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> In this climate change age The Great Lakes only exist because the massive ice sheet melted and left the lakes as a deposit some 10-15,000 years ago. I would

> In this climate change age The Great Lakes only exist because the massive ice sheet melted and left the lakes as a deposit some 10-15,000 years ago. I wouldn’t be surprised if in a few thousand years the lakes largely dissipate. That said I grew up near the lake, definitely something that’s awesome to live near

cmrdporcupine 5y ago
A few thousand years is a long time. The lakes will be an essential treasure for the next 200 tumultuous years when water supplies become difficult. Imagine what it was like here when the ice sheets first retreated. Niagara falls but times 100.
khuey 5y ago
The Great Lakes will eventually go away, but not for the reason you think. Niagara Falls is eroding its way upstream and will eventually reach Lake Erie, at which point Lakes Erie, Huron, and Michigan will all drain away downstream.
- bregma 5y ago
  How would that work. Would the Niagara gorge suddenly be able to increase its capacity orders of magnitude beyond its physical limits? Would the Detroit and St. Clair rivers suddenly be able to deliver an increased flow into Eerie?
  - jblindsay 5y ago
    Yes, that's correct, it would increase its capacity by orders of magnitude, if not temporarily. The capacity of Lake Erie to hold water is set by the elevation of its outlet, which is currently about 174 m above sea level. Niagara Falls is a knickpoint in the Niagara river, and over time knickpoints in rivers are always smoothed out. This is why Niagara Falls is eroding upstream, and we spend money each year trying to minimize this. As it works it way upstream, it will eventually intersect with the outlet of Lake Erie (over geological time scales), and will start to erode the outlet elevation downwards to achieve that nice concave-upwards longitudinal profile indicative of a river in dynamic equilibrium. In doing so, it will reduce the capacity of Lake Erie quite significantly. Someone above stated that the Great Lakes are below sea-level, and that's true for parts of most of the lakes, but not Erie, which has a maximum depth of about 64 m. It will eventually, over the long term become a wide part of the long river connecting Huron and Ontario. By the way, there are plenty of precedents for rivers suddenly and temporarily increasing their capacity to handle a sudden increase in flow; Google 'channelled scablands' and you might be surprised. I often joke with students that I won't want to live in Missisauga on the shores of Lake Ontario, which I do currently, when this event happens. Of course, it's only a joke because we're talking about a very, very long time away. As for the Detroit and St. Claire rivers increasing their capacity to Erie, I'm not sure why that would be necessary. Flow through this newly created 'Erie River' would simply adapt to carry the capacity of water supplied by Huron all the way to Lake Ontario, just as the Niagara river does now. There's no need for upstream change. Just think, the St. Lawrence River has the ability to convey the entire water supplied by all of the Great Lakes to the Atlantic.
    - Kon-Peki 5y ago
      Perhaps the missing component in understanding this is the time frame for draining Huron/Michigan into "River Erie". So Niagara is slowly eroding and will eventually reach a tipping point where further erosion will increase the rate of outflow from Erie. The increased outflow will increase the rate of erosion which will increase the rate of outflow, and so on. Correct? When this is happening, the rate of outflow from Michigan/Huron via Detroit and St Claire will increase, but erosion is not necessary for this to occur? Say we built a dam on the Detroit River that keeps Michigan/Huron at its current water level. And then Erie turns into a river. Once that transition is complete, we destroy the dam. How much time is necessary for Michigan/Huron to drain? Is the timescale days, weeks, months, years, etc?
      - jblindsay 5y ago
        To be clear, I'm not saying that the draining of Lake Erie necessarily means that Lake Huron/Michigan or Superior would drain too. If that were to happen, the two events would be quite separate and likely separated by millennia. Lake Erie's water level will lower when/if the Niagara river erodes all the way back to to the outlet of Lake Erie, and Lake Erie will become a river, when it erodes all the way to the middle of the lake (actually the deepest part). Obviously, this event, should it happen at all, would be thousands if not hundreds of thousands of years from now, assuming that climate doesn't change such that the Great Lakes dry up, or that there isn't further geological activity/uplift. Would this draining of Erie result in a catastrophic flood when it does happen? I don't know, I suppose it depends on the erodability and topographic character of the outlet area at the time. But it is surely the case that the draining of Erie (i.e. the reduction in its capacity to store water) would result in an immediate but temporary increase in the flow through the Niagara