Wait, what? While Mount Everest has the highest elevation *above sea level*, it is not the tallest mountain on Earth if you measure from the base to the peak. That title belongs to Mauna Kea, a dormant volcano in Hawaii. Mauna Kea rises 13,803 feet above sea level, but its base sits on the ocean floor. If measured from its true base at the bottom of the Pacific, it stands over 33,500 feet (10,210 meters) tall, making it significantly 'taller' than Everest's 29,032 feet. This tricky distinction arises from how we define 'height' versus 'elevation.' One measures distance from the ground it sits on, while the other measures distance from a global average of the ocean's surface.