Chapter 3 The Dynamic Earth Section 1 The
- Slides: 26
Chapter 3 – The Dynamic Earth Section 1: The Geosphere 1. Describe the composition & structure of the Earth 2. Describe the Earth’s tectonic plates 3. Explain the main cause of earthquakes & their effects 4. Identify the relationship between volcanic eruptions & climate change 5. Describe how wind & water alter the Earth’s surface
The Earth as a System • Earth consists of rock, air, water, & living things that interact with each other AIR • Divided into 4 parts: WATER LIVING THINGS ROCK
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
Discovering Earth’s Interior • Seismic waves used to study interior of Earth • Seismic waves Earthquake – Travel through Earth’s interior during earthquakes – Altered by type of material they move Seismic – Changes in speed & wave direction measured when passing through different layers
Composition of the Earth • Divided into three layers based on composition – Crust – Mantle – Core • layers become progressively denser toward the center Crust Core Mantle
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
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
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
The Structure of the Earth • Divided into 5 layers based on the physical properties Lithosphere Asthenosphere Mesosphere Outer Core Inner Core
Lithosphere • Composes crust & upper part of mantle – 15 -300 km thick (9185 mi) • Divided into large pieces called tectonic plates – May be oceanic or continental – Slide on fluid portion of mantle – Movement can cause earthquakes
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
Mesophere • Lower part of mantle • More solid & rigid than asthenosphere due to increased pressure – Can’t flow Lithosphere Asthenosphere Mesosphere Outer Core Inner Core
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
Inner Core • Solid ball • Composed of nickel & iron • 9000 °F & 45, 000 psi • Rotates in liquid outer core
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
Major & Minor Tectonic Plates move in different directions and speeds, thus crash together, pull apart or side swipe each other like cars in a demolition derby
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
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
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
Where Earthquakes Occur Most occur at or near plate boundaries
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
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
Volcanoes: The Ring of Fire North American Plate Eurasian Plate South American Plate • Majority of active volcanoes on land located along tectonic plate surrounding the Pacific Ocean Pacific Plate Australian Plate Antarctic Plate
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
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
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
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