Chapter 3 – The Dynamic Earth Section 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

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

The Earth as a System Geosphere Atmosphere Hydroshpere Biosphere 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 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

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

Crust Thin, outermost layer Solid, brittle 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 Consists of densest elements 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 Lithosphere Divided into 5 layers based on the physical properties Asthenosphere Mesosphere Outer Core Inner Core

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

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

Outer Core Super-heated molten lava Source of Earth’s magnetic field 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 & 45,000,000 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 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 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

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