# Is that an impact crater ESE of the Falklands? **URL:** \ **Category:** Factual Questions\ **Created:** [April 3, 2012, 10:31pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742 "2012-04-03T22:31:26Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [April 3, 2012, 10:31pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/1 "2012-04-03T22:31:26Z")
Looking at Google Maps, there’s a very obvious circular depression about 200 km ESE of the Falklands. Is that an impact crater? Googling indicates suggestions of impact basins antipodal to the Siberian Traps 100-300km in diameter. This is much smaller. Is it a crater created by a meteorite? ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [April 3, 2012, 10:50pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/2 "2012-04-03T22:50:01Z")
On my Google Maps I could see nothing of the sort – can you provide a link? ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [April 3, 2012, 11:19pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/3 "2012-04-03T23:19:59Z")
I’m guessing [this](http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=falkland+islands&aq=&sll=37.0625,-95.677068&sspn=32.66491,81.5625&vpsrc=6&t=h&ie=UTF8&hq=&hnear=Falkland+Islands+%28Islas+Malvinas%29&ll=-52.772863,-54.717407&spn=1.558691,5.097656&z=8). ETA: if you keep going about the same distance again from the Falklands, in roughly a straight line, there’s what looks like another one that hit a ridge. ETA2: as to whether either one is an impact crater, no idea. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [April 3, 2012, 11:27pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/4 "2012-04-03T23:27:16Z")
If you go about 350 km due North of the Eastern end of the islands, there’s a third one. This is fun. 🙂 ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [April 3, 2012, 11:42pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/5 "2012-04-03T23:42:32Z")
Actially, if you look in a straight line from the Falklands through the first one, it looks like there’s a second, but smaller and deeper. As to the OP, looks like it, but I’m no expert in geophysics. ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [April 4, 2012, 12:15am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/6 "2012-04-04T00:15:08Z")
The [Earth Impact Database](http://www.passc.net/EarthImpactDatabase/index.html) lists 182 known terrestrial impact craters, none of which appear to be in the South Atlantic. ---
**Author:** ![JKellyMap](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jkellymap/32/15880_2.png) [@JKellyMap](https://boards.straightdope.com/u/JKellyMap)\ **Post date:** [April 4, 2012, 12:21am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/7 "2012-04-04T00:21:39Z")
You sure that isn’t a seamount? It’s often hard to tell with roughly circular objects, if there aren’t other cues – funny little optical illusion. Look at the shadows of nearby features which are more obviously “higher” or “lower” than the surroundig abyssal plain, and that should help you decide. ---
**Author:** ![SiXSwordS](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@SiXSwordS](https://boards.straightdope.com/u/SiXSwordS)\ **Post date:** [April 4, 2012, 12:35pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/8 "2012-04-04T12:35:27Z")
> [@MikeS](#): > > The [Earth Impact Database](http://www.passc.net/EarthImpactDatabase/index.html) lists 182 known terrestrial impact craters, none of which appear to be in the South Atlantic. IANA Geologist, but 182 seems like a very small number to me. And I think it’s worth noting that of those 182, [only one is not on or very near land](http://www.passc.net/EarthImpactDatabase/Worldmap.html). ([Mjølnir](http://www.passc.net/EarthImpactDatabase/mjolnir.html)) My guess would be that it is more difficult to find and research potential impact sites on the ocean floor. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [April 4, 2012, 1:11pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/9 "2012-04-04T13:11:17Z")
> [@JKellyMap](#): > > You sure that isn’t a seamount? It’s often hard to tell with roughly circular objects, if there aren’t other cues – funny little optical illusion. Look at the shadows of nearby features which are more obviously “higher” or “lower” than the surroundig abyssal plain, and that should help you decide. No, it is a depression - the relief shading is done with a light source from the northwest, as you can tell if you look at [known seamounts](http://maps.google.com/maps?q=falkland+islands&hl=en&ll=21.953236,-159.732971&spn=1.615023,2.617493&sll=37.0625,-95.677068&sspn=32.66491,81.5625&t=h&hnear=Falkland+Islands+(Islas+Malvinas)&z=9). ---
