Some historians think the European Dark Ages were called that because they were... dark.

Shorter growing season, dimly lit skies, colder weather. All caused by a confluence of volcanic activity that filled the skies with dust and ash that lowered the albedo of the earth, thereby cooling it.

Our concerns over global warming could turn in a second if the Pacific Rim, for example, began to pop a large number of eruptions... not to mention old favorites like Stromboli, Vesuvius, Etna, and others.

Man survives because he is in fact, highly adaptible. Many many life forms do too, but because man is (supposedly) intelligent and self aware, one of the things we do is "categorize" everything, including life. If we didn't differentiate between species then there would not be any extinctions... just life as it was "before" and life as it is "now" and life as it may be in the"future"