From what I can tell, the Indian subcontinent slowly smashing into Asia is the first major collision of continental landmasses since the breakup of Pangaea.
Is that belief correct? And if so, does this mean that the Himalayas are the highest mountain range that has ever existed on our planet?
I’ll let someone else answer this more definitively, but at least let me correct your supposition that the current India-Asia mashup is the first of its kind. So untrue! To give just one example, Africa/Europe and the Americas have smashed into each other with at least as much force and duration not once but three times since the Precambrian*, each time (the event being called an “orogeny” – “mountain birth”) producing mountains about as high as today’s Himalayas, which were then eroded over tens of millions of years. Each orogeny took place along a different line, which is why we have the Appalachians/Sacandanavian range, but also the Taconic hills of eastern New York, etc.
As for how high the highest mountains have ever been on Earth, I don’t think we can know this exactly, but I seem to recall someone positing a theoretical practical limit for mountain heights, given the various processes involved, and I think it is indeed not much higher than 9,000 meters/30,000 feet.
(*old name for this era, I know)
Not likely, the Earth has some much larger, more ancient formations. For example, there’s the Massif Central, a large plateau in the south of France. It’s hardly impressive, nowadays, but it is simply the roots of a massive eroded volcano (as determined by the zircon minerals,) going far back into Earth’s history.
Mt. Everest is the highest mountain in the world above sea level but it isn’t the tallest mountain overall. Mauna Kea that forms part of the Big island of Hawaii is the tallest but it starts 13,800 feet below the water and is over 33,000 feet tall in total. I am just throwing that out there as a fun fact and one that shows mountains can be taller overall.
I’ve also seen the argument that the Andes are higher than the Himalayas, since the Himalayan mountains are sitting on a big friggin’ plateau that gives them a hefty head start, but the Andes just climb straight up from sea level.
“How the States Got Their Shapes” mentioned last week that the Adirondacks were much higher than the Himalayas. The are a few million years older as well.
Can you explain this? The Adirondacks were once 28,000 ft high or just higher than the Himalayas were before the Himalayas existed? Sounds pretty misleading.
In a small way, the Himalayas aren’t even the tallest they’ll ever be - Everest gets a little taller every year.
The claim is made in this “Geologic History of the Adirondacks”:
http://www.adirondack-park.net/history/geological.html
that doesn’t say where in the geologic time scale upstate New York has that kind of elevation, though. Perhaps while it was the interior of the Pangaean supercontinent?
I have been told by climbers that Mt. McKinley in Alaska is actually a higher climb than Mt. Everest, since Everest starts atop a big high plateau, while McKinley goes right up from the ground.
Lot of ambiguity in the last couple of cites.
“Upstate New York” means a lot of different things, geologically. As I explained above, the Taconic hills were approx. Himalaya-height mountains about 400-450 million years ago, after an America/Africa-Europe crunch episode. The Adirondacks are much older – more like 1 billion years old – and were not the result, AFAIK, of a crunch of continental plates, but rather mainly a granitic, etc. pluton which cooled underground, was uplifted, and the land around them eroded – a higher extension of the old stable craton of the Canadian shield. So, I doubt the Adirondacks were ever as high (above the sea level of the time) as either the Taconics or the Himalayas.
But perhaps the cite touting the height of the Adirondacks was referring to the fact that their “root” is (I think – easy to look this up) deep, deep underground. That is, as an above-sea-level expression of deep, old continental rock, they are in some sense “higher” than, say, the Taconics were (or the Himalayas are), because the Taconics and Himalayas were/are the product of continental edges colliding head-on (the Taconics were mainly an island arc, like Japan, which got crunched…but the idea is the same), rather than the uplift of a deeply rooted, relatively stable continental interior.
So, we have, in this thread, several definitions of “height”: 1. Relative to (contemporaneous) sea level (Everest is highest now); 2. Relative to a “nearby” seafloor (Mauna Kea is highest now); 3. Relative to a “nearby” dry-land plain (the Andes, and Denali/McKinley, have been mentioned); 4. Relative to the geologic base of the mountains themselves (that is, how far down do the same rock types, of the same age, go?) – perhaps the Adirondacks are especially high in this regard.
