Geology Earth s Interior, Plate Tectonics, Earthquakes & Volcanoes
Earth s Interior 1. Earth s interior is divided into the: a. Crust surface b. Mantle c. Outer core d. Inner core 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.
A = Molten magma rising Mid-Ocean Ridge forming B = Sea-Floor spreading by convection currents C= Convergent Boundary leading to subduction trench forming 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
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. Location some places are more prone to earthquakes 2. Construction earthquake-proof buildings/houses (base-isolated buildings) 3. 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
A. Description Volcanoes 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