Strombolian eruptions are characterized by convecting eruption clouds of volcanic ash or tephra. Hawaiian eruptions are characterized by continuous fire-fountaining. Mount St. Helens will never erupt again because the magma is all used up. Ophiolites are fragments of ancient oceanic crust that have been thrust up onto land. Volcanoes above subduction zones commonly erupt quietly, as effusive eruptions form viscous lava flows and ash flows.
Continents form by accretion at convergent plate boundaries, taking place over billions of years.
The Moon is about one-fourth the diameter of Earth but is much more dense. Sinuous rilles show that the Moon once had a hydrosphere but that it is now gone. Lunar volcanic eruptions are very ancient and occurred mostly in the period between one and two billion years ago. Mercury is only about one-third the diameter of the Earth but is very close to the Earth in density. Answer on these sheets below.