Dont get me wrong, I have no doubt that the big E is the tallest, but lately the heighth has been reported at 29,035 feet. 7 feet higher than previously reported. Why? Because it’s most likely rising, as are the other Himalayan giants, (dont jump down my throat - not 7 feet in fifty or even a hundred and fifty years) and because the methods used to measure height have improved. But heres the thing I dont understand - how do you determine sea level in the middle of Nepal or Tibet? The very mass of these mountains would create some extra gravity, and so the level of the “sea” would rise. Do you take that into account when calculating? Or do you just go step by step (Figure out Darjeeling, and from there figure out Katmandu, and so on and so on)?
Thank you for your question, df, but it’s a good idea to post a link to the Mailbag article in question, espescially if it’s an old one (no longer onthe front page). The link for this one is Which is taller, Mt. Everest or K2?
[Edited by Chronos on 10-07-2000 at 04:11 PM]
What he said.
Actually, to answer the OP, the extra mass of the mountains on top is compensated for by a deficit of mass below. This is called isostasy, and is a lot like an ice cube floating in water–if you were to melt the mass of the ice cube, the water level would not change at all.
'Course, that is not an exact compensation, or the mountains would not be rising–but all the geodesists do is fit an ellipsoid to the data anyway, and call that sea level.
Varying snowpack on Everest can vary the height of the mountain too, though some say the extra 29-37 ft. were added because otherwise everyone would think the measured height of Exactly 29,000 feet was a round off.
- Jill
Uhm, Jill, according to the National Geographic, they measure the height of the solid rock beneath the snow for that very reason. Last year, NG co-sponsored an expedition to measure Everest’s height more accurately than ever before. Besides using GPS equipment to pinpoint both the summit’s height and location, they also used snow-penetrating radar to determine how much snow was on the summit at the time it was measured.
29,035 feet is the height without snow. It is getting taller* and the entire mountain is moving northeastward at 3 to 6 milimeters per year.
More info can be found here and here.
*The difference in height does NOT mean the mountain has grown seven feet since it was last measured in 1954. It means that previous measurements were less accurate.
I read once (I believe it was in Colin Tudge’s book The Time Before History, but I wouldn’t swear to it) that the Himalayas aren’t getting any taller, because the rate at which they’re still rising is matched by erosion. Is there any way to know if this is true?
Well, of course it’s getting taller.
It eats lots of vegetables and protein (mostly in the way of would-be climbers, admittedly), and it’s a young mountain, still has a long way to grow before it reaches maturity. Its parents are probably grumbling about how rapidly li’l Everest outgrows its clothes, every few hundred years or so.
But isn’t Mt. Everest’s and K2’s base is some 10,000 feet above sea level? What about measuring a mountain from its base? Wouln’t Mauna Loa, whose base is some 42,000 feet below the surface in the Pacific Ocean, be actally the tallest then, at 56,000 from its base? Is this ‘measuring the tallest mountain’ like measuring who is taller between Kareem Abdul-Jabbar wading in the three-foot section of a swimming pool, and Gary Coleman sitting on a 3-foot high lifeguard’s chair?
I have fixed the link (I hope) – CKDextHavn
[Edited by CKDextHavn on 11-03-2000 at 06:59 AM]
capacitor:
Sure, a little. But you have to define “tallest” somehow. Maybe measuring “average height above surrounding terrain” would be a more fair standard, but then you’d have the question of how far to go for the surrounding terrain. A ten-mile radius? A thousand miles? Any decision you made about that would be arbitrary…less arbitrary, I daresay, and less consistent than “average height above sea level.”
But I think you’re correct that, when measured from the average level of the ocean floor, Mauna Loa is taller than Everest, and is the tallest mountain on Earth.
capacitor, your link to Mauna Loa doesn’t work.
Are you measuring Everest from the average level of the ocean floor too?
Instead of Gary Coleman on a high chair, I think we should put Shaquille O’Neal in three feet of concrete.
How is it that a rinky-dink planet like Mars gets such a MF of mountain like Olympus Mons? Beats the hell out of anything we have to offer, and it ain’t even close.
The real question isn’t which one’s taller, but which one’s more difficult to climb. Everest isn’t a cakewalk, but K2 is a lot harder to get up.
hijack, part 3
Denali basically sits at sea-level, and, using the criteria of “actual” height, is taller than Everest.
Yargh, THWACK!
Mating call of the ice-climber)
The force of gravity does limit how big a mountain can get. If a mountain was too big, it would crush under its own weight; the strength of the rock has to be enough to withstand the force of the gravity. Mars has less gravity, so it can have taller mountains.
I’m not positive of this, but I’ve heard that Everest is pretty near the upper limit of mountain sizes on Earth, while Olympus Mons is also near the limit on Mars.
Also, just to add to the confusion of what convention to use when measuring mountain height, I think Chimborazo, in Ecuador, is the tallest mountain on Earth as measured from the center of the earth (because of the equatorial bulge).
Let’s try that Mauna Loa link again:
Sorry, but can’t hotlink it. For some reason, when one uses url code, it adds “http://boards.straightdope.com/sdmb/” to the linked site.
http://hvo.wr.usgs.gov/maunaloa/
You have to put “http://” in front of it. And you do not have to use url tags, either.
Olympus Mons is not only a huge mountain, it is a huge volcano too.
IIRC there are another 4 or 5 huge volcanoes on Mars too but nothing like the size of OM.
They are so high that they breach the thin almosphere and when dust storm occur are the only surface points visible to earth.
The sheer size of them has something to do with the Martian lack of plate tectonic movements which have ceased motion since the interior of Mars is believed to have cooled.
I’m not too sure of this but, OM is not a tectonic edge volcano but is of the same type as Hawaii, a basaltic flow type.It grew from an upward convection flow of material from the earths interior which breached the crust.It does not sit on a tectonic fault line such as the ‘ring of fire’ around the Pacific rim.
On Hawaii the crust rotates with respect to the earths interior so that a series of islands have been formed but on Mars it is thought that this rotation did not happen since it was not hot enough, thus OM was formed over the blowhole and just grew and grew.
casdave is largely correct about Olympus Mons. It is 27 kilometers tall, and is a “shield” volcano like Mauna Loa and the mountains of the Pacific Northwest.
The three other major volcanos, Pavonis Mons, Arsia Mons and Ascraeus Mons, are all also 27 kilometers tall, but they are much less massive than Olympus Mons. Olympus Mons covers an area roughly equivalent to the entire state of Arizona.
Even the caldera opening at the top is forty miles across.
Isn’t Mt. St. Elias, in Alaska, the tallest, since it is a coastal mountain that rises straight out of a deep oceanic rift?