Mauna Kea is the tallest mountain on Earth when measured from its base to its peak.

Mauna Kea is a dormant shield volcano located on the Big Island of Hawaii that last erupted approximately 4,600 years ago. While Mount Everest reaches a higher altitude of 29,032 feet above sea level, Mauna Kea's total vertical rise is significantly greater. From its base on the Pacific Ocean floor to its peak, it measures approximately 10,210 meters or 33,500 feet. This surpasses Everest's height by more than 4,000 feet.The mountain's immense mass is a result of millions of years of volcanic activity over a tectonic hot spot. Geologists from the United States Geological Survey (USGS) note that the mountain is so heavy it has caused the oceanic lithosphere to sag. This creates a moat-like depression in the Earth's crust that extends several miles deep. This phenomenon is known as isostatic depression and is common among the largest volcanic structures on Earth.Because of its high elevation and isolation in the middle of the Pacific, Mauna Kea is home to the world's largest observatory for optical, infrared, and submillimeter astronomy. The Mauna Kea Observatories host 13 telescopes funded by 11 different countries. The atmosphere at the summit is extremely dry and stable, providing some of the best conditions on the planet for viewing the cosmos. This unique geography allows scientists to capture images with incredible clarity.