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It also helps that the Himalayas have slowly grown from nothing over the past 50 million years. The ancestors of the bar-headed goose had the opportunity to gra

It also helps that the Himalayas have slowly grown from nothing over the past 50 million years. The ancestors of the bar-headed goose had the opportunity to gradually adapt as the mountains rose. (Not all birds can do this, even with their superior lungs.) edit: I had assumed that the Himalayas grew gradually over 50 million years, but it turns out that the current growth rate is way too fast for that. It would take less than a million years to reach the current height. There must have been regular apocalyptic landslides in the geological history of the Himalayas to limit the height of the mountains?

mncharity 6y ago
> limit the height of the mountains Gravitational potential energy becomes sufficient to pay for rock deformation. As with toothpaste, when a pile gets sufficiently high, the bottom plastically deforms until it isn't. For a higher mountain range, you need a lower-G planet, like Mars.
- wcoenen 6y ago
  This makes it sound like the elastic deformation at the bottom balances out the forces that are pushing the mountain up. But we know that this is currently not the case, because we observe the Himalayas getting several centimeters taller each year. (For the same reason, we know that gradual erosion can't be enough to counteract the growth.) Hence my assumption that the process of the mountains growing must be reset in a catastrophic manner from time to time. I guess the stresses build up somewhere until an apocalyptic earthquake happens that takes down entire mountains, rather than a gradual toothpaste-like deformation.
  - mncharity 6y ago
    > The Himalayas and the Tibetan Plateau to the north have risen very rapidly. In just 50 million years, peaks such as Mt. Everest have risen to heights of more than 9 km. The impinging of the two landmasses has yet to end. The Himalayas continue to rise more than 1 cm a year -- a growth rate of 10 km in a million years! If that is so, why aren't the Himalayas even higher? Scientists believe that the Eurasian Plate may now be stretching out rather than thrusting up, and such stretching would result in some subsidence due to gravity.[1] EDIT: Gravitational deformation creates a maximum bound near Himalayan height. But actual height below that is apparently a mix of tectonic support from the sides, above-snowline erosion, and boat floating on mantle.[2] [1] https://pubs.usgs.gov/gip/dynamic/himalaya.html https://pubs.usgs.gov/gip/dynamic/himalaya.html [2] https://www.nature.com/articles/d41586-020-01601-4 https://www.nature.com/articles/d41586-020-01601-4 Sci-hub doesn't have the underlying paper yet.
lordnacho 6y ago
Having lived near Regent's park, you have to ask yourself why the birds ever leave. Surely it's clear there's way more junk food than any bird could ever want?

mncharity 6y ago

> limit the height of the mountains Gravitational potential energy becomes sufficient to pay for rock deformation. As with toothpaste, when a pile gets sufficiently high, the bottom plastically deforms until it isn't. For a higher mountain range, you need a lower-G planet, like Mars.

wcoenen 6y ago
This makes it sound like the elastic deformation at the bottom balances out the forces that are pushing the mountain up. But we know that this is currently not the case, because we observe the Himalayas getting several centimeters taller each year. (For the same reason, we know that gradual erosion can't be enough to counteract the growth.) Hence my assumption that the process of the mountains growing must be reset in a catastrophic manner from time to time. I guess the stresses build up somewhere until an apocalyptic earthquake happens that takes down entire mountains, rather than a gradual toothpaste-like deformation.
- mncharity 6y ago
  > The Himalayas and the Tibetan Plateau to the north have risen very rapidly. In just 50 million years, peaks such as Mt. Everest have risen to heights of more than 9 km. The impinging of the two landmasses has yet to end. The Himalayas continue to rise more than 1 cm a year -- a growth rate of 10 km in a million years! If that is so, why aren't the Himalayas even higher? Scientists believe that the Eurasian Plate may now be stretching out rather than thrusting up, and such stretching would result in some subsidence due to gravity.[1] EDIT: Gravitational deformation creates a maximum bound near Himalayan height. But actual height below that is apparently a mix of tectonic support from the sides, above-snowline erosion, and boat floating on mantle.[2] [1] https://pubs.usgs.gov/gip/dynamic/himalaya.html https://pubs.usgs.gov/gip/dynamic/himalaya.html [2] https://www.nature.com/articles/d41586-020-01601-4 https://www.nature.com/articles/d41586-020-01601-4 Sci-hub doesn't have the underlying paper yet.

lordnacho 6y ago

Having lived near Regent's park, you have to ask yourself why the birds ever leave. Surely it's clear there's way more junk food than any bird could ever want?