Mars hides a volcano two and a half times taller than Everest and roughly the size of Italy. Its slopes are so gentle you might not notice you were climbing the tallest mountain around.
3 min read · 8 key facts · 7 terms decoded
A Mountain the Size of a Country
Olympus Mons is a gigantic shield volcano on Mars, standing about 21.287 kilometers high — roughly 2.5 times the height of Mount Everest above sea level. It is the tallest volcano on Mars and is roughly tied with Rheasilvia on Vesta as the tallest mountain in the Solar System.
It is breathtakingly wide too, spanning about 600 kilometers and covering some 300,000 square kilometers — about the size of Italy or the Philippines.
Gentle Giant
Despite its height, Olympus Mons isn't a steep cone. The average slope on its flanks is only about 5 percent, because runny basalt lava spread far and wide — the signature of a shield volcano.
Its outer edge, though, drops off sharply in an escarpment up to 8 kilometers tall. The whole enormous pile is supported by a 70-kilometer-thick lithosphere.
The Collapsed Summit
At the top sit six nested calderas — collapse pits formed when underground magma drained away. Together they make an irregular depression about 60 by 80 kilometers across and up to 3.2 kilometers deep.
These calderas range in age from about 350 to 150 million years old, and one study placed a magma chamber roughly 32 kilometers below the caldera floor.
Still Young in Places
Olympus Mons sits on the Tharsis Rise, an ancient vast volcanic plateau. It last erupted around 25 million years ago — recent in geological terms.
Some lava flows on its northwestern flank are as young as 2 million years old, hinting the volcano may not be entirely dead. The air at its summit is thin: about 72 pascals, only 12% of the average Martian surface pressure.
Key terms, decoded
basalt
A dark, fine-grained volcanic rock formed from low-viscosity lava.
calderas
Large collapse craters formed when a magma chamber empties beneath a volcano.
escarpment
A long, steep cliff or slope marking a sharp change in elevation.
lithosphere
The rigid outer rocky shell of a planet that supports surface features.
Olympus Mons
The tallest volcano on Mars and one of the tallest mountains in the Solar System.
shield volcano
A broad, gently sloping volcano built from runny lava flows.
Tharsis Rise
A vast ancient volcanic plateau on Mars where Olympus Mons sits.
This Quicky is an original summary based on the Wikipedia article “Olympus Mons”, available under the CC BY-SA 4.0 license.
