What's the tallest mountain in the world?

Answer 1

The answer depends a little bit on how you define "tallest" and "mountain".

The highest elevation above mean sea level is Mt. Everest (Chomolungma), at 29,029 feet or 8848 m.

However, Everest sits on top of an already high base. Reasonable figures for the "base" of Everest range from about 4200 m on the south to 5200 meters to the north, meaning Everest itself only accounts for about half, or slightly less, of the overall height.

In contrast, Mt. McKinley (Denali) in Alaska is only 20,327 feet (6194 m) above mean sea level, but its base is a sloping plain with elevations between 300 and 900 m. If Mt. McKinley sat on a base as high as that of Everest, it would be at least 3000 feet higher than Everest.

Also, there's Mauna Kea in Hawaii. It rises to only 13,796 feet (4205 m) above sea level, but its base is the ocean floor, meaning its height above base is over 10 km, nearly a mile taller than Everest even if you count Everest's base as part of its height.