**Author:** ![SiXSwordS](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@SiXSwordS](https://boards.straightdope.com/u/SiXSwordS)\ **Post date:** [April 4, 2012, 1:20pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/10 "2012-04-04T13:20:56Z")
> [@Colophon](#): > > …look at [known seamounts](http://maps.google.com/maps?q=falkland+islands&hl=en&ll=21.953236,-159.732971&spn=1.615023,2.617493&sll=37.0625,-95.677068&sspn=32.66491,81.5625&t=h&hnear=Falkland+Islands+(Islas+Malvinas)&z=9). Just an aside… your link labels that image as “Falkland Islands.” I hope the British don’t try to take _those_ back! ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [April 4, 2012, 1:39pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/11 "2012-04-04T13:39:41Z")
> [@SiXSwordS](#): > > Just an aside… your link labels that image as “Falkland Islands.” I hope the British don’t try to take _those_ back! 🙂 Yeah, that’s a quirk of Google Maps… if you search for a place by name, then scroll manually to another spot and then save the link, it still puts the original search term in the URL. And I was too lazy to snip it out. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [April 5, 2012, 10:05am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/12 "2012-04-05T10:05:24Z")
> [@SiXSwordS](#): > > IANA Geologist, but 182 seems like a very small number to me. And I think it’s worth noting that of those 182, [only one is not on or very near land](http://www.passc.net/EarthImpactDatabase/Worldmap.html). ([Mjølnir](http://www.passc.net/EarthImpactDatabase/mjolnir.html)) > > My guess would be that it is more difficult to find and research potential impact sites on the ocean floor. It takes a rather large impactor to punch through two or three kilometers of seawater to make a crater on the ocean floor. Those are vary rare. Anything that large is probably an extinction-event-type impactor. There probably hasn’t been one that large since Chicxulub (which wasn’t mid-ocean, of course). Note that the one mid-ocean crater actually seems to be on a continental shelf, just like other off-shore craters. Ocean floors are generally much younger than continental plates. If there were mid-ocean large ones from earlier than Chicxulub, they may have been lost to subduction. If they’re still out there, they’ll have been covered in lots of sediment, which combine with the ocean depth to make them hard to find. And note that craters seem to be fairly abundant in North America, Australia, and Europe but sparce in South America and Africa. This is almost certainly a function of where specialists in this subject reside. It’s easier to find and study them close to home. Which means that it’s virtually certain there’s more craters still to be discovered. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [April 5, 2012, 10:37am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/13 "2012-04-05T10:37:34Z")
> [@dtilque](#): > > It takes a rather large impactor to punch through two or three kilometers of seawater to make a crater on the ocean floor. In this case it’s on the continental shelf, so the water is relatively shallow, and it might well have been exposed or only slightly covered during an ice age if South America were more equatorial at the time. ---
**Author:** ![SiXSwordS](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@SiXSwordS](https://boards.straightdope.com/u/SiXSwordS)\ **Post date:** [April 5, 2012, 12:50pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/14 "2012-04-05T12:50:56Z")
> [@dtilque](#): > > It takes a rather large impactor to punch through two or three kilometers of seawater to make a crater on the ocean floor. Again, IANAG, but looking at the Impact Database–which I’m not sure is an exhaustive resource–well more than half the entries are more than 100 million years old. I’m sure everyone has seen [a video representation of the Earth’s changing face over time](http://www.youtube.com/watch?v=cQVoSyVu9rk&feature=related), but it is interesting to compare the ages of those impact craters with the face of the Earth at the time. The Mjølnir impact’s estimated age is 142 Ma. At that time, the area in question would have been very shallow water and could possibly have been exposed land. At the same time, large areas of modern day Asia were exposed land, but we see very few impact sites. > [@](#): > > If there were mid-ocean large ones from earlier than Chicxulub, they may have been lost to subduction. If they’re still out there, they’ll have been covered in lots of sediment, which combine with the ocean depth to make them hard to find. …It’s easier to find and study [craters] close to home. Which means that it’s virtually certain there’s more craters still to be discovered. I agree with everything you’ve said. My main point is that in the same way that we see more craters “close to home” because it is easier (and cheaper) to find and study them, we see fewer impacts in the ocean where they are harder to find, more likely to be disturbed by oceanic activity and far more expensive and challenging to study. There are certainly more to be discovered and the fact that this site is not on the EID does not really tell us very much. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [April 6, 2012, 8:02am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/15 "2012-04-06T08:02:45Z")
