And the title for tallest mountain goes to … either Mount Everest or Mauna Kea. The summit of Mount Everest is higher above sea level than the summit of any other mountain, extending some 29,029 feet (8,848 meters) high. However, when measured from its true base to summit, Mauna Kea takes the prize, measuring a length of about 56,000 feet (17,170 m), according to the USGS. Here are some of Mauna Kea's detailed measurements: The highest point is 13,680 ft (4,170 m) above sea level; the flanks of Mauna Loa continue another 16,400 ft (5,000 m) below sea level to the seafloor; and the volcano's central portion has depressed the seafloor another 26,000 ft (8,000 m) in the shape of an inverted cone.
Highest Altitude: An altitude of 8,850 meters (29,035 feet) above sea level makes Mount Everest the mountain on Earth with the highest altitude. "Highest altitude" means that it has the highest elevation above mean sea level.
Tallest Mountain: The base of Mauna Kea is about 6000 meters below sea level, and the summit is about 4000 meters above sea level. The distance between the foot of the mountain and the summit is about 10,000 meters. This makes Mauna Kea the "tallest" mountain in the world.
And here's one to really make it interesting:
Highest Above Earth's Center: The Earth does not have the shape of a perfect sphere. Instead, its diameter is greatest near the equator. In the diagram above, the gray dashed line is a perfect circle, and the solid blue line represents the shape of the earth (exaggerated a bit to make its departure from spherical obvious). Chimborazo is located near the equator where Earth's diameter is greatest. This makes the summit of Chimborazo the highest point above the center of the Earth.
Mount Wycheproof, the world's smallest registered mountain is located in Australia's Terrick Terrick Range, Mount Wycheproof stands 486 ft (148 meters to the rest of the world) above sea level, which is not bad as far as small mountains go.
In Texas they call that a mole hill.
You could hike to the summit of that one carl!