Earth's mountains form in millions of years, Moon ones near instantaneously | Hacker News Reader

Earth's mountains form in millions of years, Moon ones near instantaneously

jatan.space

90 pointsuncertainquark27 comments

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Mountains on Earth are formed by tectonic shifts and volcanic eruptions, which, yes, take millions of years.

Mountains on the moon (aka: crater walls) form nearly instantaneously because of a violent impact.

You can make instant mountains on Earth too. Downside is, it'll probably kill off most life on the planet.

We have a few craters already, e.g. -

https://www.meteorcrater.com/

A bit frustratingly, they mean "geologically instanteously" which is not the same as "instaneous as per human perception".

I'm not sure how long rock takes to cool after an asteroid impact, maybe days, maybe months or years depending on how large of an impact and how cold the surroundings (no atmosphere soooo....)

These mechanics are not discussed in the article and are instead just dismissed as "negligible"

Wouldn't molten rock simply flow and flatten? Even if not yet rigid, I'd assume the mountains do effectively form instantaneously (i.e. seconds or minutes), possibly flattening some as they slowly cool.

EDIT: The PBS NOVA special "The Day the Dinosaurs Died" describes the mechanics of the Chicxulub impact starting at about the 33 minute mark. It's as instantaneous as one would intuit, given the magnitudes involved:

> NARRATOR: The asteroid had punched a hole nearly 20 miles deep, gouging a crater 124 miles wide. Over 40,000 cubic miles of rock were displaced, rising into towering mountains.

> JOANNA MORGAN: So, this is an absolutely amazing event, because that happened in less than two minutes, and if you think of it, mountains the size of the Himalayas were formed in seconds.

> NARRATOR: As the mountains collapsed, they formed what's known as a "peak ring," found only in the largest of super craters. It's the only peak ring left on Earth; the next nearest is on the moon.

https://www.pbs.org/wgbh/nova/video/day-the-dinosaurs-died/

See, now this is an enjoyable fact. It is interesting to think that all of the forces involved in the collision will finish propelling themselves into each other within 2 minutes. One would think that it would be a little bit longer than that, because the transfer of energy between two cars in a car crash is over in a few seconds. But an asteroid colliding with a planetoid seems like it would take longer, given the amount of mass involved and the amount of deceleration that needs to take place (x km/s to 0.0000000 km/s)

Another cool fact: IIRC, the heat was so intense it basically incinerated all flora and fauna across distances that effectively encompassed most of the Americas. The rest of the planet burned more slowly, relatively speaking, as material fell back from outer space and forests burned in a planet-wide conflagration.

If you liked that, also listen to radiolabs 'dinopocalypse'. it's on YouTube as well.

Another interesting fact, some of the ejecta from that impact went as far as the moon!

> Wouldn't molten rock simply flow and flatten?

Flattening is a battle between gravity and a material's binding energy. The Moon's mass permits steeper slopes with similar material. (There are still limits, of course.)

They want me to pay $25 to watch something my tax dollars already paid for?

Edit: Nevermind, there's a torrent.

US federal tax dollars no longer fund a significant portion of public broadcasting. Only about 1/7th is federally funded.

If 1/7th that doesn't entitle me to watch it, it should be 0.

Sorry, I didn't realize there was a paywall/geo-block. It works for me in Chrome Incognito after confirming that KQED is my local affiliate, so it might just be regional.

(I do donate to KQED, partly so I can access PBS TV on Roku, but account login is just... I don't have the words... so I don't actually login on my computer, and my Roku account link invariably, mysteriously deactivates sometime between the last time I watched something and the next time I want to watch something.)

That drove me a bit batty. I skimmed the entire article for a time estimate, and am now in a negligibly worse mood for it.

Geologically negligible, or? :)

This article is barely mentions formation of mountains on Earth. The article is almost entirely about lunar craters, lunar central peak craters, and lunar peak ring craters.

Interesting article, terrible headline.

It's editorialized. The original title of the article was changed from this:

"Exploring the marvel that are mountains on the Moon"

The craters are interesting, but one of my favorites is the “cosmic thunderbolt” theory for the gigantic gash on mars (Valles Marineras)

https://www.thunderbolts.info/tpod/2005/arch05/050408mariner... (Link warning, use gigantic grain of salt and a hard sceptic hat...fun nonetheless)

> This article is barely mentions formation of mountains on Earth.

Isn't that pretty well understood already?

They both are.

It's interesting how my mind had some trouble processing some of those crater images, because I saw initially some of them as circular buttons, going up from the surface, instead of craters going down.

I had to stop looking, and look back several times before my mind could actually see some of those pictures correctly.

It has happened to me since I was a child, at the time of Apollo. My trick was turning the photo upside down so the light aligned with the room source.

Same. One in particular still looks like a button for me.

I can't imagine the size of object that formed the Valhalla crater on Callisto. The central region is 360km across, and the diameter of the entire basin is 3,800km. That's a distance on earth from LA to Arkansas!

And the whole equator of Callisto has a circumference of 15,100 km. Proportionately, that would be a basin the size of the Indian ocean!

The second one is an amazing close up photo of a lunar mountain.

There are mountains on earth that formed in a few years too, and in fact most mountain ranges form pretty quickly as far as geology goes.

Now I want to hike a mountain on the Moon. My Instagram needs new content.

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