Everything about The Cordilleran Ice Sheet totally explained
The
Cordilleran ice sheet was a major
ice sheet that covered, during glacial periods of the
Quaternary, a large area of
North America. This included the following areas:
The ice sheet covered up to two and a half million square kilometres at the
Last Glacial Maximum and probably more than that in some previous periods such as the
Kansan Glaciation, when it may have extended into the northeast extremity of
Oregon and the Salmon River Mountains in Idaho. It is probable, though, that its
northern margin was
further south due to the influence of
starvation caused by very low levels of precipitation.
At its eastern end the Cordilleran ice sheet merged with the
Laurentide ice sheet at the
Continental Divide, forming an area of ice that contained one and a half times as much water as the
Antarctic ice sheet does today. At its western end it's believed nowadays that several small glacial refugia existed during the last glacial maximum below present
sea level in now-submerged
Hecate Strait and on the
Brooks Peninsula in northern
Vancouver Island. However, evidence of ice-free refugia
above present sea level north of the
Olympic Peninsula has been refuted by genetic and geological studies since the middle 1990s. The ice sheet faded north of the
Alaska Range because the climate was too dry to form
glaciers.
Unlike the Laurentide ice sheet, which is believed to have taken
as much as eleven thousand years to fully melt, it's believed the Cordilleran ice sheet, except for areas that remain glaciated today, melted
very quickly, probably in four thousand years or less. This rapid melting caused such
floods as the overflow of
Lake Missoula and shaped the topography of the extremely fertile
Inland Empire of
Eastern Washington.
Sea levels during glaciation
Because of the weight of the ice, the mainland of northwest North America was so depressed that sea levels at the
Last Glacial Maximum were over a hundred metres higher than they're today (measured by the level of
bedrock).
However, on the western edge at the
Queen Charlotte Islands (which, contrary to "popular" myths of ice-free
refugia, were
entirely glaciated during the LGM) the lower thickness of the ice sheet meant that sea levels were as much as
170 metres lower than they're today, forming a large
lake in the deepest parts of the strait. This was because the thickness of the centre of the ice sheet actually served to push upwards areas at the edge of the continental shelf which,
even though glaciated, were displaced and lifted by the pressing of the crust further inland. The effect of this during deglaciation was that sea levels on the edge of the ice sheet, which naturally deglaciated first, initially rose due to an increase in the volume of water, but later fell due to rebound after deglaciation.
These effects are important because they've been used to explain how migrants to North America from
Beringia were able to travel southward during the deglaciation process due purely to the exposure of submerged land between the mainland and numerous continental islands. They are also important for understanding the direction
evolution has taken since the ice retreated.
Even today, the region is notable for its rapid changes in sea level, which, however, have little effect on most of the coast due to the numerous
fjords.
Further Information
Get more info on 'Cordilleran Ice Sheet'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://cordilleran_ice_sheet.totallyexplained.com">Cordilleran Ice Sheet Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
