Sixty million years ago, when the Eurasian Plate collided with the Indian Plate, a chain of mountains was born. Since these plates were of similar density, neither could sink under the other. The rocks had nowhere to go but to climb.
Now, the Himalayas host the highest mountains on earth. Mount Everest It is the tallest, at 5.4 miles (8.8 kilometers) above sea level. After Mount Everest, the highest mountain is K2, which rises 5.3 miles (8.6 km) above the Earth’s surface.
Could these mountains be higher? For that matter, how tall can any mountain on Earth grow?
Theoretically, the mountain could be “slightly taller than Everest”, Jane Humphreys (Opens in a new tab)The University of Oregon geophysicist told Live Science. But first she will have to overcome some of the challenges that many mountains face as they grow up.
For example, because of Earth’s gravity, any pile of rock that grows into a mountain will begin to slacken, “much like bread dough will slowly flatten when placed on a table,” Humphreys said.
Related: Is Mount Everest really the highest mountain on earth?
Active processes, such as erosion, also help prevent mountains from growing too tall. Glaciers, vast masses of slowly moving ice, are particularly good at sculpting mountains.
Earth scientists refer to glacier erosion as “ice buzzsaws because they are so effective at turning away the sides of mountains,” Humphreys noted. “[Glacial erosion] It creates a very steep mountain which is then prone to landslides.”
The effects of erosion and gravity mean that “the larger the mountain, the greater the stresses from gravity, and the greater the tendency to collapse,” Humphreys said. And although Mount Everest “can conceivably rise higher, its steep southern side appears unstable,” which could lead to landslides.
However, there are ways a mountain can grow higher than Everest, Humphreys continued. It is likely to be up to 1 mile (1.6 km) high – but only if conditions are right. First, it must have been formed from volcanic processes rather than continental collision. Volcanic mountains, like the Hawaiian Islands, grow as they erupt. Lava flowing from volcanoes cools in layers, building volcanoes higher and higher. Finally, for a mountain to continue growing, it needs a continuous source of magma that is pumped higher and higher, allowing it to erupt, flow down the sides of the mountain, and cool.
This volcanic process is exactly how the highest mountain in the solar system, Olympus Mons, forms Mars. Olympus Mons is 16 miles (25 km) high, so high that it actually penetrates the top of the Red Planet’s atmosphere, Briony Horgan (Opens in a new tab)A planetary scientist at Purdue University in Indiana told Live Science.
Olympus Mons can get so tall because Mars lacks plate tectonics, the large clumps of crust that dominate Earth’s geological processes. Olympus Mons formed over a hotspot – a deep well of rising magma – that has erupted repeatedly. Just like the Hawaiian Islands, that erupted lava will flow down the sides of the mountain and cool in a new layer of rock.
However, even though the Hawaiian Islands also formed over a hotspot, the Pacific Plate keeps moving, so the islands wouldn’t stay over the hotspot long enough for their volcanoes to be the size of a mountain like Olympus Mons.
“On Mars, if you just have the same hot spot but the plate isn’t moving, you can form huge, massive volcanoes over hundreds of millions or billions of years of activity,” Horgan said.
But even giants like Olympus Mons have limits. According to Horgan, if the volcano is still active (so far, we haven’t observed any current activity), it is likely nearing the end of its growth. This is because the pressure required to keep pumping magma to the top of the mountain may soon not be able to overcome the forces working against it—the mountain’s height and Mars’ gravity.
“You can basically think of a volcano as a tube that you’re trying to pump lava through, and on some level, if it’s too big, too high, you don’t have enough force to get the lava in,” Horgan said. .
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