Mars mountains

Doug Wiens (
Wed, 14 Aug 1996 09:50:23 -0500

>> I'd like to ask a question of the geology braintrust. A while ago there
>> was a very informative post, perhaps by Mr. Morton, on why mountains on
>> Earth cannot be higher than some height (perhaps 6 miles?). But these
>> conditions can't apply to Mars, which has Olympus Mons at 8 miles high or
>> thereabouts. How come Mars can have higher mountains? Does it have
>> something to do with the red planet having a solid core?
> I believe it has to do with the mass of the planet, which affects the value
>for the gravitational acceleration on the planet's surface (little g). On
>Mars, we would weigh less on the surface than we do on earth. Similarly, a
>given volume of rock will weight less as well and you can pile up a higher
>pile before it collapses of its own weight. On earth, there's evidence of
>the Himalaya mountain chain spreading E-W laterally through normal faulting
>as they're being pushed up by the northward-directed collision of India with
> Also, on Mars, there appears to be no plate tectonic activity (except
>maybe very early in its history). That means that a section of the crust
>sitting over a mantle plume would stay there allowing a volcano like Olympus
>Mons to grow quite high. On earth, crustal plates move and you get chains
>of volcanoes like the Hawaiian Islands.

Mars also has a much lower thermal gradient. This results in a
thicker lithosphere which can support larger topography, and reduces
the thermally activated creep mechanisms that limit topography
in places like the Himalayas on earth. The lower thermal gradient
results from the smaller size of Mars, which allows internal
heat generated from radioactivity to escape easier.

Doug Wiens
Professor of Geophysics
Washington University, St. Louis