Geog week 2
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This 4 page Class Notes was uploaded by Kadijah Hamki on Tuesday August 30, 2016. The Class Notes belongs to GEOG 1113 at Georgia State University taught by Kleitches in Fall 2016. Since its upload, it has received 5 views. For similar materials see INTRO TO WEATHER & CLIMATE in Geography at Georgia State University.
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Date Created: 08/30/16
Earth is a dynamic planet whose surface is actively shaped by physical agents of change: - External (exogenic); ex: precipitation. Includes external processes that set, air, water (streams and waves), and ice into motion, powered by solar energy. This is the fluid realm of earth’s environment. o These sculpting agents that carve, shape, and reduce the landscape. - Internal (endogenic): encompasses internal processes that produce flows of heart and material from deep below the crust, powered by radioactive decay o This is the solid realm of earth. To what extent is Earth’s crust actively building at this time in its history? - According to U.S. Geological Survey- expand by 1.9 km^3 but at the same time 1.1 km^2 is consumed, resulting in a net addition of 0.8 km^3 to earth’s crust. - Results in irregular patterns off surface fractures, earthquakes, volcanic activity and formation of mountain ranges. How is geological time scale organized? - Eons: 1 billion years - Eras: usually at least 50 million years - Periods: longer than epochs but shorter than eras - Epochs: usually less than tens of millions of years ago. What is the basis? - Based upon the relative positions of rock strata above or below one another. - Important general principle >> superposition rock and sediment always are arranged with youngest beds near the top of a rock formation and the oldest at the base. IF THEY HAVE NOT BEEN DISTURBED. - Carbon dating - We are in ph--- eon, Cenozoic era, - 90% of geologic time was in Precambrian eon The Anthropocene - Proposed epoch that began when human activities started to have a significant global impact on earth’s geology and ecosystems. - Will Steffen has recommended starting the epoch with the advent of the industrial revolution in early 1800s or with the atomic age in 1950s. Uniformitarianism and catastrophism - Uniformitarianism assumes that same physical processes active in the environment today have been operating throughout geologic time. “The present is the key to the past”. - Catastrophism attempts to fit the vastness of earth’s age and the completely of its rocks into a shortened time span. More appropriately considered a philosophy rather than a serious scientific hypothesis. What is the structure of earth’s interior? - 3 compositional layers o Crust: comparatively thin outer skin that ranges from 3km (2 miles) at the oceanic ridges to 70km (40 miles in some mountain belts). o Mantle: solid rocky (silica-rich) shell that extends to a depth of about 2900 km (1800 miles). o Core: an iron-rich sphere having a radios of 3486 km (2161 miles). - Layers defined by physical properties o Lithosphere: (sphere of rock): consists of crust and uppermost mantle, relatively cool, rigid shell. Averages about 100 km in thickness, but may be 250 km or more thick beneath the older portions of the continents. o Asthenosphere: (weak sphere): beneath the lithosphere, in the upper mantle to a depth of about 600 km. Small amount of melting in the upper portion mechanically detaches the lithosphere from the layer below allowing the lithosphere to move independently of the asthenosphere. o Mesosphere: lower mantle, rigid layer between the depths of 660 km and dd 2900 km. rocks are very hot and capable of very gradual flow. o Outer core: composed mostly of an iron-nickel alloy. Liquid layer, 2270 km thick. Convective flow within generates earth magnetic field. o Inner core: sphere with a radios of 3486 km, stronger than outer core. Behaves like a solid. What Is discontinuity? - Place where a change in physical properties occurs between two regions deep in earth interior. - Mohorovicic discontinuity- boundary between the crust and the rest of the lithospheric upper mantle. - Guttenberg discontinuity- Earth’s entire crust is in a constant state of compensating adjustment (isostasy) - Example: Mountain mass slowly sinks. Hydrologic cycle - System that circulates water, water vapor, ice, and energy throughout the earth-atmosphere- ocean environment. - Rearranges earth material through erosion, transportation, and deposition, and it circulates water as the critical medium that sustains life. Rock cycle and tectonic cycle - Rock cycle: produces three basic rock types: o Igneous: solidifies and crystalizes from molten state (lava). o Sedimentary: formed through pressure, the cementation, compaction and hardening of sediment. o Metamorphic: any rock can be transformed into metamorphic rock 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 mantle depths, creating movement and deformation of the crust. What is a mineral? Rock? - Mineral: inorganic natural compound having specific chemical formula and possessing a crystalline structure. Appox: 3000 minerals but only 20 are common rock-forming - Rock: assemblage of minerals mound together or sometimes a mass of a single mineral. Intrusive and extrusive types of igneous rocks - Igneous rocks are aggregates of minerals that crystalize from molten material generate within earth’s interior - The heat to generate the molten material comes from within the earth - Types depends on factors: o Original chemical composition of the magma o _ o _ - Magma is fluid, highly gaseous, and under pressure. - It is either: intruded into country rock or extruded onto the surface as lava. Sedimentary profess and lithification - Sedimentary rocks form from existing rocks that have been weathered, transported, and deposited - Lithification: the process of cementation, compaction, and hardening of sediments. - Sedimentation is driven by solar energy. Medium is water. Metamorphic rock - _ Alfred Wegener - Continental puzzle Three types of plate boundaries - Divergent: seafloor spreading centers, where upwelling material from the mantle forms new seafloor, and crustal plates are spread apart; boundary where the two plates are moving away from each other. - Convergent: a boundary where two separate plates are pushing into each other - Transform: two plates slide by one another in opposite directions.
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