Oddball Geological Features: Part 4 - Olympus Mons on Mars

As I’m sure many of you already know, geology is the study of the earth’s physical structure and the processes that make it tick. What we learn from our own planet, theoretically should apply to other terrestrial planets as well. In the case of Mars, our knowledge of the red planet is limited to satellite imagery and the data we’ve collected from the four rovers we've successfully landed on the planet. While much can be gathered from this data, without actual people and scientific instruments on the planets surface, it's difficult to be ascertain what is happening on Mars geologically. However, there is one behemoth piece of evidence that Mars, had or has, similar geological processes as Earth– the massive shield volcano Olympus Mons.

This is a topographical mapping of Olympus Mons on Mars. Note that the topography around the volcano is relatively low. [Image Source]

This gargantuan and potentially active volcano has no rival in the entire solar system. From base to summit, it stands at 88,600 ft (16 mi or 25 km) and has a diameter of 374 mi (624 km). To help put this in perspective, Olympus Mons is nearly 3 times taller than Mt. Everest (29,029 ft) and is approximately the size of Arizona! If you were standing at the summit, the relief (slope) of the mountain is so vast, the base would go beyond the horizon– meaning the volcano is so big it literally curves with the surface of the planet.

Did I mention that it’s practically sticking out of the Martian atmosphere?

The atmosphere on Mars is very thin to begin with, but at the the summit of Olympus Mons, it’s only 8% (0.047% Earth equivalence) of the normal atmospheric pressure of the planet. Put this monster on Earth and from sea level it would still stand at 66,897 ft. That’s nearly twice the height normal jets fly and it would be 4.6% Earth’s atmospheric pressure at the summit. Even on the summit of Mt. Everest, which is about a third (33%) of the Earth’s pressure at sea level, oxygen canisters are highly recommended to make it to the top. Basically, you would need a space suit to reach the peak of Olympus Mons.

Olympus Mons towers over Earth's biggest mountains.[Image Source]

While I could be here all day dishing out amazing facts about Olympus Mons, I sort of have to get down to the actual geology of it all, because you know, that’s what I do.

So how did Olympus Mons form? Well, there are a few different factors at play here. As I mentioned earlier, the Martian volcano is in fact a massive shield volcano. Here on Earth, a great example of a shield volcano is Mauna Kea in Hawaii, which is home to the Mauna Kea Observatories. While Olympus Mons isn’t the only volcano on Mars (see Tharsis Montes), it’s ability to stand out from the crowd leads geologists to believe that Mars, unlike Earth, lacks mobile tectonic plates.

[Image Source]

As a result, this would make Olympus Mons a stationary hotspot, allowing the volcano to discharge lava until it reached the extraordinary height we see it at today. Here on Earth, we have hotspots as well (e.g. Hawaii, Yellowstone), but due to constant plate movement from mantle convection, our planet has the ability to release energy more efficiently. It should also be noted, due to the smaller mass of Mars, gravity on the planet is 0.376 (38%) of the Earth standard– so someone that weights a 100 Ib on Earth would weigh 38 Ib on Mars. In turn, the magma erupting out of Olympus Mons had lower gravitational forces applied to it. This meant there were much larger lava flows, which played a significant role in the size of the volcano as well.

All being said, that’s not to say Mars didn’t have active plate tectonics at one point in its history, but if it did occur, it most likely happened when the planet was in its youth. Geological features such as Valles Marineris (known as the Grand Canyon of Mars) appears to be a strike-slip fault zone, which is very similar to the Dead Sea fault zone on Earth. Though there are other hypotheses regarding the Valles Marineris origin, this explanation would appear to be the most accepted in the astrogeological community.

I hope that one day I’ll get to see a colony of some sort on Mars. I guarantee there will be a geologist, amongst many other scientists on that exploration. It’s examples such as Olympus Mons that led me down the path of geology– well, volcanoes and mountains in general. If you haven’t read the first three posts of this series, be sure to check them by clicking on the links below!

Part 1 – The Chocolate Hills of Bohol

Part 2 – The Sailing Stones of the Playa

Part 3 – The Rainbow Mountains of China

Bibliography:

https://en.wikipedia.org/wiki/Olympus_Mons#Geology
https://en.wikipedia.org/wiki/Tharsis_Montes
https://en.wikipedia.org/wiki/Planetary_geology
https://en.wikipedia.org/wiki/Geology_of_Mars#Volcanism
https://en.wikipedia.org/wiki/Tectonics_of_Mars
https://en.wikipedia.org/wiki/Fault
https://blogs.agu.org/martianchronicles/2009/05/23/olympus-mons-is-how-tall/
https://en.wikipedia.org/wiki/Valles_Marineris#Formation
https://en.wikipedia.org/wiki/Shield_volcano
https://blogs.agu.org/martianchronicles/2008/09/24/low-gravity-volcanoes/