Mauna Kea is the highest mountain in the world when measured from its base on the ocean floor.
This dormant volcano rises about 4,205 metres above sea level, but its base lies on the Pacific Ocean floor. Measured from that underwater foundation to its summit, Mauna Kea stands more than 10,000 metres tall, exceeding Mount Everest’s height above sea level.
Mount Everest remains Earth’s highest mountain above sea level, while Mauna Kea is often described as the tallest mountain from base to summit. Mauna Kea is on Hawaiʻi Island and has become an important astronomical observatory site because its summit is high, dry, and above much of the atmosphere.