This cite from “adirondack park.net” seems not to refer to the height of the Adirondacks, but rather to their surface appearance. That is, it’s trying to inform us that a lot of what we see there – U-shaped valleys, lakes formed by moraines, bare-scraped-rock hilltops – is due to recent glaciation.
They mistakenly turned a “both-and” into an “either-or”. Obviously, what we see is a product both of big Precambrian geologic forces, and more superficial, recent glaciation.
I’ll also add that Pangaea wasn’t the first supercontinent, it was just the latest in a cycle of supercontinent formation and breakup.
IANA geologist or a scientist. But I do have vast store of useless knowledge gained from reading about all sorts of things.
Reaching back into that store of useless knowledge I seem to have read many year ago about a theory proposed by a geologist. Basically it was said that the height of the Himalayas is about the maximum that a body the size of the earth cans sustain. In other words, when the surface rises above a certain level, other factors will come into play that will not allow it to get much higher.
If the theory has any merit it could mean that there have been mountains higher than Everest but not by much.
So, take it for what it’s worth and flame me for my lack of cites and support. I’m just throwing something into the fray.
I have heard this theory too (another unsourced vague recollection). Essentially that the Earth’s mantle is too soft to maintain mountains above a certain height for too long without them sinking in to the mantle under their own weight.
The context was talking about how Olympus Mons on Mars is much taller only because Mars has a more solid interior for the mountain to sit on.
Thanks, that’s exactly the theory I was referring to.
Also, again from the vast store of useless knowledge, if the surface of the earth was reduced to the size of a cue ball it would be smoother than a well manufactured cue ball.
It seems to me that those factoids merge with each other. The makeup of the earth is such that its gravity forces it into a spherical shape. The makeup of the earth is apparently soft enough that it won’t allow itself to diverge far from a sphere. Makes sense to me but what do I know?
The much lower gravity on Mars would help a bunch too.
Another vote for non-expert recollection of unsourced factoids that Everest is near the bouyancy limit for a rock pile floating on our mantle.
But that’s for a more-or-less static condition. We could certainly imagine some sudden event like a meteor impact which could push up crater walls (i.e. mountain ridges) vastly higher than 30K ft. They’d subside quickly in geological time, but it might still be a million years before they slumped down to equilibrium height.
On a slower scale … If we posited that the Indian plate picked up speed and started going North at 2 or 3x the current rate, I’d expect Everest and the others to start gaining height much faster than they’re subsiding. Over a short geologic timescale that still might push it up to 35 or 40K (total WAG numbers).
As to why the plate motion would speed up, perhaps the arrangement of the mantle covective cells is shifting & the change finally arrived close enough to the surface to drive plate motion. Or the Eurasion plate starts to jam up against the others. etc. This is pure speculation on my part, but not obviously impossible on its face.
I read this too, something about the shape of the world not being a round sphere or something along those lines. So the bulge near the equator needs to be compensated for.
Aha, a fifth definition of “height”, to add to the four I collected above – “distance from the center of the Earth”. That’d make some Andean peak the winner.
You could add a 6th one: greatest displacement from the gravity well. Two points which are the same geometric distance from the center of the Earth could easily be at different levels in the gravity well due to the nonuniformity of the Earth’s interior.
Since we’re talking about crustal rock piles floating on a soft squishy gooey mantle, gravity differences might really be one of the better measures of “height”.
Something else not mentioned earlier: Differing sea levels over geologic time. Even if the quantity of liquid seawater & floating ice doesn’t change, the depth & distribution of seas certainly can. As could the total area of continents.
Lots of land-based ice could reduce the total sea water+sea ice, also changing the sea level. I doubt atmospheric humidity could change enough to affect sea level measurably.
IOW, just beacsue sea level today averages (made up number) 4001.54 miles from the geometric center of the earth, it need not have been that number since Day One.