OK, it was late at night when I made my post above and I didn’t have my thoughts in order. Here’s what I was trying to say: There are three reason why there are no known mid-ocean (i.e. non-continental shelf) craters. One, which you gave, has to do with how they are found and is thus a systematic error. The other two have to do with how they are formed, and which point to a true scarcity compared to land and shelf craters. One of those is the relative youth of the ocean floors. Somewhere I read that the oldest ocean floor rocks are only 180 million years old. The average is perhaps half that or even less. Since half of all known craters are at least 100 million years old, you can expect that many, if not most, that were formed in the ocean have since been subducted. The other is that at the speeds large meteroites hit, sea water is not significantly different than land. So a meteorite would have to be large enough to form a crater 2 to 4 kilometers deep to make any kind of impression on the mid-ocean floor. That has to be a rather large rock. Meteor Crater in Arizona is about 300 meters deep (counting the rubble filled area at the bottom, but discounting the raised rim), so the rock that caused it would not be large enough. The combination of these two factors probably means there are only a handful of craters on the deep ocean floor. But as **Quartz** pointed out, it doesn’t apply to this potential crater, since it’s on a shelf. ---
**Author:** ![King\_Bobo](https://avatars.discourse-cdn.com/v4/letter/k/c68b51/32.png) [@King\_Bobo](https://boards.straightdope.com/u/King_Bobo)\ **Post date:** [April 6, 2012, 11:00pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/16 "2012-04-06T23:00:46Z")
IAAG, they look to me like “gas-escape craters” which are common on continental shelves and often used in hydrocarbon exploration. Sorry I cannot give a link right now - but many refs available via google. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [April 7, 2012, 5:18am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/17 "2012-04-07T05:18:53Z")
> [@King\_Bobo](#): > > IAAG, they look to me like “gas-escape craters” which are common on continental shelves and often used in hydrocarbon exploration. Sorry I cannot give a link right now - but many refs available via google. They’re a bit big for that, aren’t they? ---
**Author:** ![King\_Bobo](https://avatars.discourse-cdn.com/v4/letter/k/c68b51/32.png) [@King\_Bobo](https://boards.straightdope.com/u/King_Bobo)\ **Post date:** [April 7, 2012, 7:08am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/18 "2012-04-07T07:08:16Z")
> [@Quartz](#): > > They’re a bit big for that, aren’t they? Depends on the amount of gas expelled and the duration of the time gas is expelled to surface. If a very large reservoir is breeched and gas to surface is longstanding with little sediment input into the area, gas craters can be large. Or could be one very huge “gas burp”. It happens. I would look towards this before I looked at a crater from a meteor, especially in an area currently undergoing hydrocarbon exploration. All that said, I cannot rule out a meteor crater - just thinking of something more likely. ---
**Author:** ![King\_Bobo](https://avatars.discourse-cdn.com/v4/letter/k/c68b51/32.png) [@King\_Bobo](https://boards.straightdope.com/u/King_Bobo)\ **Post date:** [April 7, 2012, 7:39am UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/19 "2012-04-07T07:39:48Z")
Missed the edit window. Sometimes seismic surveys will show the presence of gas/oil “chimneys” below some of these depressions. Depending on the geology they can be bad news for hydrocarbon exploration as they may show a badly breeched reservoir where most/all gas or oil has escaped. Not good. In other cases, with more geologic compexities good reservoirs may still exist. It is a bit of a crap shoot. Thankfully, that is where I have something to offer. I get to look at a whole lot of “stuff” to see if it is still worth a bit more exploration. Ahhh - O&G exploration - my life! ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [April 7, 2012, 2:07pm UTC](https://boards.straightdope.com/t/is-that-an-impact-crater-ese-of-the-falklands/617742/20 "2012-04-07T14:07:52Z")
Thanks for the info, **King Bobo**. After your first post, I did some Searching to see if there where any images of Gas-escape craters, but couldn’t find any. You don’t happen to know of any, do you?