The One Minute Geographer: This Fragile Earth (9) And the Tallest Mountain is…?

Jim Fonseca
3 min readFeb 19, 2022
On the big island of Hawaii, Mauna Kea to the north stands about 125 feet higher in elevation than Mauna Loa, to the south. While there are many clouds in the photo, the white areas around the two peaks are snow caps. The red marks indicate recent lava flows. Photo from earthobservatory.nasa.gov

When I taught geography, I used to ask students the tallest mountain question and they would almost always know the ‘right’ answer. But then I’d say “No, the tallest mountain is on Mars. It’s called Olympus Mons and it’s twice as high as Mount Everest.”

Not a fair answer, but it helps makes the point that we measure mountain heights on earth from mean sea level and by that standard Mount Everest at 29,000 feet (5.5 miles) wins the contest. (I’m using heights rounded to 100s.)

But, if you go back to the first post in this series you may recall that the earth’s diameter varies a little bit because the earth is really an oblate ellipsoid, fatter at the Equator with middle age spread due to centrifugal force. Its radius is only about 25 miles wider at the Equator than at the poles, but that extra width makes a difference in the overall topography of the earth and in the height of its mountains.

Mount Chimborazo, Ecuador, from Wikipedia

It turns out that a geophysicist or an astronomer would not consider Everest to be the tallest mountain. They would pick Mount Chimborazo in Ecuador, near the Equator. Chimborazo at 20,500 feet (3.4 miles) loses out to Everest and many other Himalayan peaks in reference to sea level. It’s not even the highest mountain in the Andes — that would be Mount Aconcagua, Argentina, tallest mountain in the Western Hemisphere at 22,800 feet (4.3 miles).

Location of Mount Chimborazo, Ecuador, close to the earth’s bulge at the Equator. (Ecuador means Equator in Spanish.) Map from Britannica.com. Red dot and red line for the Equator added by the author.

But here’s why Chimborazo can hold up the foam ‘We’re number one finger:’ a geophysicist, measuring distance from the geometric or geodetic center of the earth would say Chimborazo is the farthest point away from the center, 6,800 feet (1.3 miles) farther away than Everest. And the astronomer would say “Think of it this way — Chimborazo is the closest point on earth to the moon.”

Now you may be asking — but if Chimborazo sticks out so much, isn’t it also that much higher than mean sea level? We’re touching on encyclopedia-length…

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Jim Fonseca

Geography professor (retired) writes The One Minute Geographer featuring This Fragile Earth. Top writer in Transportation and, in past months, Travel.