Our Mountains Won't Get Any Taller, and Here's Why

Earth's mountains can only reach so high. There is a stunning consistency with the world's tallest mountains, with most hovering right between 27,000 and 28,000 feet high. Only our tallest mountain, Mount Everest, pushes that boundary, daring to be more than 29,000 feet high. Amazingly, Mars' Olympus Mons, the tallest mountain in our solar system, stretches three times that height. So why can't Earth's mountains grow as tall? New research argues that our planet's glaciers just won't let them.

According to a study recently published in the journal Geology, Earth is so abundant with water that glacial formation around a mountain is inevitable, especially during an ice age.

When glaciers form on a mountain, they carve amphitheatre-shaped hollows into them called cirques. It's these hollows that eventually limit how high a mountain can grow before collapsing upon itself, regardless of what kind of volcanic or plate tectonic activity helped facilitate its formation in the first place.

To determine this, Sara Gran Mitchell, a geologist at College of the Holy Cross in Massachusetts, and Elisabeth Humphries at the University of North Carolina at Chapel Hill, measured the elevation of 14,000 cirques (long freed of their icy beginnings) around the world.

The pair discovered that mountain summits rarely rose more than 2,000 feet (about a third of a mile) above the highest cirque.

Interestingly, there also appeared to be a strong correlation between cirque height and climate, in which both the highest cirques and peaks were consistently taller near the equator and lower at high latitudes where it's cooler.

So how exactly does this work? According to the study, a cirque is kind of like a glacier's means of fighting dirty, going for the "knees" of a mountain, and weakening just how tall it can stand before falling over. More specifically, glaciers carve out the floors and walls of a cirque over time, steepening slopes and making them more vulnerable to time and erosion - the inevitable doom of even the tallest of mountains.

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