Presentation on theme: "Dynamic Earth This unit will cover: layers of the earth, plate tectonics, volcanoes, earthquakes."— Presentation transcript:
Dynamic Earth This unit will cover: layers of the earth, plate tectonics, volcanoes, earthquakes
Earth’s Internal Structure: Compositional Layers 1. Crust: u Continental crust u Oceanic crust 2. Mantle Largest section Includes the asthenosphere toward the top Solid part and semi-liquid parts to it 3. Core n Inner core (Solid—Iron) n Outer Core (Liquid)
The Lithosphere contains the crust and the solid mantle
Early observations of the world Alfred Wegener proposed an idea for CONTINENTAL DRIFT. Continental Drift= proposed that the world’s continents were stuck together He called his super continent PANGEA.
Rejected….. Alfred Wegener idea of Pangea was rejected after his death in 1930. The use of Seafloor spreading was a new idea that was promoted.
Technology used in Seafloor Spreading Sonar—uses sound waves to measure the depth of the bottom of the ocean Magnetometer—is a device to measure the changes in magnetic fields. Antarctic- using magnetometer Sonar
Results… Map Generated Topographical Maps that showed the deep sea trenches and ocean ridges. Picture of California’s Coast Blue—water Green, brown-- land
Theory of Plate Tectonics Which states that the Earth’s crust and rigid upper mantle is broken into plates The plates move in different directions and different rates over time.
Plate Boundaries Divergent Boundaries –Places where plates are coming apart Convergent Boundaries –Places where plates crash or crunch together Transform Boundaries –Places where plates slide past each other
Divergent Boundary –Places where plates are coming apart
Convergent Boundary With Subduction Plate Plates crash into each other
Transform Boundary –Places where plates slide past each other
Most destructive forces on Earth. But it is buildings and other human structures that cause injury and death, not the earthquake itself 1988 - Soviet Armenia: magnitude 6.9, 25,000 people died 1985 - Mexico City: magnitude 8.1, 9500 people 1989 - Loma Prieta, CA: magnitude 7.1, 40 people died 1995 - Kobe, Japan: magnitude 7, ~6000 people died
Where do earthquakes occur? They occur when plates are diverging, sliding past each other, colliding or going underneath each other. There are three types of faults –Strike-Slip Fault –Normal Fault –Reverse Fault Thrust Fault
Body Waves P waves: Pressure or compressional waves. Vibrate parallel to direction of wave travel like a slinky. Fast travel: 4-7 km/sec (15,000 mph) P is primary, or first wave to arrive at recording station S waves: Shear waves. Vibrates perpendicular to direction of wave travel. Like snapping a rope Slower than P wave: 2-5 km/sec (11,000 mph) So S is secondary, or second wave to arrive at recording station
Locating the Epicenter of an Earthquake P, S and surface waves all start out at same time. The further you are away from the quake, the longer the time span between arrival of P and S wave. The distance of the seismometer to the earthquake can be determined by the time between the arrival of P wave and arrival of S waves. Can tell the distance, but not the direction. Therefore, multiple sites must be used to find epicenter.
Hot Spots Islands associated with hot spots (island chains, mid-ocean ridges, triple junctions). Iceland (mid-ocean ridge). Galapagos Islands (triple junction). Island of Hawaii (mid-plate volcanic chain; hot spot trace). Linear island chains form as plate moves over hot spot. Hawaiian islands get older in direction of plate movement (older away from mid-ocean ridge).
Volcanoes Basic parts of a volcano Crater (depression at the summit of a volcano, connected by a vent or pipe to the magma chamber below) Caldera (crater more than 1 km in diameter, formed at the summit of a volcano when lava is drained from an underground magma chamber, causing the summit of the volcano to be unsupported, and to collapse)
Example of Caldera Crater Lake in Oregon. This volcano was so violent that the top of the mountain was blown off. Now all is left is a beautiful lake.
Pit crater (collapse features on the flanks or summit of a volcano that are smaller than the main caldera at the summit of a volcano) Vent (pipe-like conduit from the magma chamber to the surface) Fumaroles (secondary vents on the flank of a volcano which emit steam and other gases)
Types of Volcanoes 1. Shield volcanoes - Hawaii Docile lava outpouring. Only minor pyroclastic material Lava forms broad dome with central crater Slope is 2-10 degrees, like flattened shield Very long lived, very large, massive amounts of lava (pahoehoe and aa) Example: Kilauea
Mauna Loa, on the Big Island of Hawaii, is the largest active volcano in the world. It last erupted in 1984. Mauna Loa erupted 14 times in the 20th Century, and 37 times since 1832. Mauna Loa is the most massive mountain on Earth, rising to an elevation of 13,677 feet above sea level, or 31,677 feet above the sea floor. Its volume is 10,000 miles 3.
2. Cinder cones Erupt pyroclastic material Steep slopes (30 to 40 degrees) Not very long lived. Typically small, less than 1000 feet tall Often parasitic on larger volcanoes Examples: Mt. Shasta
3. Composite volcanoes Erupt lava and pyroclastic material Intermediate slopes because lava acts like protective coating on pyroclastic layers Built up over long periods of time Most picturesque, but most violent Examples: Mt. Vesuvius, Mt. Fuji, Yellowstone
Eruption of Mount Saint Helens, May 18, 1980 The eruption of Mount Saint Helens was the most destructive in the history of the United States The eruption of Mount Saint Helens was the most destructive in the history of the United States Mount Saint Helens is located in southwest Washington in the Cascade Range, a mountain range dominated by periodically active volcanic peaksIn Mount Saint Helens is located in southwest Washington in the Cascade Range, a mountain range dominated by periodically active volcanic peaksIn Images include pre-eruption activity and post- eruption effects such as the blast area, mud flows, ash fall, and altered terrain Images include pre-eruption activity and post- eruption effects such as the blast area, mud flows, ash fall, and altered terrain http://www.ngdc.noaa.gov/seg/hazard/slideset/31/31_thumbs.html http://www.ngdc.noaa.gov/seg/hazard/slideset/31/31_thumbs.html http://www.ngdc.noaa.gov/seg/hazard/slideset/31/31_thumbs.html