You can still see traces of the Ice Age all over North America
These places across North America are still recovering from the Ice Age, and what’s left can be seen if you look closely enough.
If there are kilometer (mile) thick ice patches on you, you might think it’s a bit heavy. Well, the earth thinks so too. During the last Ice Age, large ice sheets covered much of North America. The weight of the ice depressed the land and today it is still bouncing in many areas.
Another relic of the last ice age to visit is the (remote) Bering Land Bridge National Preserve – it retains a remnant of an ancient land bridge that once connected North America to Asia.
The post-glacial rebound and the future
Post-glacial rebound is also called isostatic rebound and is the rise of land masses after the crushing weight of the ice sheets has disappeared. Post-glacial rebound uplift effects are evident in parts of northern Eurasia, Patagonia, Antarctica, and North America.
- Laurentide Ice Sheet: Name of the North American ice sheet centered on Hudson Bay
The ice sheets that once covered much of the northern hemisphere were up to 3 kilometers thick at the glacial maximum of about 20,000 years ago. The weight of this ice caused the Earth’s crust to warp and warp (and force the viscoelastic material of the mantle to flow out). With uplift, the mantle material returns. It will take several thousand more years before an equilibrium is reached.
*’ Future: The rebound will continue for thousands more years (at least 10,000 years)
In the beginning, there was the elastic response which was much faster. Today, the slower rebound averages about 1 cm (or a third of an inch) per year.
Northern Canada and Hudson Bay
Nowhere is as extreme as much of northern Canada. Today, land in central and northern Ontario (and surrounding provinces) is increasing. The lands of northern Ontario around the shores of Hudson Bay and James Bay are rising particularly rapidly.
The fastest rate in Ontario is about 1 to 1.3 meters (or 3.4 to 4.3 feet) per hundred years. The first settlement in Canada was established in 1604 – about 400 years ago. This would mean that these lands are now 4 to 5.2 meters or 13.6 to 17.2 feet higher than they were then. The top end approaches the height of an average 2-story house.
- Fastest rate: In some parts, the pitch rebounds between 1 and 1.3 meters or 3.4 and 4.3 feet per year
- Fastest location: The land between Fort Severn, Peawanuck and Cape Henrietta Maria is the fastest rising in Ontario
Much of the rest of northern Canada is also up, albeit less dramatically (although the lower Prairie provinces and the Maritime provinces appear to be plummeting).
When the ice began to melt, the land began to rise about 15,000 years ago. 8,000 years ago, Cape Henrietta Maria (in Ontario where James Bay and Hudson Bay merge) lay more than 100 meters (300 feet) below the sea. This ancient sea was called the Tyrrell Sea – this land emerged about 7,000 years ago.
- Has begun: The rebound began about 15,000 years ago
Today, one can find a series of abandoned beaches around Hudson Bay. Its oldest and highest inland beaches developed around 7,500 years ago. At that time, the relative sea level in the bay was about 130 meters or 430 feet higher than today. These ancient beaches can be traced back to present sea level and current beaches.
- Future: Hudson’s Bay is likely to continue to shrink as new land rises
But the process did not stop and in the future beaches will form along Hudson Bay which today is covered with mudflats. Passing through Hudson Bay, go on a polar expedition!
Glacial rebound in Europe
On the side of the Nordic countries of Europe, we can observe the effects of the post-glacial rebound in much more populated areas. Much of Finland only owes its existence to the rebound, as much of it was previously sunk under the sea.
- Finland: Much of Finland was once below sea level
- Growing Finland: Finland’s current area is growing by about 7 square kilometers per year
The process continues. The Gulf of Bothnia is the large body of water separating Finland from Sweden and the land beneath this shallow sea also bounces around. It is believed that in about 2,000 years the gulf will eventually close at Kvarken.
- Gulf of Bothnia: Separates Finland and Sweden, likely to close in about 2,000 years
- Kvarken: “Type zone” classified by UNESCO to illustrate the effect of post-glacial rebound
In other places in the Nordic countries, ports (like Tornio and Pori) had to move their ports several times because they became unusable due to the rebound.
- Place names: Some place names in the Nordic countries show that they were once islands or something else
Some place names in the area reflect changes that have occurred since the rebound. Today there are inland places called “islands”https://www.thetravel.com/parts-of-north-america-ice-age-still-visible/,”skerry”https: //www.thetravel.com/parts-of-north-america-ice-age-still-visible/,”rock”https://www.thetravel.com/parts-of-north-america-ice-age- still-visible/,”dot’ and ‘ring’. An example is Oulunsalo in northern Finland means “the island of Oulujoki but is now a peninsula.
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