New answers tagged plate-tectonics
2
You didn't dive deep enough. You're asking about an area on a high-level, generalized map of basement rock provinces.
There were several orogenies at the southern boundary of the Wyoming craton. Between 1800 Ma and 1000 Ma, a series of island arcs accreted to southern Laurentia, building up the pink area on your map.
The earliest of these was the Yavapai ...
2
The interpretation of most of these interfaces is uncertain. Most of these plate boundaries are ancient, poorly exposed, have been metamophosed in later orogenies, and have suffered significant amounts of later erosion making it very difficult to say too much about the earlier character of the contact. Theoretically, you could have a transform fault that ...
-1
The simplified answer is that most volcanoes occur where the crust is thin. This allows magma from the Earth's upper mantle to rise and create trouble. Most active volcanos are found at the bottom of the sea where plates are spreading! We just had one erupt near Tonga. Many island chains are made from volcanic activity. Plates that collide make ...
13
Or is the continental crust too dry?
Exactly this. Continental collision zones are actually full of volcanic rocks, which formed at the time before it was a continental collision zone. The Wikipedia article on the Geology of the Himalaya has a nice summary of the suture zone:
"Dras Volcanics": are relicts of a "Late Cretaceous" to "...
5
Two major reasons, crustal thickening and thermochemical interactions.
Heat plumes, whether from crustal recycling or the deep mantle, can only melt through so much rock before they lose heat and either convect away or freeze on/in to the rock they have penetrated as intrusive deposits. Crustal thickening as rock piles up at convergent margins means that ...
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