How tall is the biggest volcano and where is it?

Answer 1

Depends on what you mean by "big." The volcano with the tallest overall height, from base to summit, is Hawaii's Mauna Kea. However, two thirds of that volcano's height is underwater, since it rises from the sea floor. The volcano with the highest summit above sea level is Chile's Ojos del Salado in the Andes Mountains. The volcano with the highest point above earth's center is Chimborazo in Ecuador (due to earth's very slight equatorial oblateness due to orbital centrifugal force.)

It is noteworthy to mention, however, that the Olympus Mons volcano on Mars is much larger and taller than any of earth's volcanoes.