[JohnnyMorales (OP)]

When i searched on google, I could not find any information on this structure.

Thoughts?

[damocles]

It is part of the way that our brains are wired that we try to see patterns in every picture or story, and when we think we find one, we tend to sub-consciously force fit the rest. I think that this one might also be an optical illusion. When I look at that picture I can see two features that might, just plausibly, be circular: a semicircle of rocky islands to the North, or a whitish region of shallow water to the South-West.

But when I first looked at this picture I saw that the label "Great Slave Lake" should really be "Eire", because I could see lighter coloured regions representing the Irish Sea and the Bristol Channel, the hump of Wales and the toe of Cornwall in darker colour, and Kent and Essex at the right extremity of the picture. The semicircle of rocky islands would have a centre somewhere near Sheffield!

[JohnnyMorales (OP)]

yes, but that is a semi-circle without a doubt. I don't think anyone has to rely on the natural desire to see patterns to see a semi circle there.

In any case the phenomenon you speak of is NOT one of isolation.

It is in a sea of shapes Etc., that our mind will see patterns.

There mostly water with a semi-circle in this picture. Imagination isn't necessary.

Perhaps it was more difficult for you, because I was forced to lo-res. the photo in order to get it under the size limit for images on this forum.

If you actually visit the location on google earth, it might actually be more clear.

[damocles]

All right then. I am no geologist and a mediocre geographer. When I see a semicircular feature I think three things -- impact crater, caldera, moraine. Looking at those three things, impact crater is possible, but the least common. Caldera seems unlikely, because the rock does not look like any volcanic rock I know (but no expert, as I say). Moraine? Well, if you look at the islands in the centre, they are long and narrow, and near parallel, as though they once had flow channels between them. The islands at the termini of the semicircle are much rounder and not particularly aligned. Maps of the area suggest that the predominant flow direction in the last ice age was North to South. I would tentatively suggest moraine as the most likely explanation, but we really have to wait for a geologist to join the thread.

[JohnnyMorales (OP)]

a moraine is unconsolidated material.

What you are seeing in the photo is all basically bare bedrock including the semi-circle, because you are looking at part of the Canadian Shield - as the wiki says - The North American craton is the bedrock forming the heart of the North American continent and the Canadian Shield is the largest exposed part of the craton's bedrock.

When it comes to round land forms that are natural craters are not rare, but CONFIRMED craters are rare.

Confirmation requires several different things be found at the site.

If nothing known to be a result of an impact can be found then other explanations are used as in the semi-circle formation in the Hudson Bay to the East of this.

Confirmation is NOT free. To actually send out a team to simply prove or disprove an object is an impact site can be prohibitively expensive especially when it's to a location as remote as the Great Slave Lake.

Without greater justification it's not going to happen. So it's nature is left undetermined.

Undetermined is NOT the same as NOT being something.

While there are quite a few landforms that could very well be impact sites, most go undeclared, because no mission has been set up specifically to prove or disprove this.

Probably the vast majority of "confirmations" re impact sites were the result of work being done in a location for reasons UNrelated to proving it was an impact site, like searching for oil or other minerals to exploit. While doing that work, a keen eyed geologist would notice that the rocks they were examining exhibited evidence associated with an impact.

That's how the totally UNDERGROUND impact sites are found with sheer luck, not purpose.

So your skepticism based on the "rarity of impacts" is not justified.

If you note I said PERHAPS in my headline.

I did not say I knew either, but that the shape reminded me of several well known craters have been confirmed also located in the Canadian shield. Do a search for clearwater lakes meteor crater and you'll see the extreme similarity.The parallel striations you think so important are found on quite a few meteor craters of great age. If anything that's more evidence that it probably is (Arounga, Gosse's Bluff.

If you had taken a moment before you decided I had to be wrong to look at them you'd be hard pressed to deny the similarity in appearance.

Considering that the shape of this object conforms quite nicely to those craters that have been confirmed in that location to think this might be another impact site is not far fetched at all.

Oddly the option you quickly dismissed that it might be volcanic in origin is also far better than a moraine or anything else, for as the fullwiki says - The Shield was originally an area of very large mountains (about 12,000 metres or 39,000 feet)[7] with much volcanic activity, but over the millennia the area was eroded to its current topographic appearance of relatively low relief. It contains some of the most ancient volcanoes on Earth. It has over 150 volcanic belts (now deformed and eroded down to nearly flat plains) that range from 600 to 1200 million years old.

