<p>It is thought that they were carved by ice rivers, particularly Superior, during the last ice age. Ice rivers are basically glaciers that are very fast moving which means they're far from the <a href="https://polarpedia.eu/en/equilibrium-line-altitude-ela/" rel="noreferrer">equilibrium altitude</a> of their current climate. If you have a look at a projected ice map for the Americas c.7000BC you'll see that where the great lakes now sit was close to, if not the actual at, the southern edge of the North American ice cap.</p>

CC BY-SA 4.0
2024-08-28T08:10:54.963Z
I think I'm missing why the ice rivers would stop along the same line, especially if it's away from the equilibrium altitude.
Rad80
CC BY-SA 4.0
2024-08-28T08:27:03.073Z
@Rad80 Equilibrium altitude rises the closer you are to the equator, I vaguely recall it being something like 5m per km but check that, don't quote me on it, my Glaciers and Glaciation lectures were a *long* time ago. The ice caps physical altitude didn't change to shift it away from equilibrium, it's latitude did. The ice rivers carving the great lakes all dropped below equilibrium at the same latitude and started their rapid erosion phase. They stop along the same line because that's where the ice finishes melting.
Ash
CC BY-SA 4.0
2024-08-27T10:45:24.767Z
2024-08-27T10:45:24.767Z
Ash
<p>I noticed that the biggest lakes in North America (which happen to all be in Canada) seem to lie along a line that from the Great Bear Lake passes through the Great Slave Lake, Lake Athabasca and Lake Winnipeg (among others) to Lake Superior and the rest of the Great Lakes.
This is particularly evident in a Mercator projection map where the line is practically straight, at least until the Great Lakes are reached.</p>
<p>I thought there might be a rift but it looks like that's not the case and seismic hazard maps for Canada don't show anything remarkable about the area.</p>
<p>Is there a reason for all those big lakes to be aligned in this way?</p>

CC BY-SA 4.0
2024-08-27T10:32:13.163Z
The first three you cite were once a single lake: https://en.wikipedia.org/wiki/Lake_McConnell
But the two groups being seemingly aligned is probably just a coincidence.
Jean-Marie Prival
CC BY-SA 4.0
2024-08-28T14:00:20.010Z
Related: Why are most big mountain ranges in North America aligned? ;-)
Peter - Reinstate Monica
<geography><lakes><canada>
Why are most big lakes in North America aligned?
Rad80
# Why are most big lakes in North America aligned?

(Asked by: username_0 on 2024-08-27)

I noticed that the biggest lakes in North America (which happen to all be in Canada) seem to lie along a line that from the Great Bear Lake passes through the Great Slave Lake, Lake Athabasca and Lake Winnipeg (among others) to Lake Superior and the rest of the Great Lakes.
This is particularly evident in a Mercator projection map where the line is practically straight, at least until the Great Lakes are reached.

I thought there might be a rift but it looks like that's not the case and seismic hazard maps for Canada don't show anything remarkable about the area.

Is there a reason for all those big lakes to be aligned in this way?

**Tags:** geography, lakes, canada

> **Comments:**
> **username_1**: The first three you cite were once a single lake: https://en.wikipedia.org/wiki/Lake_McConnell But the two groups being seemingly aligned is probably just a coincidence.  
> **username_2**: Related: Why are most big mountain ranges in North America aligned? ;-)  

---

## 1 answers

### Answer by username_3 on 2024-08-27. Score: 8

It is thought that they were carved by ice rivers, particularly Superior, during the last ice age. Ice rivers are basically glaciers that are very fast moving which means they're far from the [equilibrium altitude](https://polarpedia.eu/en/equilibrium-line-altitude-ela/) of their current climate. If you have a look at a projected ice map for the Americas c.7000BC you'll see that where the great lakes now sit was close to, if not the actual at, the southern edge of the North American ice cap.

> **Comments:**
> **username_0**: I think I'm missing why the ice rivers would stop along the same line, especially if it's away from the equilibrium altitude.  
> **username_3**: @username_0 Equilibrium altitude rises the closer you are to the equator, I vaguely recall it being something like 5m per km but check that, don't quote me on it, my Glaciers and Glaciation lectures were a *long* time ago. The ice caps physical altitude didn't change to shift it away from equilibrium, it's latitude did. The ice rivers carving the great lakes all dropped below equilibrium at the same latitude and started their rapid erosion phase. They stop along the same line because that's where the ice finishes melting.  

---

