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Earth's Structure, Materials, and Plate Tectonics: Crust, Mantle, and Geological Processes, Study notes of Geography

An overview of the earth's structure, focusing on the different layers, including the core, mantle, and crust. It discusses the composition, properties, and behaviors of each layer, as well as the formation of rocks and the geological processes of plate tectonics, including the mohorovicic discontinuity, seafloor spreading, and tectonic plate movements.

Typology: Study notes

2010/2011

Uploaded on 05/08/2011

alaskablue2
alaskablue2 🇺🇸

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Download Earth's Structure, Materials, and Plate Tectonics: Crust, Mantle, and Geological Processes and more Study notes Geography in PDF only on Docsity!

Chapter 13: Earth Structure, Earth Materials, & Plate Tectonics

 Structure of earth (less dense near surface; more dense towards core)

Core Mantle Crust

o 1/3 of mass o Iron & nickel o Inner & Outer Core: link btw pressure, temp, mineral melting pt

  • Inner = solid
  • Outer = molten o 2/3 of mass; largest o Solid, rocky material o Behaves as plastic solid(deform & flow)

o 1% of mass; less dense

o Diff btw oceanic & continental crust (density)

  • location, composition, thickness Layers: Oceanic Crust o Composition: -Basaltic (dark, fine-grained; extrusive) o Thickness:
  • thinner (denser) Continental Crust o Composition:
  • Granitic (light, coarse grained; intrusive) o Thickness:
  • thicker (less dense) Lithosphere (crust & top part) o Elastic Solid: rigid & brittle, stand stress to brink then fracture Asthenosphere (lower part) o Plastic solid o Vertical & horizontal movement o Thermal currents o Heat Source: radioactive decay o Energy source  Mohorovicic Discontinuity – boundary btw mantle & crust; change in density; varies in depth; fast change in speed of seismic waves b/c fast change in density  Rocks – aggregation (collection) of minerals

Igneous Rocks Sedimentary Rocks Metamorphic Rocks

o Cooled & solidified molten rock material o Magma: subsurface o Lava: surface; only one we can see o Extrusive: surface (outside), lava, cools fast-smooth o Intrusive: beneath surface (inside), magma, cools slow-grainy o Formed from added sediments o Eroded, transported, deposited o Horizontal layers o Pressure from above-shrinks pore space & squeezes out water o Clastic: formed by fragments of pre-existing rocks o Organic: solid rock from remains of organisms(plants & animals) o Chemical: dissolved added & deposited on sea/lake bottom o Charged form

  • by intense heat & pressure within crust
  • stays in solid form(bonds btw atoms broken & rearrange into more stable form
  • altered=harder & more compact
  • weather resistant ROCK CYCLE (don’t go in perfect circle) o Form: cooled magma/lava o Can melt/reform into new o Can alter into met rocks o Can weather into fragments-eroded, transported, deposited to form sed rocks o Consist of particles from any o Can alter into met rocks o Sed or ig can be altered into met rocks o Can melt into magma & form ig rocks  Early theories o Catastrophism – spontaneous formation o Uniformitarianism – inner & outer processes, still used today; operate at varying rates & magnitudes  Continental Drift theory o Alfred Wegener (climatologist) early 1900s; landmasses/continents shifted position o Evidence: fit of coastlines, similarities in animal & plant fossils(once together), past glaciations o Weakness: no cause-needed energy source o Supporting: 1950s/60s; changing course of magnetic fields in basaltic rocks  Paleomagnetism – iron rocks & minerals indicate magnetic field when they solidified; revealed- continents were grouped together 200 million yrs ago & polarity reversed  Plate Tectonics – modern theory, movement of continents; litho broken into several plates=sit on plastic flowing aestheno o Evidence of plate tectonics found when studying sea floor:  1) similarity btw midoceanic ridges & continental coastlines  2) magnetic bands moving away from mido

 3) young rocks on sea floor  4) oldest rocks near continents & get younger towards mido  5) hottest rocks found near mid & become cooler away from mido  Seafloor Spreading – new crust created near mid & older crust being destroyed along other margins; powered by subcrustal convection cells o Warm mantle rises near mid, spreads out laterally, fractures seafloor where molten basalt wells up & cools = forming new ocean floor  Tectonic Plate Movement – understanding ways plates move allow us to better understand = earthquakes, volcanoes, zones of crustal movement, major landform features Divergence Convergence Transform o 2 plates pull apart

  • seafloor spreading/mido(ocean )
  • Rift Valleys (land) o 2 plates push together o Subduction: denser plate forced under less dense plate - descend into aestheno-melted into molten=recycled - create friction=explains major earthquakes - explains spatial dist of mt ranges, volcanoes, ocean trenches o Lateral plates slide past one another in opposite directions o Transform Fault: divergent boundary occurs in crosshatched pattern-create transform movement - common along mido  Hot Spots – stationary molten masses o Oceanic plate moves over hot spot - upper mantle & oceanic crust melt - causes volcanic eruptions & outpouring of basaltic material - creates volcanic island  Accretion – most supported process for continental growth; adding large pieces of crust along border by plate tectonic collision Questions and things must know for Final:
  1. Oceanic & continental crust – which one is more dense? – oceanic crust
  2. Where is Moho located and what is it?
  3. 7 major plates slide: where are we most likely to see a trench/volcano/mt forming/rip valleys/etc.? a. Dotted lines are….. Lines are….. b. Letters on plates identify what?
  4. Must know all boundaries
  5. Less dense near surface/more dense towards core
  6. Focus on how rocks are formed