Earth’s Structure by Brainpop Geological Changes—3:25 Looking at the world map, what do you notice about the shape of the continents? Jot down.
Download ReportTranscript Earth’s Structure by Brainpop Geological Changes—3:25 Looking at the world map, what do you notice about the shape of the continents? Jot down.
Earth’s Structure by Brainpop Geological Changes—3:25 Looking at the world map, what do you notice about the shape of the continents? Jot down your ideas on your paper… The thing is…the world didn’t always look like this! It used to look like this: During its early years, the earth's outer layer was much hotter than it is today. Over time, the surface of the earth cooled and hardened. Cracks formed in the hardened surface, creating huge plates of rock. Plate Tectonics Theory The lithosphere is divided into a number of large and small plates and the plates are floating on the mantle Lithosphere = the Earth’s crust plus the upper portion of the mantle layer Where the edges of those plates meet, the huge slabs bash into each other, grinding, rumpling, scraping, and generally shoving each other around. We experience the more dramatic of these encounters as earthquakes http://earthquake.u sgs.gov/earthquak es/recenteqsus/ http://earthquake.usgs.gov/earthquakes/re centeqsww/ How is this possible?!?!? Plate motion based on The Global Positioning System (GPS) Divergent Boundaries Create Different Shapes on Earth Plate Boundaries Divergent boundary: o Plates are moving away from each other o Midocean ridges are created and new ocean floor plates are created Plate Boundaries Divergent boundary: http://library.thinkquest.org/17701/high/tect onics/ptconv.html Leif the Lucky Bridge Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates. Divergent Boundary Although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level. The section of the ridge which includes the island of Iceland is also known as the Reykjanes Ridge. The average spreading rate for the ridge is about 2.5 cm per year.[ It is estimated that the Atlantic Ocean sea floor expands at a rate of 0.5 to 4 inches annually Divergent Boundary Mountain Ranges By length Mid-Atlantic Ridge - 65,000 km (40,389 mi)[1] Andes - over 7,000 km (4,350 mi) Rocky Mountains - 4,800 km (2,983 mi) Great Dividing Range - 3,700 km (2,299 mi) Transantarctic Mountains 3,500 km (2,175 mi) Himalayas - approximately 2,400 km (1,491 mi) Divergent Boundary Rock outcrop in Iceland, a visible surface feature of the Mid-Atlantic Ridge, the Easternmost edge of the North American plate. It is a popular destination for tourists in Iceland. Divergent Boundary Animation During an earthquake at a divergent fault line, tectonic plates separate. In many cases, magma rises from the mantle to fill in the gap or one plate slide down to fill in the space. These types of earthquakes usually occur in the ocean. http://library.thinkquest.org/03oct/00758/en/disaster/ea rthquake/faultlines.html Convergent Boundaries Create Different Shapes on Earth Plates Collide Convergent Boundary: plates are moving toward each other and are colliding http://library.thinkquest.org/17701/high/tectonics/ptconv.html Convergent Boundary • Plates collide. One plate pushes under the other. Convergent Boundaries in Oceans When two ocean plates collide: Produces trenches. Ocean trenches are deep valleys in the ocean floor. The Mariana Trench is the deepest part of the world's oceans, and the lowest elevation of the surface of the Earth's crust. Convergent Boundaries in Oceans The Mariana Trench is the deepest part of the world's oceans, and the lowest elevation of the surface of the Earth's crust. If Mount Everest, the highest mountain on Earth at 8,848 metres (29,029 ft), was set in the deepest part of the Mariana Trench, there would be 2,062 metres (6,765 ft) of water left above it. When ocean plates collide with other ocean plates In addition to trenches, ocean plates collide and can produce volcanic islands. Convergent Boundaries with Continents The ocean plate and continental plate collides. The ocean plate moves underneath the continental plate. This forces the land above to form a mountain range. Convergent Boundaries with Continents • Mountain ranges are created • (example: Himalayan Mountains) Himalayan Mountains Mountains 2:46 Convergent Boundaries Creates Different Shapes on Earth Examples • the collision between the Eurasian Plate and the Indian Plate that is forming the