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Geology Earth’s Interior, Plate Tectonics, Earthquakes & Volcanoes Earth’s Interior 1.Earth’s interior is divided into the: a. Crust b. Mantle c. Outer core d. Inner core surface center of earth 2. The lithosphere includes the crust and the rigid upper layer of the mantle. 3. The asthenosphere lies below the lithosphere and is made up of the soft layer of the mantle. Earth’s Interior Plate Tectonics 1. Plate – lithosphere is broken into separate sections called plates 2. Alfred Wegener developed the idea that the continents were once joined and have since drifted apart. The once giant land mass was known as Pangaea. 3. The Theory of Plate Tectonics explains the plates constant, slow motion, driven by convection currents in the mantle. It combines the theories of continental drift and sea-floor spreading. Sea-Floor Spreading Diagram Sea-Floor Spreading is the process by which molten material adds new oceanic crust to the ocean floor driven by convection currents in the mantle. C A = Molten magma rising –Mid-Ocean Ridge forming B = Sea-Floor spreading by convection currents C= Convergent Boundary leading to subduction – trench forming Plate Tectonics a. Plates move in the following ways: i. Transform Boundaries - slip past one another/No change in elevation (stress = shearing) ii. Divergent Boundaries - move apart/may cause a change in elevation (stress = tension); found at mid-ocean ridges; created by sea-floor spreading (2 oceanic plates); can create a rift valley on Earth when 2 continental plates move apart. iii. Convergent Boundaries - come together/may cause a change in elevation (stress = compression); 2 oceanic plates or 1 oceanic plate & 1 continental plate converge – subduction occurs and a trench is formed; 2 continental plates converge – a mountain is formed Plate Tectonics/Plate Boundaries Diverging Plate Boundary Converging Plate Boundary Transform Plate Boundary Earthquakes A. Description 1. An earthquake is the shaking and trembling that results from the movement of rock beneath Earth’s surface 2. Earthquakes occur because of stress built up in rock. Stress is a force that acts on a rock to change its shape or volume. These stresses cause faults (a break or crack in Earth’s lithosphere (underground) along which the rocks move). There are three types: a. Shearing – Strike-slip Fault b. Tension – Normal Fault c. Compression – Reverse Fault Plate Tectonics & Faults Tension Normal Fault Compression Earthquakes B. Measuring Earthquakes 1. Seismic Waves – vibrations that travel through Earth carrying the energy released by an earthquake. a. Primary Waves – P waves arrive first move by compression and expansion b. Secondary Waves – S waves arrive second - move side to side and up and down c. Surface Waves – when P and S waves meet the surface – move in different directions 2. Epicenter – center of the earthquake ON Earth’s surface; in order to find the epicenter of an earthquake, you need data from 3 cities 3. Focus – the point UNDER ground where the Earth’s breaks under stress and causes an earthquake Earthquakes C. Earthquake Hazards 1. Soil Conditions/Shaking 2. Liquefaction – violent shakes turn loose, soft soil into mud 3. Aftershock – earthquake that occurs after a big earthquake in the same area 4. Tsunamis – large wave caused by an earthquake on the ocean floor D. Earthquake Safety 1. 2. 3. Location – some places are more prone to earthquakes Construction – earthquake-proof buildings/houses (base-isolated buildings) Drop, cover and hold E. Earthquake Detecting Devices – 4 fault monitoring devices 1. Creep Meters – uses a wire across a fault to measure horizontal movement of the ground 2. Laser-ranging Devices – uses a laser to measure horizontal movement 3. Tiltmeters – measures tilting or raising of the ground 4. Satellite Monitors – uses GPS from outer space to monitor changes in elevation as well as horizontal movement along a fault 5. Seismographs – collects data (seismic waves) from earthquakes Volcanoes A. Description 1. A volcano is an opening in Earth’s Surface where magma escapes from the interior. Magma is the liquid inside a volcano. When magma reaches earth’s surface it is called lava. 2. Most volcanoes occur near the boundaries of Earth’s Plates and along the edges of continents above subduction zones, in island arcs, or along mid-ocean ridges (under water mountain ranges) Earthquakes & Volcanoes Volcanoes B.Volcanic Landforms 1. Shield Volcanoes – Hawaiian Islands; quiet eruptions, lava flows, wide base, not very tall – usually created over hot spots 2. Cinder Cone Volcanoes – Paricutin in Mexico; explosive eruptions of cinders/rock/gases – tall, narrow base 3.Composite (Strato) Volcanoes – alternating quiet/explosive eruptions – alternating layers of lava and ash; Mt. Hood, Mt. St. Helen’s, Mt. Ranier – usually created at subduction zones Volcanoes C. Volcano hazards 1.Pyroclastic flows 2.Damage from ash 3.Lava Flows 4.Avalanches of mud 5.Flooding 6.Deadly gases Volcanoes D.Volcano Benefits 1. Fertile Soil 2. Increased Tourism 3. Energy source