A(n) ________ is likely to host a waterfall or steep rapids today.

A ________ flood occurs when heavy rain strikes a mountainous area.

The ________ are a geologically old mountain range folded and deformed during the paleozoic.

Magma tends to rise toward earth's surface principally because ________.

A fiord is a ________.

Island arcs and andean type mountains are both examples of mountains formed by ________.

The principal characteristic that differentiates temperate and tropical rainforests is __________.

One limitation of wind power is that it ________.

Of the ~4,000 known minerals, the vast majority ________.

Of all the freshwater on the earth, approximately ________________ is trapped as ice.

Nonnative species disrupt ecosystems by _______.