Introduction to Physical Geography - Exam 3 Study Guide | GEOG 1111, Study notes of Geography

Download Introduction to Physical Geography - Exam 3 Study Guide | GEOG 1111 and more Study notes Geography in PDF only on Docsity! Geography Exam #3 Geomorphology: The science of landforms; their origin, evolution, form, and spatial distribution. *development and changes on the Earth’s surface over time 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 operating at the present time Landform: individual element of a landscape; ex: mountain, river, hill, etc. 1. Tectonic: developed by the rearrangement of the Earth’s crust (internal) 2. Fluvial: developed by moving liquid water 3. Glacial: developed by glacial ice (solid water) 4. Coastal: developed by waves 5. Eolian: developed by wind Equilibrium states -Steady-state: little change, with inputs and outputs equal -Dynamic: fluctuates around an avg. value, demonstrates a trend over time Earth’s Internal Structure -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 (BYBP) *We know this because of indirect evidence of seismic waves *cooler=higher velocity; hotter= slower velocity 3 types of seismic waves: P waves: push or compressional waves (go through the mantle, outer and inner core, but change direction etc.) S waves: shear or shake waves (go only through the mantle) L waves: surface waves, the ones we feel INNER CORE -lowest part of core -solid and rigid -consists of iron (Fe) and nickel (Ni) OUTER CORE -liquid molten, more plastic -consists of Fe and Ni, but at a lower pressure so its’ melting T is lower=liquid -generates 90% of the Earth’s magnetic field *Gutenberg Discontinuity: an uneven, broad transition zone between the outer core and the lower mantle *discontinuity: a physical difference, esp. density, between two layers LOWER MANTLE -solid -consists of oxides of Fe, magnesium (Mg) and silicon (Si) UPPER MANTLE -partially molten -consists of silicate materials *upper and lower mantle comprise about 80% of Earth’s volume ASTHENOSPHERE -molten -source of magma which pushes up into the crust & onto the surface LITHOSPHERE -uppermost, solid portion of mantle, plus the crust -zone of contact between the uppermost mantle and the crust is the Mohorovicic discontinuity -Moho is closer to the surface under oceanic crust vs. continental crust Continental crust vs. Oceanic crust -usually lower density -higher density -sialic rock or sial (Si & Al) -simatic rocks or sima (Si & Mg) -ex: granite, shale, marble -ex: basalt, lava Topographic relief: the vertical difference between highest elevation and lowest -high relief (mountains) vs. low relief (coastal plain) -oldest rocks on the planet are about 4 billion years old Plate Tectonics -the theory of global dynamics in which the lithosphere is believed to broken into individual pieces or plates that move in response to convection in the upper mantle Wegener: German meteorologist, Theory of Continental Drift, landmass=Pangea Sea-Floor Spreading: the movement of crustal material by the upwelling of magma along a system of mid oceanic ridges -the upwelling pushes the crust away from the ridge -oldest crust is furthest from the ridge, newer crust closest -oldest sea floor dated so far formed ~200 MYBP -idea of magnetic reversals or paleomagnetism enhanced this theory Magnetic reversals/paleomagnetism: refers to the magnetic alignment of charged particles (esp. Iron material) in the rock which exhibit a symmetrical pattern as you move away from the mid-oceanic ridge Divergent plate boundaries: -where plates are moving apart from each other -under tensional stress -created by upwelling of magma (ridge push) and slab pull -areas of abundant earthquake activity and relatively mild volcanic activity -sea floor spreading along mid oceanic ridges Ex: along the mid-Atlantic Ridge or the creation of the Red Sea -on continents may form rift zones or valleys Ex: Great Rift Valley of East Africa Convergent plate boundaries: -under compressional stresses -create subduction zones & areas of high earthquake activity 3 types: Oceanic-continental -oceanic crust (which is denser) is subducted (forced) under the continental crust (which is less dense) & re-melted in the Asthenosphere -this creates an underwater trench along the plate boundary -continental crust is compresses , forming folded mountains and volcanic mountains where magma reaches the surface through cracks and weak points -high earthquake and volcanic activity Ex: Nazca & South American plates converge creating the Peru Trench underwater, the Andes mountains, also in the Pacific NW of the US Oceanic-oceanic -subduction of one plate and remelting of it -deep trenches created at the boundaries -high level of volcanic and earthquake activity -formation of volcanic island archipelagoes Ex: the Philippine islands, Japanese islands, and the Aleutians off Alaska Continental-continental -areas of great compression and mountain building -high earthquake activity, but little or no volcanism -little or no subduction of continental crustal material Ex: the Appalachians, the Himalayas Transform/ Lateral plate boundaries: -areas of shear stresses -transform faults created -high earthquake activity & some crustal deformation -no subduction or volcanism Ex: San Andreas Fault Zone Volcanism Extrusive Volcanism Volcano: a landform with a vent, or fissure (crack) on the surface, which is the end of a conduit originating from below the crust in the Asthenosphere -often a mountain landform, (fissures usually do not form features of high relief) -magma originating in the Asthenosphere is expelled through the conduit and out the vent -magma often collects in a magma chamber below the volcano before expelled Crater: the surface depression at the summit of the volcano -a volcano may be categorized as Active: currently erupting, or has erupted during recorded history Dormant: an active volcano that is in repose but is expected to erupt in the future Extinct: a volcano that is not expected to erupt again -75% of volcanoes are on the sea floor -most convergent and divergent plate boundaries have high volcanic activity -hot spots are also areas of high volcanic and earthquake activity Lava: the molten rock issued from a volcano; the term used for magma once it has erupted onto the Earth’s surface 2 types of lava: mafic: (basaltic lava) high in Mg & Fe, <50% silica thus less viscous which means it flows readily, and thus less gas is trapped within leading to a less explosive eruption felsic: richer in silica thus more viscous meaning it flows slower; it is also more acidic and more gases are trapped leading to more explosive eruptions 2 types of eruptions: effusive: relatively gentle, non-violent eruptions because gases readily escape, thus less explosive, material issued is primarily mafic magma, if eruption is through a vent it may form a shield volcano (Islands of Hawaii, Galapagos), if eruption is through a fissure it forms a plateau basalt or flood basalt (Columbia Plateau) explosive: relatively violent eruptions because conduit often gets plugged with cooled/solidified magma, and thus a greater amount of gases are trapped in the magma increasing pressure, material issued is primarily felsic magma with a much greater content of pyroclastics, if the eruption is through a vent and this often forms a composite volcano or stratovolcano (Mt. St. Helens, Mt. Ranier, Mt. Vesuvius) **lahar or pyroclatic flow may accompany an explosive eruption lahar: a flood of ash, mud, and water created by melting of snowcap during an eruption or volcanic event nuée ardentes/ pyroclatic flow: a cloud of hot volcanic gas and ash that moves down the flanks of the volcano *Phreatic eruptions: violent eruptions made more severe by water entering the magma chamber, increasing pressure from steam & increasing the explosive power Ex: Kratatau, Santorini Caldera: a large, more or less circular depression or basin associated with a volcanic vent, its diameter often many times greater than the original vents, may be the result of collapse or subsidence or may also result from an explosive event Hot spot: the surface expression of a mantle plume that has either created or found a crack in the crust, creating a conduit to the surface Intrusive Volcanism: (plutonic landscapes) -landforms and features whose origin is from the cooling of magma below the surface (within the crust) pluton: a body of intrusive igneous rock 2 main types of intrusive volcanism: Discordant: disrupts or changes (often melts or metamorphoses) the existing geologic structure it intrudes; creates a space and then fills it in