Your closest comparison here is the Himalayas

The Geological Society says on this:

The Himalayas are still rising by more than 1 cm per year as India continues to move northwards into Asia

That rate of rise gives you 10,000metres/million years. Limited by the rate of erosion, but your high speed mountain target is reasonably achievable.

It's possible that mountains could pop up very quickly (on geological timescales).

Two new studies by a University of Rochester researcher show that mountain ranges rise to their height in as little as two million years

"Deblobbing" may not sound like a very scientific word, but it's the term given to a dense root beneath the Earth's crust—a blob—that becomes unstable and begins to flow downward into the earth's mantle under the force of its own mass, until it detaches. When two tectonic plates collide, such as the Nazca oceanic plate in the southeastern Pacific colliding with the South American continental plate, the continental plate usually begins to buckle. Floating on a liquid mantle, the plates press together and the buckling creates the first swell of a mountain range.

 

Below the crust, however, there also is a kind of buckling going on in the solid portion of the upper mantle. This dense mantle root clings to the underside of the crust, growing in step with the burgeoning mountains above. This dense root acts like an anchor, weighing down the whole range and preventing it from rising, much like a fishing weight on a small bobber holds the bobber low in the water. In the case of the Andes, they swelled to a height of about one kilometer before the mantle root beneath them disconnected and sunk into the liquid mantle. The effect was like cutting the line to the fishing weight—the mountains suddenly "bobbed" high above the surrounding crust, and in less than 3 million years, they had lifted from one kilometer to roughly four.

Your closest comparison here is the Himalayas

The Geological Society says on this:

The Himalayas are still rising by more than 1 cm per year as India continues to move northwards into Asia

That rate of rise gives you 10,000metres/million years. Limited by the rate of erosion, but your high speed mountain target is reasonably achievable.

It's possible that mountains could pop up very quickly (on geological timescales).

Two new studies by a University of Rochester researcher show that mountain ranges rise to their height in as little as two million years

"Deblobbing" may not sound like a very scientific word, but it's the term given to a dense root beneath the Earth's crust—a blob—that becomes unstable and begins to flow downward into the earth's mantle under the force of its own mass, until it detaches. When two tectonic plates collide, such as the Nazca oceanic plate in the southeastern Pacific colliding with the South American continental plate, the continental plate usually begins to buckle. Floating on a liquid mantle, the plates press together and the buckling creates the first swell of a mountain range.

Below the crust, however, there also is a kind of buckling going on in the solid portion of the upper mantle. This dense mantle root clings to the underside of the crust, growing in step with the burgeoning mountains above. This dense root acts like an anchor, weighing down the whole range and preventing it from rising, much like a fishing weight on a small bobber holds the bobber low in the water. In the case of the Andes, they swelled to a height of about one kilometer before the mantle root beneath them disconnected and sunk into the liquid mantle. The effect was like cutting the line to the fishing weight—the mountains suddenly "bobbed" high above the surrounding crust, and in less than 3 million years, they had lifted from one kilometer to roughly four.

Your closest comparison here is the Himalayas

The Geological Society says on this:

The Himalayas are still rising by more than 1 cm per year as India continues to move northwards into Asia

That rate of rise gives you 10,000metres/million years. Limited by the rate of erosion, but your high speed mountain target is reasonably achievable.

Your closest comparison here is the Himalayas

The Geological Society says on this:

The Himalayas are still rising by more than 1 cm per year as India continues to move northwards into Asia

That rate of rise gives you 10,000metres/million years. Limited by the rate of erosion, but your high speed mountain target is reasonably achievable.

It's possible that mountains could pop up very quickly (on geological timescales).

Two new studies by a University of Rochester researcher show that mountain ranges rise to their height in as little as two million years

"Deblobbing" may not sound like a very scientific word, but it's the term given to a dense root beneath the Earth's crust—a blob—that becomes unstable and begins to flow downward into the earth's mantle under the force of its own mass, until it detaches. When two tectonic plates collide, such as the Nazca oceanic plate in the southeastern Pacific colliding with the South American continental plate, the continental plate usually begins to buckle. Floating on a liquid mantle, the plates press together and the buckling creates the first swell of a mountain range.

Below the crust, however, there also is a kind of buckling going on in the solid portion of the upper mantle. This dense mantle root clings to the underside of the crust, growing in step with the burgeoning mountains above. This dense root acts like an anchor, weighing down the whole range and preventing it from rising, much like a fishing weight on a small bobber holds the bobber low in the water. In the case of the Andes, they swelled to a height of about one kilometer before the mantle root beneath them disconnected and sunk into the liquid mantle. The effect was like cutting the line to the fishing weight—the mountains suddenly "bobbed" high above the surrounding crust, and in less than 3 million years, they had lifted from one kilometer to roughly four.