Denali, in 2015 (Photo: Todd Paris/UAF/USGS)

This has been a big week for North America’s tallest mountain. First, President Obama changed its official name to Denali, the name that native Alaskans used for the mountain before the U.S. government decided in 1917 it should be called Mt. McKinley. And today, the mountain’s official height is being changed as well.

Denali shrunk, according to the U.S. Geological Survey.

Not by much, though! When the mountain’s elevation was measured in the 1950s, its height was determined to be 20,320 feet. Denali’s new official height? 20,310 feet—just 10 feet shorter.

Researchers trekking on the mountain (Photo: Rhett Foster/CompassData/USGS)

The new official height is actually a bit taller than the height measured in 2013, by a digital elevation model that used radar data. That method averaged the elevation of a wider area around the summit, and put the mountain at 20,237 feet, 83 feet below the 1950s number. 

In June of this year, four climbers went to the summit hauling GPS equipment to get the most accurate reading possible. They set their survey equipment directly on the summit. This method of measurement works by measuring the distance between the GPS receiver and satellites orbiting the planet. The climbers, one from the University of Alaska–Fairbanks and three from the company CompassData, returned in early July with a wealth of data. 

At the summit (Photo: Agustin Karriere, CompassData)

It took about a month, though, to determine the mountain’s official height: while satellites’ distance from Earth is measured with respect to the planet’s center, a mountain’s height is measured with respect to sea level, a complicated calculation. The GPS experts also had to take into account factors like the depth of the snowpack, USGS says. 

Given all that, an elevation change of 10 feet is pretty minor. The next tallest mountain on the continent is still hundreds of feet shorter than Denali. Plus, because of the tectonics beneath, Denali’s still growing, about 1 millimeter per year. Give it long enough and it could get that 10 feet back. 

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