It could very well be a submerged caldera with only part of its rim showing, but if it is, it is one of the roundest ones in evidence.

To demonstrate how "round" the semicircle is I doubled it and stuck it together in paintnet.

[damocles]

a moraine is unconsolidated material.

What you are seeing in the photo is all basically bare bedrock including the semi-circle, because you are looking at part of the Canadian Shield - as the wiki says - The North American craton is the bedrock forming the heart of the North American continent and the Canadian Shield is the largest exposed part of the craton's bedrock.

I do not have enough resolution in Google Earth to clearly see whether the material in those islets is consolidated or not. Certainly it looks like Canadian shield material, but whether bedrock or gravel is not clear in the images.

When it comes to round land forms that are natural craters are not rare, but CONFIRMED craters are rare.

Confirmation requires several different things be found at the site.

If nothing known to be a result of an impact can be found then other explanations are used as in the semi-circle formation in the Hudson Bay to the East of this.

Confirmation is NOT free. To actually send out a team to simply prove or disprove an object is an impact site can be prohibitively expensive especially when it's to a location as remote as the Great Slave Lake.

Without greater justification it's not going to happen. So it's nature is left undetermined.

Undetermined is NOT the same as NOT being something.

Agreed. But... while impact craters may be quite numerous, there is a big difference between this site and sites in the Arizona desert or Northern Australia. The latter areas contain a record of impact craters, far from unblemished, but still discernible over perhaps a few hundred million years. Northern Canada has suffered at least three major glaciations in less than the last million years, and there is nothing like ice for obliterating features of the pre-existing landscape! If we are looking at an impact crater it would probably have to have been formed since the last ice age to be in such good shape -- a window of a mere ten thousand years. On a scale of ten thousand years, as opposed to a hundred million years, impact craters almost certainly are a rarity.

I take no issue with the rest of your post, which makes a lot of sense.

[JimBob]

WELL, Peeps

i think the lot of you  may be on the wrong track - (Sorry Slavic Dance)

Please answer the following True or False question:

T __; F __  Canada is a major source of diamonds.

(it is True) Thus - this is probably a sedimentary rock, deformed by a volcanic pipe that was in the middle of the circle of rocks. The diamond mines are near Great Slave Lake so ..... this is most likely a Kimberlite Pipe. A Kimberlite Pipe is an erosional feature, formed when a volcano is formed, then is eroded below the ground base of the volcano. It is a remnant of the vent through which the lava flowed to the surface.

That is what we are looking at here. See " Transport from mantle" on the Wikipedia page http://en.wikipedia.org/wiki/Diamond . The illustration on the right of the sub-header in quotes, above' shows what a pipe is, how it is    formed and where the diamonds occur. They are part of the material included in the term "xenoliths" as labeled on the diagram.

[Airthumbs]

I have to say that in response to the above post which I thought seemed to provide an excellent possible candidate for what this structure might be I undertook a little bit of research.

Now kimberlite pipe....... my understanding of these features is not a hollow pipe at all but one that consists of a solid core of hardened molten material.

I am no expert on geology but I would expect that a pipe like this would not erode from the centre but that the erosion would take place initially at the outer perimeter.  I might be wrong but I suspect that this formation is actually several pipes in close proximity.  Maybe that is what Jimbob meant but I just misinterpreted it.

[Bass]

Kimberlites exist in the Great Slave Lake region, and kimberlites do form craters with rims when they explode onto the surface.  Kimberlites and lamproites erode easily, which is why they are hard to find.  In fact there is a known kimberlite on the east shore of the lake about halfway between the "crater" islands and Yellowknife.
That being said, I don't think this structure is a kimberlite.  For starters, it's too big.  Most kimberlites are 1 km in diameter or smaller, this structure measures closer to 10km.  The area has obviously been scoured by glaciers, which would have eroded off the original crater rim.  Also, the area east of the Yellowknife metavolcanic terrain is mostly granitic craton material.  If you expand Google Earth, there are several circular granitic domes that are visible.  My guess is that the circular structure is likely the resistant remnants of a granite dome.
One thing I've found in my geologic career is that Mother Nature is random- and doesn't create regular shapes like circles, arcs and straight lines unless there is an underlying geologic/tectonic reason.  In other words, I pay attention whenever I notice obvious circular structures.

