Earth

1. Earth The Dynamic Planet

2. Earth’s Interior Courtesy of the USGS

3. Core The core is differentiated into an innersolid region and an outer liquid region.Both regions are composed mostly ofiron and nickelInner core is not solidly tied to rest ofEarth, and is free to rotate Diagram from USGS Earth’s magnetic field created by electrically conductive fluidflowing past magnetic field, which creates an electric current; current strengthens the magnetic field

4. Mantle Mantle is composed mostly of siliconThought to exhibit a plastic behavior; solid on short time scales, liquid over long timescales Diagram from the USGS Differences in temperature between core and crust cause mantle to convect; this convection drives movement at the surface

5. Crust Crust is mostly SiO2Two types of crust: oceanic and continental crustOceanic crust is thinner and denser; darker in color;basaltic (only about 50% silicate) Continental crust is thicker and less dense; lighter in color;granitic (about 70-80% silicate) Diagram from USGS

6. Seismology Surface waves - Travel along the Earth’s surface, do not penetrate the crust, slowest wave speed Compressional body waves - particles move in direction of wave velocity, fastest wave speed; called P-waves Transverse body waves - particles move perpendicular tothe direction of wave velocity, slower than compressional,but faster than surface; also called shear waves since the particles will experience a shearing action;called S-waves

7. Seismology, cont. Use earthquakes to probe theinterior of the EarthWaves travelling through the Earth are refracted (bent) and reflected depending upon theirproperties and those of the different layers of the Earth S-Wave shadow zone

8. Plate Tectonics Originally conceived of as continental drift by Wegener; he noticed similarities in coastlines, fossil record, rock layers, and glacial scarring Modern satellite technology allows us to measure the relative movement of the plates

9. Plate Boundaries Divergent - Plates move apart from each other Convergent - Plates move toward each other Transform - Plates move parallel to the boundary in opposite directions

10. Divergent Plate Boundaries • Start as rift valleys • Basaltic, high density magma wells up from the mantle-crust interface to replace rock • New crust that forms is thinner and denser; as it cools, it sinks lower than the surrounding continental crust • Ocean water eventually fills in between the two continents

11. Convergent Plate Boundaries If oceanic crust collides withcontinental crust, oceanic crust goesunder (subduction zone), melts, andresurfaces as an island arcEx. New Zealand, Aleutian Islands If two continental plates collide, crustal material “piles up” and a mountain chain is developed Ex. Himalayan Mountains

12. Transform Plate Boundary As plates move past one another, friction causes sides to stick together While sides are stuck, stress builds between the plates When stress gets high enough, sides violently slide past one another  Photograph by Robert E. Wallace, USGS Loma Prieta Earthquake, 1989, Courtesy of the USGS

13. Rock Types Constant plate movement drives the rock cycle Three different types of rock are igneous, metamorphic, and sedimentary

14. Igneous Rock formed from a molten state Type of igneous rock determined by 1) type of magma from which rock cools and 2) location where rock cools Volcanic - extrusive; magma cooled at the surface; smaller crystals Plutonic - intrusive; magma cooled below the surface; larger crystals

15. Sedimentary Formed from sediment that is cemented together Type of rock depends upon 1) size of sediment and 2) origin of sediment Photo of Canyonlands National Monument by Pratte Two Types Clastic - broken rock and mineral that are cemented together Ex.: sandstone, shale, conglomerate Chemical - minerals that precipitate out of solution Ex.: limestone, chalk

16. Metamorphic Formed from other rocks by changing mineralogy or texture without passing through a molten state • Change occurs because of one or more of the following • parameters: • pressure - causes rock crystals to change orientation and structure (Ex. gneiss) • temperature - induces different chemical bonds without melting(Ex. hornfels) • chemically reactive fluid - minerals in the fluid replace mineralsin the rock (Ex. petrified wood) or form new bonds

17. Rock Cycle Processes like weathering, erosion, and plate tectonics change the rock from one form to another Rock can be transmuted from any form to any other form’ by these processes Example: An igneous rock that is brought to the Earth’s surface is weathered and eroded. Sediment pile is buried, causing cementation into a sedimentary rock. Further burial creates pressures strong enough to change chemical bonds, creating a metamorphic rock.

18. Soil Types Soil - a mixture of organic andinorganic sediments found on the Earth’s surface; comprised of different layers O horizon - consists of decomposing organic matter; might be missing A horizon - comprised of a mixture of organic and inorganic matter E horizon - light colored, acidic layer found in evergreen forests B horizon - brown or red layer enriched in clay, iron, and/or aluminum K horizon - enriched with calcium carbonate; found in arid regions C horizon - lowest layer comprised almost entirely of inorganic rock sediment

19. Soil Forming Factors Different horizons occur at different locations for many reasons Some factors: • Climate - temperature, precipitation, and wind affect weathering,erosion, vegetation, and decomposition of organic matter • Local rock - provides the inorganic material for soil • Topography - steeper slopes mean more erosion • Vegetation - holds soil in place; provides the organic material for soil • Time - more mature soils have had elements working on it longer • Mankind - our activities affect erosion and soil nutrients

20. Weathering and Erosion Weathering - the breaking apart of rocks either physically orchemically Erosion - the removal of sediment from a location; can occur by water, wind, landslide, etc.; enhanced by mankind’s disturbances