river, as it conveys the regular flow from the upper Great Lakes as well as the additional storage loss of Erie. Once the river eroded to the deepest part of Erie, however, flow would resume to simply be controlled by the water delivered to the river by Huron. Would the river continue to erode to the outlet of Huron and result in a similar draining of the upper Great Lakes? I don't know, but I do know that would be over extensive geological time scales and that there is plenty of opportunity for climate change to have a great impact on this possible scenario--Erie draining is much more immediate by comparison. However, something that many Canadians like myself don't often realize, because we live in the country with the greatest number of lakes, is that lakes are generally not that common worldwide. They represent temporary landscape features that are reflective of a relatively recent (in geological terms) disturbance...in the case of most of Canada's lakes, a recent glaciation. Lakes eventually drain as their outlets are eroded down and fill in by sediment delivery from upstream. And the same will likely be true of all of the Great Lakes over a long enough time. There is nothing permanent about our landscapes and that's exactly what makes Earth so awesome as a planet. It's dynamic and varied and today's 'great' lakes can be tomorrow's dry desert plains. We may well be devastating this planet, and its ecosystems specifically, but in the long-view, we'll likely be nothing more than a blip in the history of Earth, and one that it will erase most evidence of after enough time. I don't know why, but there is something reassuring about that thought to me.
- gilbetron 5y ago
  That will just make Lake Erie and Lake Ontario merge, more or less. Why would it drain Michigan at all? This is old, but it's also possible that niagara falls just stops being falls and stops moving upstream: https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/85/1/91/201572/What-Future-for-Niagara-Falls?redirectedFrom=fulltext https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abs...
- phkahler 5y ago
  >> Niagara Falls is eroding its way upstream and will eventually reach Lake Erie, at which point Lakes Erie, Huron, and Michigan will all drain away downstream. The Detroit river, lake StClair, and the StClair river beg to differ. In particular, StClair has a channel cut through it for shipping to be possible as much of it is less than 10 feet deep. Flow would increase, but I think they'd maybe add a dam and lock somewhere to stop it. But Niagara is a long way from that point, especially since diversion for power has dramatically slowed the erosion.
- fredsmith219 5y ago
  I live on the Huron River in southeast Michigan and like to tease my son that in a few thousand years we will have the falls in our back yard. He is somewhat skeptical but loves the idea.
throwaway894345 5y ago
If this is true ("only b/c of melting ice sheet; will dissipate in next few thousand years") then wouldn't we expect water levels to be continuously dropping? Seems more likely that they exist because rain/meltwater makes its way to the basin and keeps them filled (irrespective of whether or not they were originally filled with meltwater from the ice sheet 15kya).
- cmrdporcupine 5y ago
  I believe a lot of it is ultimately fed by hundreds of thousands of square kilometers of smaller lakes upstream. The Canadian Shield is dotted with gazillions of lakes, it's crazy to fly over it. And I think it's safe to assume most of those lakes are glacial remnant water, not sure if they're fully refreshed by rain and snow.
  - throwaway894345 5y ago
    Then I would expect these upstream lakes to be shrinking as of the last 10-15kya.
  - bregma 5y ago
    I know it's the internet and facts are as real as birds, but just in case you want some: [0]. [0] https://www.lre.usace.army.mil/Missions/Great-Lakes-Information/Great-Lakes-Information-2/Basin-Conditions/ https://www.lre.usace.army.mil/Missions/Great-Lakes-Informat...
    - garbagetime 5y ago
      That's a pretty unecsscesary footnote
  - maxerickson 5y ago
    The watershed(s) aren't crazy huge: https://project.geo.msu.edu/geogmich/watershed.html https://project.geo.msu.edu/geogmich/watershed.html (Like just as a gut check, much of the border of Wisconsin and Minnesota is a tributary of the Mississippi River)
bregma 5y ago
The depths of all the lakes except Eerie are below mean sea level. It would require a prolonged period of new orogeny for the lakes to disappear. Since that hasn't happened in a few billion years in the area, it's more likely that the sun will expand to encompass the orbit of the Earth and vapourize the entire planet first. Hardly something that will happen in a few thousand years. But you never know.
zamadatix 5y ago
Superior was around a lot longer than that. Regardless based on the extreme water height swings since the glacial retreat water level seems to now depend more on climate and what the outlets are doing than anything to do with the melt off from the last glacial period. With humans already having much to do with both of these what will happen to them in the long run seems strictly up to our choices.

