He did a video on this topic already ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-E8YeGy5Ak8k.html Basically the lava was a hotter cousin to basalt incorporating minerals that have already cooled and crystalized out of basaltic melts which was possible back when Earth's interior was hotter than it is today. The youngest example of this kind of lava was related to hotspot volcanism in Africa some 90 million years ago if I remember correctly.
If I recall correctly, komatiite is a lava that originated in the mantle of the earth with ultramafic minerals like olivine and pyroxene in it. Compared with basalt, komatiite has a high melting temperature, higher than those produced in the shallow mantle today, because Earth was hotter than it is today and the more recent geological eras. So, komatiites will not form in today's volcanic events, an exception to the general pattern in which geological processes we see today also took place throughout Earth's history. I think they're one of the more interesting phenomena of geology, and one of the reasons I like studying the field as an amateur.
The glaciation is what put the lakes there, but why the lakes ended up where they did is due to the underlying geology. So in a way, both are correct assertions.
There is also the fact that due to the last ice age melting, which because of the thickness of the ice crust (Iirc, as an exemple, there was about 2 km of ice over the Laurentides, the region I live in in Eastern Canada, and is now way below the modern arctic region), resulted in incredible amount of erosion due to the displacement of surface water. So by the time the flow hit the ground, it was so strong that it effectively carved into the bedrock and swept away huge multi-tons boulders like they were pebbles (you can still find to this day huge smoothed boulders in the middle of forests, or just below the surface, right in the middle of forests or elevated area that obviously never were river bottoms), causing the formation of fjords all over the land, as many of the rivers that cover the area have a form reminiscing of more evident jfords like those found in the Scandinavian peninsula (if you were to take a cross section, it would be shaped like a T, where the shores are shallow but the middle has great depth which hide a great flow of water, which make them especially dangerous to swim in if unprepared). Even a simple walk in the forest can show you parts of the bedrock still visible, as the accumulation of biological matter has yet to recover the land in dirt in many places. I wouldn't be surprised that the difference in height between the Canadian shield and the western mountain ranges funeled the flow, with the areas now known as the great lakes to be the result of interaction with water soluble rocks and the aforementioned ice age melting water flows, creating pockets of water whereever the flow was throttled due to the local bedrock composition. As an end note, I'd really like to hear you speak of the odd geological formation found within the Hudson Bay, the Nastapoka arc, as its almost perfectly circular shape always piqued my curiosity, and has been a source of debate among geologist for ages. Its as if something just took a planet sized cookie cutter and stripped away a whole chunk of the landmass, with despite its shape insinuating its origin to be an impact crater, geological analysis found no shatter cones or melted rocks whatsover. I'd like to hear your take on the matter.
The parts of Ontario I've lived in were almost all composed of glacial debris with no discernible pattern to it. I grew up on the Oak Ridge moraine and now live on the bottom of a former glacial lake just south of the edge of the Shield. There are escarpments from sea shores when the land was depressed under the ice, and we get the occasional earthquake because the land's still rebounding. We're basically the dump where the glacier dropped everything it scraped off the Shield.
I'm on the bruce peninsula which is on lake Huron. Behind my old house there's a massive granit Boulder that was in the shape of a ball and taller than me. In that area there's like 30-60 centimeters of top soil and that's it
I live along Lake Ontario and I’ve been to Great Slave Lake as well as Great Bear Lake , I have been subscribed for a while and I always look forward to seeing your next upload. Best regards as always from Lloyd somewhere here in southern Ontario Canada 🇨🇦.
It's cool to see a video about these types of larger, continent-scale geologic features and forces and their geologic histories. Would love to see more videos covering larger features and their changes over geologic time, like the Wester Interior Seaway or the Tethys ocean, or the assembling of western North America. You condense complex topics down so well into small bites. Thanks for your great work.
Not to shade GeologyHub, but there's a 3 part Nova called, "Making North America", hosted by Kirk Johnson. It does an excellent job of describing the major events on how North America was formed (geologically and inhabitation) in less than three hours. I was very impressed with that series...
Big fan of the work you put out, I never miss an episode Canadian geology is fascinating, I was wondering if you could do a video on glacial erratics, particularly the abnormally large glacial erratic I grew up nearby to called “The Big Rock” in Okotoks, Alberta Also, and this isn’t a problem just so you know for the future, Winnipeg is pronounced “win-uh-peg” not “whinnie-peg” Cheers, keep it up!! 👍👍
@@SunsetLynxx - I've been around it, but never in it. Hitchhiking in the 70's, that was like the gateway to civilization when going East. After days of flat nothing with pickups swerving onto the shoulder to scare you and beer bottles flying out of car windows at you, you pass Winnipeg, and the trees start and the wind ends.
Check out Lake Vättern in Sweden. It's a deep, narrow lake that was formed as a grabben along the Protogine zone. The geological map along this zone is really interesting.
