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Unit 3 - INTRODUCTION TO GEOMORPHOLOGY Definition The...

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INTRODUCTION TO GEOMORPHOLOGY Definition: The science of landforms; their origin, evolution, form, and spatial distribution * The development and changes on the earth’s surface over time. Basic Terms: Landform: individual element of a landscape EX: a mountain, a river, a hill, etc. Topography: Earth's ridges, valley's & other surface features; the change in elevation over the Earth’s surface Uniformitarianism: The theory that geologic events are caused by natural processes, many of which are still operating at the present time. * and that the processes we see today operate in the same way today as they did in the past EX: the way a volcano operates today is the same as it did 1000 yrs ago, or 1million years ago, or 1 billion years ago ** Types of Landforms: Tectonic: developed by the rearrangement of the Earth’s crust, driven by internal energy Fluvial: those developed by moving liquid water Glacial: those developed by glacial ice(solid water) Coastal: those developed by waves Eolian: those developed by wind ** Landforms and systems change, but tend to be in some form of an equilibrium state, when viewed over geologic time. Steady-state: Little change, with inputs and outputs equal
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Dynamic Equilibrium: fluctuates around an average value, but demonstrates a trend over time Geomorphic Processes: relationship between external and internal processes and forces * Internal Processes: those processes which occur or originate within Earth’s crust; volcanism, diastrophism (mountain building), plate tectonics (massive crustal rearrangements) * External Processes: those processes which occur on the Earth’s surface; weathering & erosion by fluvial, glacial, eolian, & coastal EARTH'S INTERNAL STRUCTURE Characteristics: * arranged in concentric layers * heavier elements towards the center * each layer distinct in chemical composition or temperature * result of cooling since formation of the earth, some 4.6 billion years before present(BYBP) ** How do we know? * Only by indirect evidence; seismic waves * analyzing the behavior of seismic waves; their speed and direction ** cooler = higher velocity; hotter = lower velocity ** density may reflect or refract the waves ** 3 types of seismic waves: P waves: push or compression waves – go through anything S waves: shear or shake waves – not through liquids
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L waves: surface waves, the ones we feel - The Earth's Layers: Inner Core: * solid and rigid * consists of iron and nickel * 3200 mi below sea level (bsl), 760 mi thick Outer Core: * liquid molten state , more plastic * consists of iron and nickel, but at lower pressure so its melting T is lower = liquid * 1800 mi bsl; 1400 mi thick * generates 90% of the Earth's magnetic field – changes field around ** Gutenberg discontinuity: an uneven, broad transition zone between the Outer Core and the Lower Mantle – know they are there because of seismic activity * discontinuity: a physical difference or change, esp. density, between two layers Lower Mantle: * solid. Word.
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