cmrdporcupine 5y ago

A few thousand years is a long time. The lakes will be an essential treasure for the next 200 tumultuous years when water supplies become difficult. Imagine what it was like here when the ice sheets first retreated. Niagara falls but times 100.

khuey 5y ago

The Great Lakes will eventually go away, but not for the reason you think. Niagara Falls is eroding its way upstream and will eventually reach Lake Erie, at which point Lakes Erie, Huron, and Michigan will all drain away downstream.

bregma 5y ago
How would that work. Would the Niagara gorge suddenly be able to increase its capacity orders of magnitude beyond its physical limits? Would the Detroit and St. Clair rivers suddenly be able to deliver an increased flow into Eerie?
- jblindsay 5y ago
  Yes, that's correct, it would increase its capacity by orders of magnitude, if not temporarily. The capacity of Lake Erie to hold water is set by the elevation of its outlet, which is currently about 174 m above sea level. Niagara Falls is a knickpoint in the Niagara river, and over time knickpoints in rivers are always smoothed out. This is why Niagara Falls is eroding upstream, and we spend money each year trying to minimize this. As it works it way upstream, it will eventually intersect with the outlet of Lake Erie (over geological time scales), and will start to erode the outlet elevation downwards to achieve that nice concave-upwards longitudinal profile indicative of a river in dynamic equilibrium. In doing so, it will reduce the capacity of Lake Erie quite significantly. Someone above stated that the Great Lakes are below sea-level, and that's true for parts of most of the lakes, but not Erie, which has a maximum depth of about 64 m. It will eventually, over the long term become a wide part of the long river connecting Huron and Ontario. By the way, there are plenty of precedents for rivers suddenly and temporarily increasing their capacity to handle a sudden increase in flow; Google 'channelled scablands' and you might be surprised. I often joke with students that I won't want to live in Missisauga on the shores of Lake Ontario, which I do currently, when this event happens. Of course, it's only a joke because we're talking about a very, very long time away. As for the Detroit and St. Claire rivers increasing their capacity to Erie, I'm not sure why that would be necessary. Flow through this newly created 'Erie River' would simply adapt to carry the capacity of water supplied by Huron all the way to Lake Ontario, just as the Niagara river does now. There's no need for upstream change. Just think, the St. Lawrence River has the ability to convey the entire water supplied by all of the Great Lakes to the Atlantic.
  - Kon-Peki 5y ago
    Perhaps the missing component in understanding this is the time frame for draining Huron/Michigan into "River Erie". So Niagara is slowly eroding and will eventually reach a tipping point where further erosion will increase the rate of outflow from Erie. The increased outflow will increase the rate of erosion which will increase the rate of outflow, and so on. Correct? When this is happening, the rate of outflow from Michigan/Huron via Detroit and St Claire will increase, but erosion is not necessary for this to occur? Say we built a dam on the Detroit River that keeps Michigan/Huron at its current water level. And then Erie turns into a river. Once that transition is complete, we destroy the dam. How much time is necessary for Michigan/Huron to drain? Is the timescale days, weeks, months, years, etc?
    - jblindsay 5y ago
      To be clear, I'm not saying that the draining of Lake Erie necessarily means that Lake Huron/Michigan or Superior would drain too. If that were to happen, the two events would be quite separate and likely separated by millennia. Lake Erie's water level will lower when/if the Niagara river erodes all the way back to to the outlet of Lake Erie, and Lake Erie will become a river, when it erodes all the way to the middle of the lake (actually the deepest part). Obviously, this event, should it happen at all, would be thousands if not hundreds of thousands of years from now, assuming that climate doesn't change such that the Great Lakes dry up, or that there isn't further geological activity/uplift. Would this draining of Erie result in a catastrophic flood when it does happen? I don't know, I suppose it depends on the erodability and topographic character of the outlet area at the time. But it is surely the case that the draining of Erie (i.e. the reduction in its capacity to store water) would result in an immediate but temporary increase in the flow through the Niagara river, as it conveys the regular flow from the upper Great Lakes as well as the additional storage loss of Erie. Once the river eroded to the deepest part of Erie, however, flow would resume to simply be controlled by the water delivered to the river by Huron. Would the river continue to erode to the outlet of Huron and result in a similar draining of the upper Great Lakes? I don't know, but I do know that would be over extensive geological time scales and that there is plenty of opportunity for climate change to have a great impact on this possible scenario--Erie draining is much more immediate by comparison. However, something that many Canadians like myself don't often realize, because we live in the country with the greatest number of lakes, is that lakes are generally not that common worldwide. They represent temporary landscape features that are reflective of a relatively recent (in geological terms) disturbance...in the case of most of Canada's lakes, a recent glaciation. Lakes eventually drain as their outlets are eroded down and fill in by sediment delivery from upstream. And the same will likely be true of all of the Great Lakes over a long enough time. There is nothing permanent about our landscapes and that's exactly what makes Earth so awesome as a planet. It's dynamic and varied and today's 'great' lakes can be tomorrow's dry desert plains. We may well be devastating this planet, and its ecosystems specifically, but in the long-view, we'll likely be nothing more than a blip in the history of Earth, and one that it will erase most evidence of after enough time. I don't know why, but there is something reassuring about that thought to me.
gilbetron 5y ago
That will just make Lake Erie and Lake Ontario merge, more or less. Why would it drain Michigan at all? This is old, but it's also possible that niagara falls just stops being falls and stops moving upstream: https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/85/1/91/201572/What-Future-for-Niagara-Falls?redirectedFrom=fulltext https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abs...
phkahler 5y ago
>> Niagara Falls is eroding its way upstream and will eventually reach Lake Erie, at which point Lakes Erie, Huron, and Michigan will all drain away downstream. The Detroit river, lake StClair, and the StClair river beg to differ. In particular, StClair has a channel cut through it for shipping to be possible as much of it is less than 10 feet deep. Flow would increase, but I think they'd maybe add a dam and lock somewhere to stop it. But Niagara is a long way from that point, especially since diversion for power has dramatically slowed the erosion.
fredsmith219 5y ago
I live on the Huron River in southeast Michigan and like to tease my son that in a few thousand years we will have the falls in our back yard. He is somewhat skeptical but loves the idea.

