Question:
Questions On Plate Tectonics?
anonymous
2010-05-17 10:31:59 UTC
1. Name the 3 types of boundaries between lithospheric plates?
2. How can ocean basins change in size?
3. Convergent plate boundaries can be in 3 different settings. What are they?
4. What happens when 2 continents collide along a convergent plate boundary?
Three answers:
anonymous
2010-05-17 12:15:36 UTC
(1) Boundaries



* Divergent, where plates move apart, such as at the Mid-Atlantic Ridge spreading apart North American and Eurasia



* Convergent, where plates come together, such as at the Peru-Chile Trench, where the Nazca and South American plates collide, or Indo-Australia meets Eurasia



* Transform, where plates move past each other with no creation or destruction of crust, such as the San Andreas Fault Zone separating the Pacific and North American plates.



(2) Ocean basins



Basins change in size as tectonics moves plates -- either a spreading center opens them (the Atlantic), or on the other end of the plate, converging boundaries close them (the Pacific).



(3) Convergent boundaries depend on type of crust, essentially only two types, but with one technicality



* Continental-continental -- Two pieces of continental crust slam together. Neither piece is dense enough to subduct, so it's like a collision between buses. Rock in the middle gets squirted up and out, with enormous amounts of dangerous seismicity. This is how the Himalays were created, as the Indo-Australian plate is hitting the Eurasian plate. In the case of continental-continental, the mountain range will be non-volcanic.



* Oceanic-continental -- A piece of oceanic crust and a piece of continental crust slam into each other. The oceanic crust will *always* be cooler and denser, and will subduct beneath the continental crust, meaning that it dives into the mantle. This creates a deep sea trench. As the descending plate gets deeper, it reaches a point at which it melts along a full plane, creating a long line of new, hot magma. These magma chambers and plums rise through the mantle and eventually out through the surface of the continental crust, creating a lava flow. Over hundreds or thousands of subsequent lava flows, you'll end up with a genuine volcano, and as this is happening on a whole plane, you get a full-blown volcanic mountain range. These are usually viscous, felsic flows of thick lava that form stratovolcanoes. This is what has created the Andes (Nazca subducting beneath South America) and the Cascades (Juan de Fuca subducting beneath North America). These boundaries have large, deep earthquakes, but not frequently.



* Oceanic-oceanic -- Almost identical to oceanic-continental, except that the plates have to decide for themselves who is denser and who is lighter. Whichever one is denser will subduct. Everything else is the same, except that the lava is obviously erupted at the bottom of the ocean. But given time and many lava flows, a line of volcanoes will pop out of the surface as dry volcanic islands, called a volcanic island arc. This is how the Aleutian Islands were created (Pacific plate subducting beneath North American plate), and the Japanese Home Islands (also the Pacific plate beneath the North American plate, didn't know that, did you -- they're just very active, so have merged into larger islands) and the Marianas Islands (Pacific beneath Philippine plate).



* Note that the Hawaiian Islands were NOT created through convergence. They're hot spot volcanism, which is completely different.



(4) Um, see #3 above. Transform boundaries are *not* collisions.
anonymous
2016-04-14 09:05:01 UTC
First of all, when the waters redrew after the flood the whole topology changed. Second, if there was a continental drift it was much faster do to a more active volcano activity at the time of the flood. It is unnatural to believe that the continental drift and other things are constant when they depend on things like volcano activity, solar flares and many others. They start with the absolutely false assumption that things in nature change on a constant rate when they never do.
Madeira Holidays
2016-02-16 08:41:35 UTC
https://www.platecreator.com


This content was originally posted on Y! Answers, a Q&A website that shut down in 2021.
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