Answer:
The magma that melts in the upper mantle and erupts at the mid-ocean ridge has a different composition (higher in Ca, Mg, Fe and relatively lower in Si and Al) than the composition of the magma (more Si, Al, Na, K rich in relative terms) that built the continents. Melting different degrees (2%, 5%, 30%) of a rock with a mantle-like composition generates magma of different Al, Si contents. Continents grow at their edges by partial melting of oceanic crust that is being subducted, generating magmas of a somewhat more Si, Al-rich composition than the subducting slab itself. The chemistry and physics of melting a mixture of minerals rather than one homogeneous substance has the wonderful outcome of creating two distinct types of crust:
Answer:
12 years is the answer good luck sit
Answer:
it made easier for crazy Americans to tour
Explanation:
tell them to bring my all my garden gnomes and cheeses its I can still hear there voices at night
Answer:
The Co-ordinate of the <u>midpoint of RT = 33</u>