Himalayas. • northern part of the Pacific Plate and the NW North American Plate that is forming the Aleutian Islands. • the Nazca Plate beneath the South American Plate to form the Andes. • the Pacific Plate beneath the Australian Plate, and vice versa forming the complex New Zealand to New Guinea •collision of the Eurasian Plate and the African Plate formed the Pontic Mountains in Turkey. • Mariana Trench Transform Boundaries Create Different Shapes on Earth Transform Plate Boundary The plates may move in opposite directions or in the same directions but at different rates and frequent earthquakes are created (example: San Andreas Fault) Transform Plate Boundary Transform Plate Boundaries are locations where two plates slide past one another. The fracture zone that forms a transform plate boundary is known as a transform fault. Most transform faults are found in the ocean Transform Plate Boundary http://geology.com/nsta/transform-plateboundaries.shtml Transform Plate Boundary San Andreas Fault The San Andreas fault is the 800 mile long boundary between the Pacific and North American Plates. It is the main fault of an intricate network of faults spanning the California coastal region. At its deepest, the San Andreas extends 10 miles beneath the ground. Transform Plate Boundary The San Andreas fault is a right-lateral transform fault meaning that if one was to stand on one side of the fault and look across to the other, the opposite site would appear to move to the right. This means the Pacific Plate is moving northward while the North American Plate is moving southward. http://library.thinkquest.org/03oct/00758/en/disaster/earthquak e/faultlines.html Plate Tectonics Theory Plate Tectonics Plate Tectonics Map - Plate Boundary Map http://geology.com/plate-tectonics.shtml So is the Earth getting bigger? o No o Transform boundaries neither create nor destroy lithosphere o Land is created with divergent boundaries but is destroyed with convergent boundaries. How can Oreos model the plate boundaries? Very carefully, take just the top cookie off the Oreo. Break the top cookie into 2 equal halves. Replace the cookie halves back on the Oreo Using the cookie, Demonstrate a transform fault boundary Demonstrate a divergent plate boundary Demonstrate a convergent plate boundary Seafloor Spreading Theory: • Ocean floors are moving like broad conveyor belts • New ocean floor crust is being created at the midocean ridges What causes this? Convection currents within the mantle The up-welling leg of the current creates a divergent boundary which produces midocean ridges Convection Current Demo The down-welling leg of the current creates one type of convergent boundary that results in trenches and a subduction zone What evidence do we have to support this idea? o Midocean ridges are warmer than surrounding ocean floors o Active volcanoes on ridges, earthquakes on ridges o Midocean ridge rocks are younger than surrounding ocean floor rocks o Midocean ridge volcanoes are younger than volcanoes further away What evidence do we have to support this idea? o Ocean floor sediments are thin on the ridges and get thicker as the distance from the ridges increase o Polar reversal magnetism proves that the ocean floor is moving away from the ridges Speed of Spreading Atlantic Ocean – 2-3 cm/year South Pacific Ocean – 15-18 cm/year Seafloor Spreading The Seafloor is Spreading Clip—4:01 How Earth’s Structure Affects Plate Tectonics—5:43 Continental Drift Theory The continents have shifted their position over geologic time At one time all land masses were connected into one piece called Pangaea Continental Drift Theory 3—2:21 o Pangaea began to split apart 200 million years ago o Diagram Laurasia Pangaea Gondwanaland Pangaea—A History of the Continents: 2:23 North America Greenland Eurasia West G. East G. Africa S.America Antarctica Australia India The First Continents 4:57 USGS Plate Motions Clip Continents o The continents are like packages on the seafloor conveyor belt Evidence o High percentage fit of continents at the 500 fathom level Evidence o Minerals, fossils, and mountains on now different continents match if the continents were together The Mystery of Brachiosaurus (~3 min) Evidence o Glaciation patterns indicate a common ice cap at the South Pole Evidence o Paleomagnetism (magnetism of old rocks) indicate a common pole if the continents were all connected Plate Tectonics 2 –4:22 Plate Tectonics by Brainpop