Everest is the highest mountain above sea level, but most of Mauna Kea in Hawaii is hidden beneath the Pacific, and measured from its base on the ocean floor to its summit it stands more than a kilometre taller than Everest, making it the tallest mountain on Earth.

Everest is the highest mountain above sea level, but most of Mauna Kea in Hawaii is hidden beneath the Pacific, and measured from its base on the ocean floor to its summit it stands more than a kilometre taller than Everest, making it the tallest mountain on Earth.

Mount Everest keeps the title most people mean when they talk about the highest mountain on Earth. Its summit is the highest point above mean sea level, at 8,848.86 metres, according to the height jointly announced by China and Nepal on 8 December 2020. That is not the only way to measure a mountain. On Hawaii’s Big Island, Mauna Kea rises 4,205 metres above the Pacific. From the surface, it is far lower than Everest. But the volcano does not be…