1. 1 Environmental Science Unit 1: Geology Basics Earth’s Layers & Plate Tectonics

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3. 3 Lithosphere vs Asthenosphere Lithosphere: Crust + upper Mantel Lithosphere: Crust + upper Mantel –80 km deep (50 miles) –Less dense than Asthenosphere –Floats on the Asthenosphere –Plates move slowly! 2”/yr Asthenosphere: Asthenosphere: –Fluid part of Mantel—ductile, like putty –Underneath the Lithosphere

4. 4 Shape of Earth’s Surface Main force: Movement of Earth’s outer layer by the process of: Main force: Movement of Earth’s outer layer by the process of: –PLATE TECTONICS What is a “tectonic plate”? What is a “tectonic plate”? –Earth’s crust is made up of ~12 “plates” that fit together like a jigsaw puzzle. Plates have continental and ocean crust. Plates have continental and ocean crust. Plates move around, causing: Earthquakes, Volcanoes, Mountain Building, and much of the Rock Cycle. Plates move around, causing: Earthquakes, Volcanoes, Mountain Building, and much of the Rock Cycle.

6. 6 Processes that change Earth’s surface: Weathering & Erosion Weathering & Erosion –Weathering Chemical Chemical Physical Physical –Wind –Water Volcanism Volcanism Deformation Deformation

7. Plate Movements Converging Plates – plates moving together, form trenches Converging Plates – plates moving together, form trenches Diverging Plates – Plates moving apart, form mid-oceanic ridges Diverging Plates – Plates moving apart, form mid-oceanic ridges 7

8. 8 What is “Subduction” ? Two sections of crust collide Two sections of crust collide –One slab is forced down deep into Earth

9. 9 Volcanism Bring Magma to the surface Bring Magma to the surface

10. 10 Volcanism The most general cause of volcanism on earth is Subduction of earth’s crust. The most general cause of volcanism on earth is Subduction of earth’s crust. –One tectonic plate is forced under another plate as the plates push together.

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12. 12 Mid-Ocean Ridges Bottom of sea splits apart: Bottom of sea splits apart: –Magma rises –New Crust formed “Spreading Ridges” “Spreading Ridges” –Lithosphere slides away from elevated region 4 cm/yr 4 cm/yr –Central portions of oceans

13. Rifting Continents can also split apart at “rifts”. Continents can also split apart at “rifts”. –Continued rifting can form a new ocean.

14. Chemical Weathering Minerals in rocks are dissolved into rainwater or changed from one type of mineral into another. Minerals in rocks are dissolved into rainwater or changed from one type of mineral into another. Occurs most readily in warm, moist areas. Occurs most readily in warm, moist areas. –Warm speeds up chemical reactions. –Water is required for chemical weathering. Minerals differ in their resistance to chemical weathering. Minerals differ in their resistance to chemical weathering. –Quartz resists chemical weathering. –Feldspar does not resist well. Breaks down into clay minerals. Breaks down into clay minerals.

15. 15 Chemical Weathering Ever been to a cave? Ever been to a cave? –Caverns develop as water flows underground, dissolving minerals in rock and transporting them away. Cave features, such as stalactites and stalagmites form when mineral-carrying water drips and leaves behind some of its mineral load. Cave features, such as stalactites and stalagmites form when mineral-carrying water drips and leaves behind some of its mineral load.

16. Cave Stalactites “Hang on tight” to the ceiling. Stalactites “Hang on tight” to the ceiling. –Form as minerals come out of water as a drip forms. “Mighty” Stalagmites “Mighty” Stalagmites –Form as minerals come out of water after it drips to the floor.

17. Physical Weathering Rocks are broken apart into smaller pieces by water and other forces. Rocks are broken apart into smaller pieces by water and other forces. –Moving liquid water can break rock apart by knocking rocks together. Rivers, Ocean surf, etc. Rivers, Ocean surf, etc. –Glaciers break, grind, and move rock. –Water can break rock as it freezes in cracks. Water expands as it freezes, and can exert tremendous forces. Potholes in roads and exploding soda cans show the power of freezing water. Water expands as it freezes, and can exert tremendous forces. Potholes in roads and exploding soda cans show the power of freezing water.

19. 19 Soil Bits of broken rocks + remains of plants & animals Bits of broken rocks + remains of plants & animals

20. Soil Soil Horizon – Each Soil Horizon – Each layer of soil in a soil profile profile Soil Profile – The Soil Profile – The arrangement of the layers of soil in an area 20

21. 21 What is a “Fault” ? Fracture due to stress on rock Fracture due to stress on rock Cause: pushing & shoving of crust: Cause: pushing & shoving of crust: –Seafloor spreading

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23. 23 Making Mountains

24. 24 Making Mountains Folding Folding –Colliding plates—neither is subducted –Plates crash and rise vertically