I was literally googling the largest lakes in the world last night and saw many in canada. As a new resident to canada I wondered why there were so many. Thank you. Now how about a video on nittilling lake? I enjoy these geologic videos as much or more than the videos on volcanoes.
Until about age 9 I lives in Kenora at the northern end of lake of the Woods. There is farming to the west in Manitoba but right there it's bare rock, small trees and muskeg. No farming but a great area for picking wild berries.
Flying from Ireland to NZ on my return trips to catch up with family etc. I’m often amazed at the share size of Hudson Bay when flying over. Some Bay!!
I saw a video of yours one night while surfing youtube for content to soothe me to sleep. Your voice and how you break down the information hooked me to subscribe. While a lot of the things mentioned I have no idea about - and I rewatch them several times to wrap my head around them - it's still exciting and intriguing to learn about, and I've always enjoyed learning about Geology. I appreciate your time and the content you put together. I look forward to your future videos! Thank you!
@@brian8410 hmm, I wasn’t aware in my comment that I said they cured my insomnia… It started off as a night I needed help sleeping and it turned out to be a wonderful find, so now I actually watch these videos to learn instead of helping me sleep. Happy learning, take care :)
Thanks for this post. I have been fasinated by this area - the Canadian Shield - and these lakes for years. I knew they were in a line but never made the connection.
Finally a video that talks about Bear and Slave lakes. These are part of the rift that is slowly forming as Canada is slowly being pulled apart by tectonic action.
The lakes also occur because the vast continental glaciers scoured the Canadian shield down the the bedrock and then dug down even deeper into the softer terrain just off the edge of the Canadian shield.
Eight million square kilometers of some of the oldest and hardest rock on the face of the earth. Scraped clean of topsoil by repeated glaciations. Cape Cod and Long Island as well as the highest points of a half dozen midwestern states are apparently the terminal moraine that glaciers scraped off the region
As a note the Great Lakes are connected to each other. The water flows from northern and northwestern Ontario into Lake Superior down the other lakes to the Atlantic Ocean. The other lakes you mention in western Canada flow to the Arctic Ocean.
I make a trip with a friend to Winnipeg and Winnipeg Lake decades ago. My friend, a French major in college, wanted to practice his French in that area of the city. Interesting geology in the area.
I loved this and would love to learn more from you about cratons. I visited Karijini National Park in Australia and stood on a rock surface that was over 2 billion years old. Beautiful surroundings there, and great experience. I believe the park is part of the Vaalbara craton. Not sure about the name, but the other half of it is stuck in South Africa. I bet you know the one I mean 😅 Thanks for all your great content!
Please do a video on komatiite. I've never heard of this and I'm very interested! Why aren't circumstances on earth allowing for this kind of lava flow at this time? Really hope you follow up on this! Thanks! Love your videos and watch every one!
I thought before the most recent Ice Age, the Missouri River emptied into the Hudson Bay in an Amazon-esque fashion. But the Glaciers advanced, and redirected the waters towards the Mississippi and Mackenzie. My understanding was those Lakes were remnants of the vast river system that existed so long ago.
I feel I learned a number of things from this video, including why the lakes formed along the shield's boundary, but not why in a straight line rather than in an arc.
I live on the shield. In something called 'The escartment'. Were ancient mountains are worn down to large hills. I can see it every direction in my small but sprawling city. My sister moved to BC. I could not handle the stress of earthquakes so i wil stay on the shield thnx. XD
In high school geography, I once ask the teacher why were these lakes were in a line. He didn't have an answer, but I knew there must be one. I had figured this was the reason, but it's nice to have it confirmed.
So I see you left Minnesota’s Arrowhead and Mesabi regions out of the Canadian Shield, does the international border actually follow the edge of the craton, with NE MN geologically different? Or was it omitted just for simplicity?
Would love to hear more about the Canadian Shield. I live in southern Ontario, and often find tonnes of tiny seashells and coral fossils in driveway gravel that has been sourced locally. I wonder how old they are. I've also heard that it is very hard to find any other "big" fossils because of this.
I grew up right on that line north of Kingston by Lake Ontario. It was really obvious - abruptly going from cottage country exposed granite to limestone farmland whenever we travelled into town. There was a small ski hill right on the line because of the huge change in elevation.
Neat summary. Have a question do you think that the radius of the graphic you used could be a foot print from a meteor strike. The sudden shock could have melted ice rock and there’s recently been a miner in Canada? I think that’s been finding mastodon tusks and bones, not the point but it could explain it better why the animals herd and and ultimately died. They say the Great Lakes formed as result of volcanic tubes being crushed by glacier’s forming over the top and eventually collapsed and they filled in with water. Might explain the copper and gold found.
I understood you saying Cratons had generally straight edges but I don’t see how that explains the Canadian and US Great Lakes existence. I’ve often wondered if the land east and west of the lakes pulled apart creating the deep cavities the lakes seem to be covering. Can you tell us what processes most likely formed the lakes as opposed to my guess? I appreciate you making the videos. I have in fact wondered how all the Great Lakes formed but never had an opportunity to ask anyone before. Thank you!
