Manga causes powerful and explosive volcanic eruptions is

This should read "Magma (not manga)causes powerful and explosive volcanic eruptions and it is the molten rock which in the case of volcanoes flows out on the surface as lava or expels pyroclastic fragments. 

Sequoia national park  /  inyo national forest, california, u.s. mount whitney is the tallest mountain in california, as well as the highest summit in the contiguous united states and thesierra nevada—with an elevation of 14,505 feet (4,421 m).

None of them. they are likely to occur on any plate boundary