The ingredients for building mountains are pretty standard here on Earth: tectonic plates shift, the crust is pushed upward, and you have a mountain. But on Jupiter’s moon Io, things are done very differently.
Io has 400 active volcanoes that constantly layer sulfurous lava on the moon’s surface. Scattered around the surface are “bumps and lumps,” which are Io’s version of mountains, Phys.org explained.
The 100 or so mountains on this far-flung world are nothing like the mountains found on our planet, where ranges stretch across the horizon. On Io, they’re isolated peaks jutting from the surface seemingly out of nowhere in isolated blocks. And they’re massively high.
There have been many theories as to how these strange peaks form, but none have been proven. Thanks to some computer simulation, researchers from Washington University have determined that Io’s very high mountains are caused by its high level of volcanic activity, the Christian Science Monitor reported.
“People suspected the two were related,” lead author Michael T. Bland. “They hypothesized these mountains form by press faulting, basically blocks of Io’s crust uplifting… but it’s hard to demonstrate that.”
Dr. Bland and his co-author, professor William McKinnon, wanted to understand the mechanics of mountain building on Io, so they studied how the crust behaves and breaks due to volcanic stresses.
Here’s how mountains form on Io: Volcanic activity drives deep faults into the crust. Strain focuses on a single fault and rips through the rock to the surface. Magma from the moon’s interior moves up to the surface, and it’s then pushed downward to create further stress, deep in the crust. If there’s enough stress, parts of the crust jut upward, forming a cliff or isolated mountains.
“The mountains reduces these stresses and allows the magma to more easily be transported from the crust,” Bland said. “That’s the big result.”
Interestingly, the researchers also discovered that the building of mountains is how Io cools itself. On Earth, tectonic plates are the top layer in a convection system that, in tandem with volcanic eruptions, keeps the Earth cool.
On Io, magma pushes to the surface, cools, and is then sucked back down into the warm interior. But the deep stresses this creates limits the magma’s path to the surface. When mountains form, they ease this stress and let the magma flow — and this is how Io cools itself.
This interaction may explain why eruptions often occur near mountains on Io. The forces beneath the crust are “incredibly high,” McKinnon explained. The forces are released when they reach the surface: an eruption of magma.
“Heating at depth causes the rocks to want to expand, and since there’s no room to expand, you again get compressive forces,” he said.
The relationship between volcanoes and mountains on Io is peculiar, though, because if a volcano is erupting and taking away the heat and thermal stresses, mountains don’t need to form. If they stop erupting, the crust heats up, gets stressed, and mountains are built to cool everything down.
It’s possible that this unusual process is happening on the surface of other planets, but Bland said if he hadn’t seen it on Io, he wouldn’t have believed it possible. McKinnon agreed that the process is one-of-a-kind but could’ve happened on Earth long ago.
“It’s a novel mountain-forming mechanism that we don’t see elsewhere in the solar system. But the same kind of thing could have happened on Earth, when it was very young and entirely covered by a shallow ocean. Because there was still lots of volcanism, mountains like those on Io might have burst through the ocean. They might have been the first emergent land on Earth.”
[Photo by NASA/Getty Images]