Chapter 3 – The Dynamic Earth Section 1: The Geosphere

1. Chapter 3 – The Dynamic EarthSection 1: The Geosphere Describe the composition & structure of the Earth Describe the Earth’s tectonic plates Explain the main cause of earthquakes & their effects Identify the relationship between volcanic eruptions & climate change Describe how wind & water alter the Earth’s surface

2. The Earth as a System • Earth consists of rock, air, water, & living things that interact with each other • Divided into 4 parts: AIR WATER LIVING THINGS ROCK

3. The Earth as a System • Geosphere • Solid portion consisting of rock • Extends from center of core to surface of crust • Atmosphere • Mixture of gases • Most found in first 30 km above Earth’s surface • Hydroshpere • All water on or near surface • Most is oceans • Biosphere • Where life exists • Extends from 9 km above surface to bottom of ocean

4. Discovering Earth’s Interior • Seismic waves used to study interior of Earth • Seismic waves • Travel through Earth’s interior during earthquakes • Altered by type of material they move • Changes in speed & direction measured when passing through different layers Earthquake Seismic wave

5. Composition of the Earth Crust • Divided into three layers based on composition • Crust • Mantle • Core • layers become progressively denser toward the center Core Mantle

6. Crust • Thin, outermost layer • 5 to 8 km beneath oceans • 20 to 70 km beneath continents • Solid, brittle • Composed of lightweight elements • Makes up less that 1% of Earth’s mass

7. Mantle • Layer between crust & core • Composed of rock with medium density • Contains iron-rich minerals • Makes up 64% of Earth’s mass • Approximately 2900 km thick

8. Core • Innermost layer • Liquid outer core • Super-heated molten lava • Composed of liquid nickel & iron • Solid inner core • Sphere of solid nickel & iron • Consists of densest elements • Radius approximately 3400 km Solid inner core

9. The Structure of the Earth • Divided into 5 layers based on the physical properties Lithosphere Asthenosphere Mesosphere Outer Core Inner Core

10. Lithosphere • Composes crust & upper part of mantle • 15-300 km thick (9-185 mi) • Divided into large pieces called tectonic plates • May be oceanic or continental • Slide on fluid portion of mantle • Movement can cause earthquakes

11. Asthenosphere • Beneath lithosphere • 250 km thick (150 mi) • Solid, plastic-like material of mantle • Made of rock that flows • Due to temperature & pressure • Allows for movement of tectonic plates

12. Mesophere • Lower part of mantle • More solid & rigid than asthenosphere due to increased pressure • Can’t flow Lithosphere Asthenosphere Mesosphere Outer Core Inner Core

13. Outer Core • Super-heated molten lava • Composed of liquid nickel & iron • 4000 to 9000 °F • Source of Earth’s magnetic field • Creates protective bubble • Deflects Sun’s solar winds

14. Inner Core • Solid ball • Composed of nickel & iron • 9000 °F & 45,000,000 psi • Rotates in liquid outer core

15. Plate Tectonics • Large, irregularly shaped slabs of rock • Composed of oceanic & continental lithosphere • Continental rocks • Lightweight minerals (quartz, feldspar) • Thicker crust • Oceanic rocks • Heavier, denser basltic rocks • Thinner crust

16. Major & Minor Tectonic Plates Plates move in different directions and speeds, thus crash together, pull apart or side swipe each other like cars in a demolition derby

17. Plate Boundaries • Most geologic activity occurs where plates meet or divide (called boundaries) • Movement of plates creates 3 types of tectonic boundaries • Convergent – plates collide, move into one another • Divergent – plates move apart • Transform – plates move sideways in relation to one another • Movement of tectonic plates causes • Mountain formation • Earthquakes • Volcanic eruptions

18. Plate Tectonics and Mountain Formation • Plates collide, crust thickens • Rocks break & buckle • Continental plate folds into huge mountain • Oceanic plate forms trench • Examples • Rocky mountains (N. America) • Himalaya mountains (Central Asia

19. Earthquakes • Faults – breaks in Earth’s crust where plates slide past each other • Rocks under stress break off triggering ground vibrations - called earthquakes • Magnitude (Richter Scale) • Measure of energy released • 2.0 – smallest felt • 9.5 – largest recorded • Increase of 1 whole number = 31.7 times more energy

20. Where Earthquakes Occur Most occur at or near plate boundaries

21. Earthquake Hazard • Earthquake hazard level determined by past & present seismic activity • Hazards (effects) include • Ground shaking (building damage/settling of ground beneath to different level) • Ground displacement • Flooding (breakage of levies, dams, Tsunamis) • Fire (broken gas & power lines) • Human hazards due to man-made structures • Being crushed, buried or burned or drowning • National Hazards Maps used by cities, counties & local governments to update & create more stringent building codes

22. Volcanoes • Mountains built from magma (molten rock) • Magma rises to surface from interior • Most common at convergent or divergent plate boundaries • Can occur on land or in oceans Block between separating faults cracks, drops into asthenosphere forming a rift. Magma seeps upward to fill in crack

23. Volcanoes: The Ring of Fire • Majority of active volcanoes on land located along tectonic plate surrounding the Pacific Ocean North American Plate Eurasian Plate South American Plate Pacific Plate Australian Plate Antarctic Plate

24. Local Effects of Volcanic Eruptions • Clouds of hot ash, dust, & gases flow down the slopes of volcanoes searing anything in its path • Obscures sunlight, killing plants & animals • Volcanic ash mixes with water producing mudflows • Water contamination • Land contamination • Collapse of buildings, burying of crops, & damage to vehicle engines due to falling ash

25. Global Effects of Volcanic Eruptions • Can cause changes in Earth’s climate • Ash & sulfur-rich gases reach upper atmosphere & reduce sunlight reaching Earth’s surface • Reduction in sunlight reduces average global temperatures

26. Erosion • Process resulting in materials of the Earth’s surface being loosened, dissolved or worn away & transported from one place to another by natural agents such as wind, water, ice or gravity • Water erosion • Rivers carve deep canyons or gorges into bedrock • Depositing of dust, pebbles, rocks forms new land areas • Oceans erode coastlines • Wind erosion • Removal of most fertile part of soil lowering soil productivity • Creates sand dunes