I'd never wondered about this; nevertheless, I did find it interesting. Is the "Canadian shield" also called "Laurentia" on some maps of plate tectonics?
Now I'm extremely curious, I'd like to suggest that we need a video on this lava that can no longer erupt on earth. If you don't already have one posted to RU-vid, that is. If you've already made one, if I find it I'll share it as a reply to my comment. I'm pretty busy, so if someone beats me to it, then by all means. Lol 🙂
He did a video on it before ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-E8YeGy5Ak8k.html It was a higher temperature lava type than basalt as in contained stuff that has already precipitated out of basalt. The most fascinating thing about it is its low viscosity which made it flow more like water than modern lavas
I live near the canadian shield border and found a crystal in the middle of a rock that both have some pretty cool features. A geophysisist (not sure how to spell that my bad) looked at it and said it is called an Augen Gniess and formed about 1.5 billion years ago by sheer tectonics movement. The crystal inside the middle can be almost any hard crystal. I beleive it is a feldspar type but it's hard to tell. But it has rainbow shiller effect lines, which i found spectacular, otherwise the crystal looks like a dull greyish colour. I tried extracting the crystal but had no luck as the surrounding rock is very hard and full of different types of crystal much like granite that has been fused together to be even harder. Augen is the german word for eye, because the feldspar on the outer portions of rock have been melted slightly and stretched giving them the look of a half closed human eye. 😁💖 i love canadian geology
I live in northern Saskatchewan Canada. It is bedrock and part of the Canadian Shield as you call it. This is the first time I have heard the term Canadian Shield and have always known it as the Precambrian Shield. Have I been wrong all this time or are they one in the same?
As an Ontarian I've known the term for most of my life but usually just call it the shield anyways. Your case is probably just what the locals call it rather than the scientific term
Actually, this may explain why all the border lakes around the Minnesota Arrowhead all seem to run East-West. (They were the border routes for the fur trapping trade...) I've canoed a few in the Boundary Waters... Can you explain why all these border lakes run East-West? Was it cracking around the edges of the Canadian Shield?
Why does Canada, Alaska and even some areas in Russia all have what seem to be thousands of small lakes all running the same sort of direction? Are they ancient markings of ice sheets? Or just simple tectonics?
On the Canadian Shield, in the province of Quebec, the west side in the Hudson Bay looks like an extremely large crater, which I know isn't quite the case, but why does the area have such a round looking edge to it
I haven't looked it up; but I'm guessing those other lakes aren't very deep and in general more narrow/stringy, so by sheer water capacity they probably don't even compare.
The elephant in the room (and seldom discussed) are the periodic pole shifts that occur throughout earth history. It’s been suggested that a previous pole shift (concurrent with a earth crustal displacement) moved Hudson Bay from its position as the former North Pole, to its present location. This accounts for it being the center of the Laurentide Ice Sheet during the Last Glacial Maximum (LGM). Would this account for massive ice coverage over North America - as compared to ice coverage in Eastern Asia ?
Lake Athabasca is on 2 significant unconformities. The unconformity of the crystalline basement rocks of more typical Canadian Shield on the north shore and the 1.5 billion unmetamorphosed sandstone of the Athabasca Basin. Also the unconformity of the shield and the Western Interior Seaway sediments. You can see the sand dunes from the erosion of the sandstone on the south shore of Lake Athabasca. They are the northern most active sand dunes. The Athabasca Basin is by far my favourite part of the shield, it is unique for many reasons.
Hudson Bay was the most depressed part of where the ice sheet was. It compressed so much that it is below sea level. It is shield underneath all the marine sediments for sure though.
Lakes and ponds occur along rivers, streams and brooks in lowland areas. They are not really in a straight line, they are close enough together you could draw a line through them though.
I think a good topic for a future video would be about the US Great Lakes. I was watching something one time where it said I think Superior has basalt in it which means there has been some lava present in there at one time.
Yeah the great lakes of North America are ancient rift lakes associated with an extensive failed Mesoproterozoic rift complex. They had for most of the planets history become filled in by sedimentation and eventually sedimentary rocks but during the Pleistocene they were once again excavated by glaciers as the less resistant sedimentary rock layers were carved away.
Look up the "Mid Continental Rift in North America." Apparently, it was so large (It extended all the way into Kansas) it almost ripped (what was to become) North American in two. If @Geologyhub hasn't done a video on it, he should...
There is some cool geology in the upper midwest from glaciers. If you guys like this kind of stuff, search for geologic points of interest near where you live. There is always something that will surprise you. Email a professor nearby, and I bet they could give the best list. Then get outside, see some geology, and enjoy the world. You don’t have to go to school forever to be an enthusiast in ANY science field.
