Physical Geography Week 10 Notes
Physical Geography Week 10 Notes GEOG 101 001
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GEOG 101 001
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This 4 page Class Notes was uploaded by Julia Parenti on Monday April 18, 2016. The Class Notes belongs to GEOG 101 001 at Towson University taught by Dr. Ken Barnes in Spring 2016. Since its upload, it has received 10 views. For similar materials see Physical Geography in Geography at Towson University.
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Date Created: 04/18/16
Physical Geography Earthquake Hazards Geologic evidence demonstrates that major earthquakes have occurred throughout geologic history so do recent current events Normal processes Most earth movements are minor and can only be detected with the use of sensitive seismometers it is estimated that globally 1 million tremors occur each year, however, only 10 percent are felt by people The big ones can be catastrophic, with staggering losses of lives Shensi province earthquake in sixteenth century China led to more than 800,000 dead the Lisbon Portugal earthquake of 1755 killed nearly 60,000 Tangshan earthquake of 1976 over 300,000 deaths the casualties such as these and massive destruction of property make the study of earthquakes and their prediction a high priority Earthquake Zones Pacific Rim Accounts for 70% of world’s earthquakes Also known for its concentrations of volcanoes Mid Ocean Ridge MidAtlantic Ridge Mediterranean Basin Indian Ocean East African Rift Zone Intraplate earthquakes occur but are less common Causes of Tsunamis Earthquakes (main cause) Sudden crustal subsidence beneath the ocean Massive slope failures of large volcanic islands (super slides) Massive marine sediment slides Submarine volcanic eruptions Large rockfalls into confined bays Volcanism Fluid state movement of the Earth’s crust produces intrusive and extrusive features Volcano: vent by which gases, liquids, solids from the interior are ejected or extruded onto the surface Extrusive Landforms and features pyroclastic materials: solid materials ejected from vents Lava plains and plateaus: produced by fissure eruptions Volcanic cones shield: large broad cone with shallow slopes (lava) composite (stratovolcano) steep layered cones (ash and lava) cinder: small, steep sided, wide crater (pyroclastic materials) Geothermal features geyser: fountain of superheated water that spray periodically hot spring: water heated by contact with hot rocks mudspot: gaseous mud and water fumerole: steam vent Geographical Distribution of Volcanoes There are about 500 active volcanoes globally many more are extinct or dormant we do not know precisely how many volcanoes are on Earth, but it is in the tens of thousands there are at leasy 10,000 in the pacific approximately half of the world’s total Are Volcanoes Major Killers? Yes and No Estimated that over the past 500 years volcanoes have caused only 200,000 fatalities Average 400 victims per year 100 people per day die on highways Volcanic eruptions do cause extensive property damage and destruction over wide areas but human casualties are usually low why? lots of advanced warning of eruptions Volcanic Hazards Lava flows Lahars: volcanic mudflows Lecture 18 Rocks, Weathering and Erosion Rocks and Minerals Rocks: Naturally formed aggregates or masses of mineral matter. Minerals retain their individual identity within rock masses bedrock: solid rock layer regolith: weathered rock material above bedrock outcrop: exposed bedrock Minerals: Naturally occurring inorganic crystalline compounds with welldefined combinations of atomic elements and unique chemical formulas stuff that rocks are made from Rock Types Igneous: Formed by the solidification of hot mile materials 80% of the earth’s crust is igneous rock, but do not comprise the greatest proportion on the surface Intrusive: (ex: granite) and Extrusive (ex: basalt) Forms Sedimentary: hardening of layered accumulations (strata) of mineral materials or chemical precipitates derived from previously existing rock or from organic matter examples: sandstone, limestone, bituminous coal most common rock on the surface*** bedding planes: indicated changes in the environmental conditions under which the sediments were deposited deep to shallow water marine shallow marine to landstream deposition stream to wind deposition, etc. Metamorphic: Igneous or sedimentary rocks that have been changed physically or chemically through heat or pressure or both examples: anthracite coal (hard coal), slate, marble, schists, gneiss and quartzite Weathering: Physical and chemical breakdown of rock material Rates of weathering are temperature and water dependent Weathering is important for many reasons soil formation via the creation of regolith biogeochemical cycles via the release of soluble nutrients from the soil and parent materials creation of new compounds accumulation of certain metallic ores such as bauxite and iron ores Types of Weathering Physical Chemical Types of Physical Weathering Joint and Fracture Formation: producted by earthquakes or related activites or by unloading Frost Wedging: Water freezes and expants in cracks splinters rock important in the middle and high latitudes and in high mountains produces talus Salt Crystal Growth: crystals wedge rocks apart Thermal expansion and contraction: associated with the heat from wildfires Hydration: temporary adhesion of water molecules to rock minerals causes minerals to shrink and swell Biological Action: tree roots, animals borrowing, etc. Chemical Weathering Processes Hydrolysis: permanent chemical combination of water molecules with minerals. Weakens minerals Oxidation: chemical combination of minerals with oxygen Carbonation: chemical reactions of rock materials with carbonic acid converts oxides to more soluble forms Solution: dissolving of rock materials in water Weathering and Climate Different types of climates have different types and rates of weathering Physical and chemical weathering processes occur simultaneously; however, their rates vary by climate in cold climates and dry climates physical weathering dominates in hot, wet climates, chemical weathering dominates Differential Weathering and Landscapes Differential weathering of rock can produce some pronounced and oftern dramatic landscape contrasts. in dry areas, limestone is a ridge former in humid areas, limestone is a valley former Sequence of Gradation Weathering Erosion Transportation Deposition
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