What is the tallest volcano in the world?

The tallest volcano in the world is located on the Argentina-Chile border, and is named Ojos del Salado. The volcano is 6887 meters, or 22,595 feet, tall.

Ojos del Salado has two summit peaks that are the same height. The volcano had a massive eruption over 1000 years ago, but has not had any confirmed eruptions since. It is considered active because of persistent fumarolic activity, and some people suggest that the volcano produced gas and ash emissions in 1993, although that hasn't been confirmed. The conditions around the volcano are very dry, although there is snow on the peaks during the winter.