Galapagos Islands: Erosion fells Darwin’s Arch
bbc.com
bbc.com
I live in the same state as The Twelve Apostles [1], a famous group of limestone stacks on the coast of Victoria, Australia, south-west of Melbourne.
Just up the road, there is a formation that was called London Bridge - a limestone formation protruding out from the land, with two stacks, making it a double-span bridge.
Then one day in 1990, the bridge section adjoining the land collapsed. Two sightseers were on it at the time, though mercifully not on the part that collapsed; they were rescued by helicopter after a few hours.
It just so happened that this collapse occurred during the high school year when we were studying limestone cliff formations in geography class. I remember our teacher impressing upon us that it was a geologically regular and normal occurrence, but infrequent in human life terms, so we were lucky to be able to observe the event just at the time we were studying the phenomenon.
Since then they've called it London Arch [2].
[1] https://explorethegreatoceanroad.com.au/the-twelve-apostles-...
Just a few days before it's collapse, I was climbing on it; well, I couldn't quite get to the Arch part (so I know it's collapse wasn't my fault), but I can't help but think: if it was on the verge of collapse, would it have been able to hold a couple of 150lb monkeys jumping around on it (my buddy and me)?
https://en.wikipedia.org/wiki/Azure_Window
https://timesofmalta.com/articles/view/the-azure-window-lost...
The place with probably the highest density of arches in the world, Arches National Park, doesn't even seem to be sure how many arches it has. Their homepage says "over 2000", while the article https://www.nps.gov/parkhistory/online_books/geology/publica... has a much more conservative estimate of 124...
My take: A quickening erosion cycle could see an accelerated creation of arches, providing the cycle hasn't been altered eg: more top-down erosion.
It could be that an accelerated process is still happening too slow to see new arches. It may also be that climate change isn't strongly manifesting itself this way.
I think increased erosion would also cause arches to fail faster (run through its lifetime at increased speed).
I think there is no limit to how fast an arch can erode (ie. the erosion can easily speed up orders of magnitude) but at the same time I don't think we could be seeing orders of magnitude more arches created, which would be necessary to maintain the number of arches that are now going through their lifecycle faster.
This lets me believe that overall increased erosion would cause less arches to be present at any point in time.
This is just a thought experiment, I have no data to back it up.
Honestly, I visited Galápagos in 2019 and wasn't even aware this arch existed. Might be due to the fact that Darwin & Wolf Islands are two of the smallest islands in the archipelago and located ~ 100 km away from the rest. Plus, they are interesting mostly only for divers, while the other islands offer more varied attractions (turtles, penguins, other endemic flora & fauna, volcanoes, snorkeling, ...).