# Highest Mountain

1. Jul 30, 2008

### Mk

Mount Everest is the highest mountain according to sea level, but can we know if there has ever been a higher mountain in geological history?

2. Jul 30, 2008

### Andre

How would you do that? Interesting possibility is the O2 isotope composition in limestone. Since the rayleigh effect strongly depletes heavy isotopes 18O and 2H in precipitation at higher elevations, it may be registered in weathering of silicate rocks to limestone. But then again the dew point temperature is also strongly determining the isotope ratios (d18O and dD), so we have -as just about always- one equation with more than one variables.

3. Jul 30, 2008

### mgb_phys

You can also work out the maximum possible height of a mountain from rock strength.
It's around $h = 16 \gamma / \rho g$ where $\gamma$ is young's modulus and $\rho$ is density
which gives roughly the same height as Everest.

4. Jul 30, 2008

### LURCH

I don't think this really works, because a wider mountain could be taller. Also because Everst is only the tallest according to sea level, and another mountain with its base higher above sea-level would be higher if it were as tall as Everest.

However, you could simply check to see if Everest is currently being thrust up. If it isn't, then it's being worn down, so there was a mountain higher than Everest; Everest!

5. Jul 30, 2008

### mgb_phys

Only if it was a specific and unlikely shape (exponential curve - so mass above a certain level is less than the mass below)

Yes Mauna Kea is slightly higher from it's base (underwater) - but it's only an estimate, the factor depends on the shape of the mountain. It can also behigher if there is somthing to stop the base spreading out.

Generally the himalayas are in isostatic equilibrium, Everest is being worn down by erosion but the reduced weight means it floats up and maintains roughly the same height.

6. Jul 30, 2008

### Count Iblis

According the the NGC series "Earth Investigated" there were mountains higher than Mount Everest, I think in http://en.wikipedia.org/wiki/Arctica" [Broken], I don't remember...

Last edited by a moderator: May 3, 2017
7. Aug 18, 2008

### Mk

What values did you use to find roughly the same height as Everest?

8. Aug 18, 2008