throwaway894345 5y ago

If this is true ("only b/c of melting ice sheet; will dissipate in next few thousand years") then wouldn't we expect water levels to be continuously dropping? Seems more likely that they exist because rain/meltwater makes its way to the basin and keeps them filled (irrespective of whether or not they were originally filled with meltwater from the ice sheet 15kya).

cmrdporcupine 5y ago
I believe a lot of it is ultimately fed by hundreds of thousands of square kilometers of smaller lakes upstream. The Canadian Shield is dotted with gazillions of lakes, it's crazy to fly over it. And I think it's safe to assume most of those lakes are glacial remnant water, not sure if they're fully refreshed by rain and snow.
- throwaway894345 5y ago
  Then I would expect these upstream lakes to be shrinking as of the last 10-15kya.
- bregma 5y ago
  I know it's the internet and facts are as real as birds, but just in case you want some: [0]. [0] https://www.lre.usace.army.mil/Missions/Great-Lakes-Information/Great-Lakes-Information-2/Basin-Conditions/ https://www.lre.usace.army.mil/Missions/Great-Lakes-Informat...
  - garbagetime 5y ago
    That's a pretty unecsscesary footnote
- maxerickson 5y ago
  The watershed(s) aren't crazy huge: https://project.geo.msu.edu/geogmich/watershed.html https://project.geo.msu.edu/geogmich/watershed.html (Like just as a gut check, much of the border of Wisconsin and Minnesota is a tributary of the Mississippi River)

bregma 5y ago

The depths of all the lakes except Eerie are below mean sea level. It would require a prolonged period of new orogeny for the lakes to disappear. Since that hasn't happened in a few billion years in the area, it's more likely that the sun will expand to encompass the orbit of the Earth and vapourize the entire planet first. Hardly something that will happen in a few thousand years. But you never know.

zamadatix 5y ago

Superior was around a lot longer than that. Regardless based on the extreme water height swings since the glacial retreat water level seems to now depend more on climate and what the outlets are doing than anything to do with the melt off from the last glacial period. With humans already having much to do with both of these what will happen to them in the long run seems strictly up to our choices.