Dr. David Gwynn

globally, as well as in North America, this was also the time when sea levels were at their lowest worldwide. And we know why that is. If you're building a glacier over North America, and at the same time building one over Northern Europe, the so-called Fenoscandian ice sheet, basically what you're doing is you're interrupting the hydrological cycle.

globally, as well as in North America, this was also the time when sea levels were at their lowest worldwide. And we know why that is. If you're building a glacier over North America, and at the same time building one over Northern Europe, the so-called Fenoscandian ice sheet, basically what you're doing is you're interrupting the hydrological cycle.

globally, as well as in North America, this was also the time when sea levels were at their lowest worldwide. And we know why that is. If you're building a glacier over North America, and at the same time building one over Northern Europe, the so-called Fenoscandian ice sheet, basically what you're doing is you're interrupting the hydrological cycle.

The hydrological cycle, just put it in very simplistic terms, you've got evaporation from the ocean, clouds move over the land, they rain, the water drains into rivers, it goes back into the ocean. Okay? Real simple. Well, simplistic actually, but for our purposes, that'll work, right? If you stop that water by freezing it on land, it doesn't get back into the ocean. What happens?

The hydrological cycle, just put it in very simplistic terms, you've got evaporation from the ocean, clouds move over the land, they rain, the water drains into rivers, it goes back into the ocean. Okay? Real simple. Well, simplistic actually, but for our purposes, that'll work, right? If you stop that water by freezing it on land, it doesn't get back into the ocean. What happens?

The hydrological cycle, just put it in very simplistic terms, you've got evaporation from the ocean, clouds move over the land, they rain, the water drains into rivers, it goes back into the ocean. Okay? Real simple. Well, simplistic actually, but for our purposes, that'll work, right? If you stop that water by freezing it on land, it doesn't get back into the ocean. What happens?

Ocean levels go down. And the amount that they've gone down is going to vary geographically. because of a bunch of things that are related to gravitational forces, the pull of an ice sheet, continental shelves, mass. But on average, it's going to be about 130 meters lower than it is today, okay?

Ocean levels go down. And the amount that they've gone down is going to vary geographically. because of a bunch of things that are related to gravitational forces, the pull of an ice sheet, continental shelves, mass. But on average, it's going to be about 130 meters lower than it is today, okay?

Ocean levels go down. And the amount that they've gone down is going to vary geographically. because of a bunch of things that are related to gravitational forces, the pull of an ice sheet, continental shelves, mass. But on average, it's going to be about 130 meters lower than it is today, okay?

What that does, of course, is it exposes shallow continental shelf, continental margins, and those become land, right? areas that are now underwater or land. And that includes, of course, the continental shelf that lies underneath the Bering Sea. So that's northwest? Indeed, indeed. That's Alaska area. It's only, you know, if you go out to the Bering Sea today, it's only about 52 meters.

What that does, of course, is it exposes shallow continental shelf, continental margins, and those become land, right? areas that are now underwater or land. And that includes, of course, the continental shelf that lies underneath the Bering Sea. So that's northwest? Indeed, indeed. That's Alaska area. It's only, you know, if you go out to the Bering Sea today, it's only about 52 meters.

What that does, of course, is it exposes shallow continental shelf, continental margins, and those become land, right? areas that are now underwater or land. And that includes, of course, the continental shelf that lies underneath the Bering Sea. So that's northwest? Indeed, indeed. That's Alaska area. It's only, you know, if you go out to the Bering Sea today, it's only about 52 meters.

That sea level is about 52 meters above what's the continental shelf below it. So all you have to do is drop sea level 52 meters and you can walk from Asia to To America. You can walk from Siberia to Alaska, okay? All right.

That sea level is about 52 meters above what's the continental shelf below it. So all you have to do is drop sea level 52 meters and you can walk from Asia to To America. You can walk from Siberia to Alaska, okay? All right.

That sea level is about 52 meters above what's the continental shelf below it. So all you have to do is drop sea level 52 meters and you can walk from Asia to To America. You can walk from Siberia to Alaska, okay? All right.

So we assume, and there's no reason to doubt, that the way in which humans got here, and in fact, the way in which animals over time may have come to the Americas, is that during these episodes where you have a lot of ice on land, there were these bridges, these land bridges. And so people came across. But at the same time, let me just give you a quick... geography of the ice sheets themselves.

So we assume, and there's no reason to doubt, that the way in which humans got here, and in fact, the way in which animals over time may have come to the Americas, is that during these episodes where you have a lot of ice on land, there were these bridges, these land bridges. And so people came across. But at the same time, let me just give you a quick... geography of the ice sheets themselves.

So we assume, and there's no reason to doubt, that the way in which humans got here, and in fact, the way in which animals over time may have come to the Americas, is that during these episodes where you have a lot of ice on land, there were these bridges, these land bridges. And so people came across. But at the same time, let me just give you a quick... geography of the ice sheets themselves.

There's two major ice sheets in North America. There's the Laurentide ice sheet, which extends from what's present-day northern North America down to Central Ohio. I don't know if that's going to work for all of your audience, but basically past the Canadian-US border. Yes.

There's two major ice sheets in North America. There's the Laurentide ice sheet, which extends from what's present-day northern North America down to Central Ohio. I don't know if that's going to work for all of your audience, but basically past the Canadian-US border. Yes.