A continent-continent collision occurs when a continent or large island that has been moved along with subducting oceanic crust collides with another continent Figure The colliding continental material will not be subducted because it is too light i. There is tremendous deformation of the pre-existing continental rocks, and creation of mountains from that rock, from any sediments that had accumulated along the shores i.
Examples of continent-continent convergent boundaries are the collision of the India Plate with the Eurasian Plate, creating the Himalaya Mountains, and the collision of the African Plate with the Eurasian Plate, creating the series of ranges extending from the Alps in Europe to the Zagros Mountains in Iran. The Rocky Mountains in B. Transform boundaries exist where one plate slides past another without production or destruction of crustal material.
As explained above, most transform faults connect segments of mid-ocean ridges and are thus ocean-ocean plate boundaries Figure Some transform faults connect continental parts of plates. Transform faults do not just connect divergent boundaries. For example, the Queen Charlotte Fault connects the north end of the Juan de Fuca Ridge, starting at the north end of Vancouver Island, to the Aleutian subduction zone.
The boundary between the two plates is the Nootka Fault, which is the location of frequent small-to-medium earthquakes roughly up to magnitude 5 , as depicted by the red stars. Explain why the Nootka Fault is a transform fault, and show the relative sense of motion along the fault with two small arrows.
See Appendix 3 for Exercise As originally described by Wegener in , the present continents were once all part of a supercontinent, which he termed Pangea meaning all land.
More recent studies of continental matchups and the magnetic ages of ocean-floor rocks have enabled us to reconstruct the history of the break-up of Pangea. During the same period, the Atlantic Ocean began to open up between northern Africa and North America, and India broke away from Antarctica. To see the timing of these processes for yourself, go to time lapse of Continental Movements.
Within the past few million years, rifting has taken place in the Gulf of Aden and the Red Sea, and also within the Gulf of California. Over the next 50 million years, it is likely that there will be full development of the east African rift and creation of new ocean floor. Eventually Africa will split apart. There will also be continued northerly movement of Australia and Indonesia. The western part of California including Los Angeles and part of San Francisco will split away from the rest of North America, and eventually sail right by the west coast of Vancouver Island, en route to Alaska.
Because the oceanic crust formed by spreading on the mid-Atlantic ridge is not currently being subducted except in the Caribbean , the Atlantic Ocean is slowly getting bigger, and the Pacific Ocean is getting smaller. If this continues without changing for another couple hundred million years, we will be back to where we started, with one supercontinent. Pangea, which existed from about to Ma, was not the first supercontinent. A different explanation lies in different forces generated by the rotation of the Globe and tidal forces of the Sun and the Moon.
Listen here, Episode Plate Tectonics. Skip to content. Like this: Like Loading This animation shows, in a very exaggerated way, the sorts of movements Plate Tectonics implies. Plate Tectonics is a theory of motions at the Earth's surface, but to drive those motions, it relies on a planet with a very active inner life.
It is important to remember that the one-minute-long movie actually represents millions of years! In the Pacific Northwest, movement of three tectonic plates drive our earthquake hazard. The North American plate is moving to the west-southwest at about 2. This may seem like small and slow motion but over geologic time scales these movements add up to hundreds and thousands of kilometers, and can reform parts of the surface of Earth.
Vancouver Island to Cape Mendocino California and a large tract of seafloor real estate in between. But the central part of the old Farallon plate vanished beneath North America. The answer to this is no, the speed that N. America is moving away from the mid-Atlantic ridge matches, indeed controls, the rate at which new ocean lithosphere is generated at the ridge.
In the case of N. America, you need to think of the N. American plate, which comprises both continental and oceanic lithosphere, and stretches from the Mid-Atlantic ridge in the East right across the western Atlantic ocean, and the whole of the N. American continent to the complex set of plate boundaries along the western seaboard of N. America including the San Andreas fault. This whole section of oceanic and continental lithosphere is moving as a single unit — the N.
American Plate.
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