How would you separate salt & sand, taking into account the fact that salt is soluble in water and sand is not?

The two can be mixed in water, since the salt is soluble it will dissolve and the sand will remain. To separate it from the water use filter paper and a beaker.

That result from subduction of oceanic plates beneath lighter continental plates. most of the earth's volcanoes are located around the pacific ring of fire because that the location of most of the earth's subduction zones.