# Mountains no higher that 15000 meters?

I just read a “Did you Know?” blog that stated: “due to the earth’s gravity, no mountain can be more that 15,000 meters high.” Is this true, and why?

• There are obviously many factors at play here. An obvious one is the higher mountains are the more rapidly they tend to erode. They get glaciers and things like that on their flanks that really scour them. Also normal faults tend to form and they slide downhill because of that. A big reason for that limit though is that mountains, because of the principle of isostasy, are required to have roots that displace an equal mass below the surface. When mountains get that high and roots go that deep the minerals at the bottoms of the roots undergo phase changes and you get the rock eclogite. Eclogite is denser than the mantle so it no longer provides buoyancy to the mountain on top, and it is thought that it probably drops off the bottom of the root and sinks into the mantle. Oh yeah, and 15000 meters is way to high, it is more like what Everest is just shy of 9000.

• For much the same reason that glaciers can only be 4800 meters thick. Granite will flow just like the ice will under enough pressure.

The weight of a cm^2 column of granite 15 km tall is 40 kN. While the bearing strength of granite is 20 kN/cm^2. A tower of granite could only be 7.5 km tall before crumbling, but due to lateral support — and I can’t remember the math, only the result — a mound can be double that. (Though intuitively I’d have wrongly guessed it could be three times that.)

Mountains the are coming out of the sea gain extra lateral support; id est, they float, and can get some what taller.

• 15000 Feet In Meters

RE:

Mountains no higher that 15000 meters?

I just read a “Did you Know?” blog that stated: “due to the earth’s gravity, no mountain can be more that 15,000 meters high.” Is this true, and why?

• Interesting question. If you were to plot the height of every point of land on Earth on a frequency graph, you would see that the vast majority of land is close to sea level, with a rapid decline in frequency as you go up in elevation to a single point maximum of 8848 meters ASL (Mt. Everest). The curve of that graph is related to the 15,000 meter maximum you refer to due to a combination of erosion and isostasy.

Essentially, the higher you go above sea level, the higher the rate of erosion. Erosion has the effect of bringing everything back to sea level, and the entire earth would be flat if it weren’t for the mountain building processes of continental collision and volcanism.

Of course erosion is partly controlled by gravity, but Mars has similar gravity to Earth with much higher mountains, up to 27,000 meters. Therefore the height limit can not be gravity alone.

In addition to the erosion, we have a phenomenen called isostasy. As the moutains build in height, the crust of the Earth is sufficiently “plastic” so that the mountain will “float” on the crust. The tendency will be for the mountains to reach gravitational equilibrium between the earth’s lithosphere and asthenosphere, which depends on their thickness and density of the crust, and the height and density of the mountains. The net effect will be the higher the mountain, the deeper the “root” of the mountain will reach into the crust..

I’m not aware of any mathematical proof of the 15,000 meter limit, but when you combine the effects of erosion and isostasy, it seems reasonable.

• Did they give any references or qualifications on that statement? I.e did it say ‘above sea level’ or anything like that? The reason I ask is the according to the USGS, Mauna Loa in Hawaii (the largest mountain on Earth as measured from its base to summit) is 17000 meters. Granted, a good portion of that is under water.

• apparently it is true.

I don’t see why though. Can’t find any explanation on google.

My guess, it would seem that it isn’t true. Can’t find any proof to back it up. Only websites with “weird facts” say anything about it. Also they don’t explain why, they just said “do to gravity”.

• i dont think that’s true,

bcuz mountain’s were formed due to the movements of tectonic plates.