r/geography • u/apprehensivefart • 3d ago
Physical Geography Possible crater formation in Northwest Madagascar
I've been browsing around the world using this great website that uses an automatically adjusting relief map of the world, and may have come across something interesting.
This formation is situated in the Marovoay District, Madagascar. Other craters in Madagascar have been explained as basalt intrusions, but I'm unsure if this feature has been assessed already. It appears to stand out from the surrounding topography, and I haven't found any mention of it elsewhere.
The crater floor is roughly at 30-40m elevation, while the central peak rises to around 94m. Its width is around 2.8km. I've read that a central peak is rare in an impact crater of this size, so perhaps an alternative explanation is more likely. It would be exciting if this turns out to be an impact crater, but I could see how other explanations may fit its features.
Here's what the area looks like in Google Maps.
In any case, using this relief map website does allow for impact crater discovery. I was browsing around Northwest Australia a few days ago and found what looked like a crater. It turns out the discovery of the crater was only announced last year! So the potential is there.
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u/Burner17273_ha 3d ago
Here to be in the screenshot if this ends up in a publication, HI MOM!
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u/mulch_v_bark 3d ago edited 3d ago
After a quick peek at some maps (e.g.), I’m skeptical but open to being surprised. It’s on the Antanimena Plateau, part of the late Cretaceous flood basalt province that’s been heavily weathered (obviously!) and would be likely to show eroded volcanic vents. I’m also a bit suspicious about getting a clear central peak that resists erosion so well on that substrate, but I’m no craterologist. These factors make me suspect we’re seeing old traces of volcanism showing through erosion. I’m not saying it’s not interesting or not worthy of further investigation, to be clear.
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u/SomeDumbGamer 3d ago
Easiest way would be to see what the soil/rock composition is like.
If it’s volcanic then the center island would be basalt or some other volcanic rock.
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u/gabisfunny 2d ago
My 2 cents on this. It is important to mention that I don't work with impact craters, but I've worked with a person who knows about it. 2.8 km in diameter would be the lower limit for a crater develope a central uplift, and it would probably be very small compared with the total size of the crater. So, in my opinion, it's unlikely that this is an impact crater. However, I wouldn't rule out this possibility, at least, not just by this image. My suggestion: send the information and location to some experts in craters, like Dr. Gordon Ozinsk or Dr. Ludovic Ferriere and listen what they have to tell you. These guys are always very very busy, and they receive TONS of photos of possible craters every day. Their answer will probably be something like "possibly yes" or "possibly no", and consider yourself lucky if they elaborate further. I think that, in case of doubt, it is always worth trying and talking to those who really understand, but it's also important to understand that their opinions are based on a whole life of experience in the subject, so trust their answer. If there's 1% of chance to be, they will certainly look carefully into it.
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u/Total_Philosopher_89 3d ago
What's the scale here mate? Approx width of crater. Cannot find scale/distance on "this great website".
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u/EpicAura99 3d ago
OP says in their post, 2.8 km.
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u/Total_Philosopher_89 3d ago
I know what they say. I'm just trying to work out how they came to this measurement.
I'm not doubting OP at all just trying to understand.
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u/MalemPO_king 2d ago
Is that the same Impact that Vox made a video on?
If not it's strange Madagascar has 2 Craters
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u/Qwertysapiens 2d ago
Madagascar is the world's 4th largest island, a little smaller than Texas. It's maybe a little unusual to have two such craters, but it's also a pretty big region.
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u/MalemPO_king 2d ago
Ok it's not the Same crater
Are craters like these not uncommon? Two in Madagascar seems very very lucky if not
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u/gregorydgraham 2d ago
The Earth should be covered in craters, so not finding them is a function of funding and weathering
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u/KebabGud 2d ago
first i have to say that i loved the website.
Scrolled around the world a bit and i just discovered how big the mountains of western Yemen are.
I had no idea.
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u/Worldly-Cherry9631 2d ago edited 2d ago
That website is so much fun, especially they ways to play with the overlays and how fluid it feels.
Thank you for sharing!!!
Oof what's going on with the datasets at the Dutch-German border? https://relief.bertspaan.nl/world?lang=en#9.08/52.0864/6.7992!a1,49,MCkJAqegI~15*s
The German side looks higher res and to ignore trees, while dutch side looks like and older lower res AHN with treetops (ie not "maaiveld" dataset), but that doesn't go all the way to the border.
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u/GeckoNova 3d ago
Oh please oh please let this be a super cool discovery 🙏