The heat from the Mt. St. Helens eruption melted snow and ice causing mud flows which greatly enlarged streams and rivers flowing down the mountain.

A fissure (a narrow opening) eruption typically occurs where there are diverging plates such as along the mid-Atlantic Ridge where a "window" is opened to the mantle below the crust.

A tsunami is a wave generated by an underwater earthquake.

Isostatic adjustment is a rising up the earth's crust after being depressed such as by glaciers or when erosion removes sufficient mass from a mountain chain. This adjustment is an attempt to reestablish a previous equilibrium.