[amalia (OP)]

Derek got in touch with us to ask a question:
What is different between the Andes and the Himalayas that has caused the Andes to have lots of volcanoes and the Himalayas not to have any?
What do you think?

[alancalverd]

IIRC the Andes is essentially a volcanic range caused by the slippage of overlapping tectonic plates, but the Himalayas are "fold" mountains made by the crumpling of a single plate. But my last geography lesson was in 1962 and opinions may have changed! 

[Halc]

but the Himalayas are "fold" mountains made by the crumpling of a single plate. But my last geography lesson was in 1962 and opinions may have changed!

My understanding is that since India is the fastest moving plate in the world, the Himalayas are indeed a crumpling, but due to the collision of two plates.  I think the difference is that both are continental plates made of similar low density rock, and they just pile up rather than slip one over the other.  The Andes on the other hand is a subduction zone with a low density plate riding up and over the higher density ocean plate.

[Petrochemicals]

As a guess, the hymalayas are a lan on land collision zone, where as theandies are a land on sea collision zone. Altitude difference between the pacific sea bed and north india will be into the kilomerers, that is alot for the magma to break through, its easier for it to squirt out at the splitting area. The pacific sea bed is land that has been created by a spliting fault, whilst india was a landmass beforehand. You would have to look at crust thickness, some areas are far thicker than others.