# Geology (what do you think?)?

How does the point at which melting occurs control the distance of the volcanic arc from the trench?

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• Anonymous
2 months ago

The higher the melting point, the farther from the trench melting can occur.

Come on, this is simple common sense.

• 2 months ago

The idea is that the descending plate is contributing to that melting, and given that temperature increases with depth, and that plates descend at an angle, the depth of "melting" will occur at some distance from the region where the plate starts descending.  Simple geometry, basic right triangle. We know angle of descent of the hypotenuse, and we know the approximate length of the perpendicular (depth), so we can figure out the length of the side that represents distance from subduction.

The melting process is a lot more complicated than I paint it to be, but the general idea is still true.  A certain range of depths is required to achieve melting temperatures.  Magmas rise up more or less directly (volcanoes appear above the melting that happens at depth).

A real factor is the release of water from the wet slabs of descending oceanic crust.  The temperature issue is still the main thing though.  Can't melt if  isn't hot enough to melt.  How to get hot enough? go deeper.

• Kenny
Lv 7
2 months ago

The less viscous the magma the higher the speed it may reach before being expelled . At a higher speed the inertia will carry it further making the arch at a higher angle .  If I understand your question .

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