The collision of India and Asia 30 million years ago uplifted continental areas into the Himalayas and the approach of Africa to Europe will soon (less than 50 million years) eliminate the Mediterranean, Baltic, and Black Seas and then form another great mountain chain. At depths of 100 to 300 km (asthenosphere layer), the lighter molten rocks force their way upward behind the subduction zone, forming a volcanic chain
The buildings that took the most damage were old masonry buildings that had not been retrofitted to withstand an earthquake, however many of them had been retrofitted and survived the earthquake. The quake released an amount of energy equal to a 100 gigaton bomb, according to Roger Bilham, professor of geological sciences at the University of Colorado
Introduction to Plate Tectonics
As work continued on both polarity reversals and mapping the magnetic patterns on the floor, scientists figured out that one way to explain the observations was to have a process where ocean crust was formed along the ridges moved out in a conveyor-belt like fashion. As a result of that work, the variety of structures in the ocean bottom were identified and mapped, including a 40,000 km long ridge system that encircles the planet (the ridge system is identified in the map above by the light shaded regions near away from the continents)
It formed when a huge glacial lake in the North Sea overflowed, causing a prehistoric mega-flood, which sent water surging into the basin between Britain and France and gouging through the hills of chalky rock connecting them. The lithosphere essentially "floats" on the asthenosphere and is broken-up into ten major plates: African, Antarctic, Australian, Eurasian, North American, South American, Pacific, Cocos, Nazca, and the Indian plates
Reading Quiz Resources Did you know? Did you know that earthquakes and volcanic eruptions do not happen in random places? Both are concentrated along the boundaries of tectonic plates and provide evidence for the theory of plate tectonics. Ironically, however, the question that incited ridicule for Wegener continues to launch heated debate today: What ultimately drives plate motion? Plates are constantly shifting and rearranging themselves in response to each other
BBC - GCSE Bitesize: Distribution
Earthquakes and volcanoes are most likely to occur either on or near plate boundaries.The map shows the world's tectonic plates and the distribution of earthquakes and volcanoes
But if these huge masses of crust are moving apart, what happens in the space left between them? Seafloor Spreading Divergent boundaries in the middle of the ocean contribute to seafloor spreading. While many are small and cause only minor trembling, the San Andreas Fault has also been the site of major events: the 1857 Fort Tejon earthquake, the 1906 San Francisco earthquake and fire, and the 1989 Loma Prieta earthquake
Plate Tectonics
This magma, which is highly mobile fluid rock, rises to the surface to form chains of volcanoes, typically about 200 km inland from the line of subduction. Nothing on Earth is permanent, because heat continuously flows from the hot interior to the cooler surface, and mantle convection provides the primary mechanism for that heat transfer
! Broad fractured swell ! Basaltic volcanism (new crust), earthquakes As oceanic lithosphere moved away from the ridge ! it cools ! it becomes denser and thicker ! it subsides
Continental Convergent Boundaries When oceanic plates collide with continental plates, the denser oceanic plate is forced under the lighter continental plate. Continental Convergent Boundaries When continental plates collide into one another, neither plate can subduct under the other because they are equally light and buoyant
Earth Floor: Plate Tectonics
Where a divergent boundary crosses the ocean floor, the rift valley is much narrower, only a kilometer or less across, and it runs along the top of a midoceanic ridge. As shown in the drawing above, when Earth's brittle surface layer (the lithosphere) is pulled apart, it typically breaks along parallel faults that tilt slightly outward from each other
Plate Tectonics, Earthquakes, and Volcanoes
Earth Continents showing the fit of South America and Africa Created with CAST's UDL Book Builder Plate Boundaries Where tectonic plates touch, they form what are called plate boundaries. The Rocky Mountains, west of Cheyenne, Wyoming are an example of a landform Created with CAST's UDL Book Builder Stucture of the Earth Structure of the Earth Before we discuss plate tectonics, we must first discuss the structure of the Earth
This usually occurs when two plates either ride over, or slide against each other, and the material at the edge of the tectonic plates deforms and ruptures at its weakest point. Image: The Fault of San Andreas As seen in the image above, the trees (they look like small dots) in the aerial view of San Andreas fault have been offset by the slipping of the plates
Geologists believe that, if spreading continues, the three plates that meet at the edge of the present-day African continent will separate completely, allowing the Indian Ocean to flood the area and making the easternmost corner of Africa (the Horn of Africa) a large island. Picture two giant conveyor belts, facing each other but slowly moving in opposite directions as they transport newly formed oceanic crust away from the ridge crest
Earth Floor: Plate Tectonics
The theory states that Earth's outermost layer, the lithosphere, is broken into 7 large, rigid pieces called plates: the African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates. The plates are all moving in different directions and at different speeds (from 2 cm to 10 cm per year--about the speed at which your fingernails grow) in relationship to each other
The cycle basically starts over at this point with weathering and erosion processes breaking down and transporting the terrace sediment back into the river. As the sediment is deposited in the lake the main channel of the river will extend out into the lake, this lowers the gradient of the main channel which slows the flow of water through the channel and allows for the deposition of sediment in the channel
USGS FAQs - Earthquakes, Plate Tectonics, Earth Structure - Do earthquakes occur in Antarctica?
There is also a hint of a line of seismicity off the west coast of the Antarctic Peninsula and some activity in the Kerguelen Plateau (in the Indian Ocean "northeast" from the Pole). Some of our polar observers have told us they can hear the icequakes and see them on the South Pole seismograph station, but they are much too small to be seen on enough stations to obtain a location
Effects that are found at a divergent boundary between oceanic plates include: a submarine mountain range such as the Mid-Atlantic Ridge; volcanic activity in the form of fissure eruptions; shallow earthquake activity; creation of new seafloor and a widening ocean basin. (A frequent misconception is that the Ridge is a build-up of volcanic materials, however, the magma that fills the fissure does not flood extensively over the ocean floor and stack up to form a topographic high
Where Do Earthquakes Happen?
This time, the 'footwall' is on the 'downthrown' side of the fault, moving downwards, and the 'hanging wall' is on the 'upthrown' side of the fault, moving upwards
No comments:
Post a Comment