earth systems science chapter 7 i.structure of the earth ii.plate tectonics the solid part of the...
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![Page 1: Earth Systems Science Chapter 7 I.Structure of the Earth II.Plate Tectonics The solid part of the earth system includes processes, just like the atmosphere](https://reader036.vdocuments.mx/reader036/viewer/2022062407/56649d365503460f94a0d888/html5/thumbnails/1.jpg)
Earth Systems ScienceChapter 7
I. Structure of the Earth
II. Plate Tectonics
The solid part of the earth system includes processes, just like the atmosphere and oceans. However, the time scales for processes in the solid earth are much longer. As a result, solid earth processes are important for climate over much longer time scales (e.g. millions of years).
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Earth Systems ScienceChapter 7
I. Structure of the Earth
1. Seizmology, structure of the earth
2. The crust and lithosphere
3. The mantle
4. The core
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Seismology: study of earthquakes and related phenomena
Earthquake: sudden release of energy resulting from the rapid movement between two blocks of rock
Body Waves
Surface Waves: like ocean surface
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Seismology: study of earthquakes and related phenomena
Body Waves:
P-Waves
Primary waves
S-Waves
Secondary waves
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Seismology: study of earthquakes and related phenomena
Surface Waves (similar to ocean waves):
Direction of wave movement
Direction of particle movement
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Structure of the Earth
using seismology, the general structure of the earth can be determined
Moho
Moho: the boundary between the crust and the mantle
Upper mantle
Lower mantle
Metallic fluid
Metallic Solid
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Structure of the Earth
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml
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The Crust and Lithosphere
• Continental crust: thicker, less dense, older20 km (weathered areas) to 75 km (younger areas) thick
• Oceanic crust: thinner, more dense, more recent~7km thick
• Lithosphere: the crust and uppermost (rigid) mantle
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml
This system is dynamic, not static!
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The Crust and Lithosphere
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The Mantle
• asthenosphere: The relatively plastic layer of the upper mantle of the Earth on which the tectonic plates of the lithosphere move; small fraction of molten material
• Upper mantle, lower mantle: upper differs from lower in seismic wave velocity, but not clear what causes the difference
• Composition of mantle is similar to carbonaceous chondrites, the original nebular composition, except depleted in volatiles and iron
• Where did the volatiles and the iron go?
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The Core
• Mostly iron, ~6% nickel ~8-10% other materials
• More dense than the mantle
• Source of the earth’s magnetic field
• When a metal (conductor of electricity) undergoes convection, a magnetic field is created
• Over geologic time the polarity of the magnetic field shifts back and forth (North becomes South, and vice versa)
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II. Plate Tectonics
1. Sea Floor Spreading
2. Continental Drift
3. Plate Tectonics
4. Deep Earth Processes
5. The Rock Cycle
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Sea floor spreading: ocean topography
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Sea floor spreading: magnetic polarity and age
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Sea floor spreading: magnetic polarity and age
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Sea floor spreading: magnetic polarity and age
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Pangea
Continental Drift and Pangea
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Plate Tectonics: plates and plate boundaries
Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)
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Plate Tectonics: plates and plate boundaries
Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)
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Plate Tectonics: plates and plate boundaries
Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)
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Plate Tectonics: plates and plate boundaries
Types of boundaries, or margins:
a) Divergent: plates moving away from each other
b) Convergent: plates moving towards each other
c) Transform: plates slipping past each other
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Plate Tectonics: plates and plate boundaries
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Plate Tectonics: plates and plate boundaries
Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)
passive margin
transform margin
convergent margin
divergent margin
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http://neic.usgs.gov/neis/plate_tectonics/plates.html
Plate Tectonics: plates and plate boundaries
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http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml
Deep Earth Processes
1. Heat
• Radioactive decay
• Gravitational energy released during accretion and formation of
earth
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Deep Earth Processes
2. Mantle convection
Not sure exactly how the convection occurs
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Deep Earth Processes
3. How they affect plate movement: Gravitational forces associated with density differences, due to hot less-dense magma from mantle
less densemore dense
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The Rock Cycle: igneous rocks
• Rock Types: Igneous, sedimentary, metamorphic
• Igneous: cooling and solidification of magma that upwells from the mantle in mid-ocean ridges; all rocks originate from igneous
• Ocean lithosphere: average age 80 M yrs; max age 200 M yrs
• Continental lithosphere: max age 4 B yrs; parts of the continent that became tectonically dormant and now reside in the middle of continents, called cratons
• Why is the maximum age of the ocean crust so much less than the maximum age of the continental crust?
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The Rock Cycle: cratons
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• Weathering: decomposition of exposed rocks into finer material called sediments and dissolved into water
• Weathering caused by physical, biological, and chemical forces
• Erosion: transport of sediments and dissolved material by wind, landslides, and streams to basins in the ocean or on land
• Erosion forms landscapes: more resistant material is not eroded, leaving landforms such as peaks and ridges
The Rock Cycle: weathering, erosion, & sediments
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• Sediments overly much of the oceanic and continental crust. Ocean sediments: sediments that were washed in through rivers, as well as shells from plankton near the ocean surface, that settle through the water column and settle on the ocean floor.
Continental sediments: from weathering on mountains, sediments accumulate in low lying basins; also, largely from former ocean floors that were transported, exposed, and uplifted due to tectonic activity
• Sediments are deposited in layers, accumulating through time; as the depth increases, temperature and pressure increases
• Lithification: Sediments are compacted into sedimentary rocks
The Rock Cycle: sediments and sedimentary rocks
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http://neic.usgs.gov/neis/plate_tectonics/plates.html
Plate Tectonics: plates and plate boundaries
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• uplift: due to continental collisions, former low-lying surfaces are forced up creating mountains and plateaus
• As soon as higher areas are formed, weathering and erosion begins
• In general, higher mountain ranges are younger, having experienced less erosion
• Subduction: sediments deposited in subduction zones are transported into the earth’s mantle; igneous rocks that were never eroded also enter subduction zones
• Metamorphism: subducted material undergo intense heat and pressure, are transformed into magma in the upper mantle, eventually to re-surface through mid-ocean ridges
The Rock Cycle: uplift, subduction, and metamorphism
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The Rock Cycle
Kump et al. system diagram
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The Rock Cycle
Mountains (all types)
Sedimentary Basinserosion,
sedimentation
Subduction Zone (all types)
subduction
Aesthenosphere (metamorphic)
metamorphism
Sea floor (igneous)
extrusion, volcanism
uplift
Frei system diagram
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml
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