"This divide runs from Cape Prince of Wales in western Alaska, through the Rocky Mountains of western Canada and the continental United States, then through the Sierra Madre Occidenal mountains in Mexico, through central America and along the Andes Mountains or South America"
The Earth's rocky outer crust solidified billions of
years ago, soon after the Earth formed. This crust is not a solid
shell; it is broken up into huge, thick plates that drift atop the soft,
underlying mantle.
The plates are made of rock and drift all over the globe; they move both
horizontally (sideways) and vertically (up and down). Over long
periods of time, the plates also change in size as their margins are
added to, crushed together, or pushed back into the Earth's mantle. These plates are from 50 to 250 miles (80 to 400 km) thick.
Answer:
1. Continental-continental convergence are both <em>continental crust</em> plates.
2. Buoyancy basically means these plates are light float on top of the Asthenosphere.
Explanation:
1. To go a little more into detail, this type of convergence ocurrs when two plates made of continental crust (not oceanic) collide. In the case of ocean-continent convergence, the denser oceanic crust sinks underneath the lighter continental crust.
In this scenario, we have two plates, neither of which want to sink, so instead of going down they just crumple and fold and keep colliding. This collision creates very high mountain ranges such as the Himalaya and usually doesn't contain any volcanic activity because no magma is capable of penetrating through so much crustal material.
2. As for why continental crust is buoyant and doesn't sink has much to do with its composition. Continental crust is made mostly of silicate material. This is very different from oceanic crust which is made of basaltic rocks and is therefore heavier. The term buoyancy refers to the 'floating action' of the continental crust on top of the uppermost mantle.
The answer is going to be d. hope that helped
