Earth Systems Science Chapter 7

1. Earth Systems ScienceChapter 7 • Structure of the Earth • 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).

2. Earth Systems ScienceChapter 7 I. Structure of the Earth • Seizmology, structure of the earth • The crust and lithosphere • The mantle • The core

3. Surface Waves: like ocean surface Body Waves Seismology: study of earthquakes and related phenomena Earthquake: sudden release of energy resulting from the rapid movement between two blocks of rock

4. P-Waves Primary waves S-Waves Secondary waves Seismology: study of earthquakes and related phenomena Body Waves:

5. Direction of wave movement Direction of particle movement Seismology: study of earthquakes and related phenomena Surface Waves (similar to ocean waves):

6. Moho Upper mantle Lower mantle Structure of the Earth using seismology, the general structure of the earth can be determined Moho: the boundary between the crust and the mantle Metallic fluid MetallicSolid

7. Structure of the Earth http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml

8. This system is dynamic, not static! 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

9. The Crust and Lithosphere

10. 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?

11. 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)

12. II. Plate Tectonics • Sea Floor Spreading • Continental Drift • Plate Tectonics • Deep Earth Processes • The Rock Cycle

13. Sea floor spreading: ocean topography

14. Sea floor spreading: magnetic polarity and age

15. Sea floor spreading: magnetic polarity and age

16. Sea floor spreading: magnetic polarity and age

17. Pangea Continental Drift and Pangea

18. Plate Tectonics: plates and plate boundaries Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)

19. Plate Tectonics: plates and plate boundaries Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)

20. Plate Tectonics: plates and plate boundaries Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)

21. Plate Tectonics: plates and plate boundaries Types of boundaries, or margins: Divergent: plates moving away from each other Convergent: plates moving towards each other Transform: plates slipping past each other

22. Plate Tectonics: plates and plate boundaries

23. passive margin convergent margin transform margin divergent margin Plate Tectonics: plates and plate boundaries Periods of statis (stress builds up between plates)Periods of movement (stress is released, earthquakes)

24. Plate Tectonics: plates and plate boundaries http://neic.usgs.gov/neis/plate_tectonics/plates.html

25. Deep Earth Processes 1. Heat • Radioactive decay • Gravitational energy released during accretion and formation of earth http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml

26. Deep Earth Processes 2. Mantle convection Not sure exactly how the convection occurs

27. less dense more dense Deep Earth Processes 3. How they affect plate movement: Gravitational forces associated with density differences, due to hot less-dense magma from mantle

28. 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?

29. The Rock Cycle: cratons

30. The Rock Cycle: weathering, erosion, & sediments • 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

31. The Rock Cycle: sediments and sedimentary rocks • 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

33. Plate Tectonics: plates and plate boundaries http://neic.usgs.gov/neis/plate_tectonics/plates.html

34. The Rock Cycle: uplift, subduction, and metamorphism • 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

35. The Rock Cycle Kump et al. system diagram

36. 1 The Rock Cycle http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Inside.shtml Mountains (all types) Sedimentary Basins 2 5 erosion, sedimentation subduction uplift Subduction Zone (all types) Sea floor (igneous) Frei system diagram 4 Aesthenosphere (metamorphic) metamorphism extrusion, volcanism 3