The Mauna Kea volcano is actually taller than Mount Everest, if you count the piece of the volcano that is underwater! Mauna Kea is an inactive volcano on the big island of Hawaii. It is about a million years old, created when the Pacific tectonic plate moved over the Hawaiian hotspot, which is a chamber of liquid magma from deep inside Earth. It last erupted about 4,600 years ago. Mount Everest stands 29,035 feet above sea level. Mauna Kea only stands 13,796 feet above sea level, but the mountain extends about 19,700 feet below the Pacific Ocean. Over half of it is submerged! That means that the total height of Mauna Kea at about 33,500 feet, which is about a mile taller than Mount Everest!