey reports that in an 3 3 average year continental margins and seafloors expand by 1.9 km , but 1.1 km are consumed resulting in a net addition of .8 km The geological time scale breaks Earth into time periods: Eons (1 billion years), Eras (at least 50 million years), Period (longer than an epoch and within an era), Epoch (less than 10 million years ago) The sequence of the scale is based on the positions of rock strata above or below one another Superposition states that rock and sediment always are arranged with the youngest on top and the oldest on the bottom, if not disturbed The absolute ages on the scale are determined by scientific methods such as dating by radioactive isotopes Both relative and absolute dating methods calibrate the geological time scale Relative dating determines the sequence of events and time intervals between them, technological means, especially radiometric dating, determines absolute dates Anthropocene is a proposed epoch that began when human activities began to greatly impact the Earth's geology and ecosystem Will Steffen recommends starting the epoch when the Industrial Revolution began in the 1800's or with the Atomic Age in the 1950's Neither the International Commission on Stratigraphy nor the International Union of Geological Sciences have yet to officially approve the term Uniformitarianism Assumes that the same physical processes active in the environment today have been operating throughout geological time, "The present is the key to the past" Catastrophism Is a philosophy that attempts to fit the vastness of Earth's age and complexity of its rocks into a shortened time span; due to little physical evidence it is considered a belief rather than a scientific hypothesis Layers are defined by composition Three principal compositional layers: Crust The comparatively thin outer skin than ranges from 3 km at oceanic ridges to 70 km Mantle A solid, rocky shell that extends to a depth of about 2900 km Core An ironrich sphere having a radius of 3486 km Layers defined by physical properties Lithosphere "Sphere of rock", consists of the crust and upper mantle, relatively cool, rigid shell, about 100 km of thickness Asthenosphere "Weak sphere", beneath the lithosphere, from the upper mantle to a depth of about 600 km, small amount of melting in the upper portion that mechanically detaches the lithosphere from the layer below allowing the lithosphere to move independently of the asthenosphere Mesosphere Or the lower mantle, rigid layer b/w the depths of 660 km and 2900 km, rocks are very hot and capable of very gradual flow Outer core Mostly composed of ironnickel alloy, a liquid layer, 2270 km thick, generates Earth's magnetic field by convection flow Inner core Sphere radius of 3486 km, stronger than the out core, presumed to behave like a solid Discontinuity is a place where change in physical properties occur b/w two regions in Earth's interior – the crust and rest of the lithosphere is called the Mohorovicic discontinuity, b/w the mantle and liquid outer core is the Gutenburg discontinuity The entire crust is in a constant state of compensating adjustment, or isostasy, slowly rising and sinking due to its own weight, and pushed/pulled by currents in the asthenosphere Ex: Mountain mass slowly sinks (erosion), because of this loss the crust adjusts upward, deposition of the sediments from the mountain deforms the lithosphere downward Hydrologic cycle A vast system that circulates water, water vapor, ice, and energy throughout the Earthoceanenvironment, rearranges Earth's materials through erosion, transportation, and deposition Rock cycle Through processes in the atmosphere, crust and mantle, produces three basic rock types: igneous, sedimentary, and metamorphic rock Igneous rock is a rock that solidifies and crystalizes from molten lava Sedimentary rock is formed through pressure Metamorphic rock is any rock (igneous or sedimentary) can be transformed into this rock type by going through profound physical or chemical changes and increased temperature Tectonic cycle Brings heat energy and new materials to the surface and recycles old material to the mantle, creating movement and deformation of the crust Mineral Inorganic natural compound having specific chemical formula and possessing a crystalline structure, each mineral has its characteristic hardness, color, and density, there are about 3000 minerals but 20 are common rockforming minerals Rock An assemblage of minerals bound together, or a mass of a single mineral Magma is fluid, highly gaseous, and under tremendous pressure; is either intruded into country rock (preexisting rock), or extruded onto the surface as lava 2 The cooling history of rock how fast it cooled, and how steadily the temperature dropped determines its texture and degree of crystallization Sedimentary rocks form from existing rocks that have been weathered, transported, and deposited; sedimentation is driven by solar energy and gravity, with water as the principal medium Lithification The process of cementation, compaction, and hardening of sediments Alfred Wagner Considered the architect of the continental drift, came up with the idea that Earth's landmasses migrate "Continental Puzzle", based it on physical evidence: matching fossils on different landmasses, similar rock types found on different landmasses, and mountain belts end on one continent appear on another; his book Origin of the Continents and the Oceans Further evidence to the continental drift provided by spreading ridges and subduction zones which are areas of earthquakes and volcanic activities Midocean ridges were the direct result of upwelling flows of magma from the upper mantle; when mantle convection brings magma to the crust the crust is fractured creating new seafloor When continental crust and oceanic crust collide, the heavier ocean floor will go beneath the continent creating a subduction zone; these zone coincide with oceanic trenches and are the deepest features of the Earth's surface This process resulted in the breakdown of the supercontinent Pangea Three types of plate boundaries: Divergent boundaries are characteristic of seafloor spreading centers, where new seafloor is formed and crustal plates spread apart Convergent boundaries are characteristics of collision zones, where continental/oceanic crusts collide, zones of compression Transform boundaries occur where plates slide past each other at right angles to a seafloor spreading center, neither divergent nor convergent, no volcano eruptions 3
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