[MOON TRUTH]

This is one of my favorite locations on the Earth. I have never been there, but I do know a little something about this circle pattern you talk about. I hope you are ready for this, because most people are not. The circle pattern you see, are you ready? Okay! The pattern is created by the Mare Orientale crater on the Moon. Go ahead and laugh, most people do. But I wouldn't say it, if I couldn't prove it. I do reverse image overlays of the Moon Surface, over the Earth's surface, using Google Earth. I use the USGS drawing of Mare Orientale, flip it and overlay it over this spot. I am telling you, right now, believe it or not, this crater on the Moon, basically shapes every continent on the Earth. I know that scientist says it's impossible, If you want to believe them, go ahead! But I highly recommend that you investigate this for yourself. You are not going to believe what you find, at first, then you will have no choice, because you will see it so clearly. I have been doing this for 2 years, and I know, that if the maps are correct, the Moon has impacted the Earth, at least 8 times, for sure. I use the weather patterns to confirm it. I have also used the patterns, to actually find impacts. Here is something else you can laugh at, You will find that the Moon is 3X the size we are told. Laugh it up! Watch my video on youtube, titled: Common Sense - Geologic History of the Earth and Moon. I know you would think that if I were right, we would all know this, right? Knowing this, points you to the resources on the Earth, like gold, need I say more. It's up to you, check it, or don't! You will learn, just how funny it's not. I am not joking around. You asked, and there is your true answer. It's actually ancient knowledge. The Moon is the Destroyer. I hope you look, because you seem very interested in this spot on the Earth. Another tip, it all seems to take place in the Pacific Ocean, guess where, all the subduction areas, including the Marianas Trench, Hmm, Don't figure does it? It all becomes very obvious, once you get past the denial part of it. Have Fun. If you have any questions, just ask.

[MOON TRUTH]

The structure, call it what you want, is an impact center, formed by the Mare Orientale crater on the Moon. This impact, and the resulting super volcano, is probably what created most of Canada. The Great Lakes are also huge volcanic openings, from the same exact crater, different impact. Same with the Caspian. Use your common sense, and put the puzzle together yourself. Mare Orientale is the key. It used to face the Earth. Just like the side that faces us now, is the side that hit Earth last. Do you really want to know where this one can be clearly seen on the Earth? Okay! Just look at the huge circle that surrounds Indonesia, part of China, it's about 2700 miles in diameter. That is Mare Imbrium. Just get an image of it, and flip it over, then place it over this circle, using Google Earth. Here is where you will also discover the true size of the Moon, 3 X, you'll see. Let me know how it goes.

[MOON TRUTH]

Okay, I had this Great Slave Lake, positioning itself perfectly again, and confirming :X itself as a center of an impact. Mare Orientale, again! With this alignment of MO, we can see Alaska clearly in place. It shows the Hawaiian Islands. Then the weather patterns will always confirm it over time. I just placed Copernicus in Northern California, with almost every detail in place. I uploaded a video on youtube - titled - Copernicus crater moon impact Northern California - It's not to bad, I remain fairly calm. Unless you already know, I highly recommend opening your mind to this theory. I admit I am not very good at explaining myself, but I have put a lot of time into this, and there is more to it, than people want to believe. I will try not to waste peoples time. Lets keep this discussion open. I will always try to keep my comments friendly. I may criticize main stream science occasionally, someone has to do it! If their theories are correct, it shouldn't be very hard to prove me wrong, on this subject. After all, I am only one man, challenging many, very smart people.

[RD]

Again "self-similarity" can explain the phenomenon you have observed ... https://en.wikipedia.org/wiki/Self_similarity

If you find that some parts of Earth when scaled / rotated / flipped resemble other features on Earth then bang goes your "our-moon-is-much-larger-than-advertised-and-repeatedly-bounces-off-earth-leaving-imprints" theory.

Don't feel too bad about your misconception : "smart" astronomers have made similar errors ... http://www.skyandtelescope.com/news/3306251.html?page=1&c=y