Showing posts with label Glacier. Show all posts
Showing posts with label Glacier. Show all posts

Posted by Chris M Saturday, June 13, 2009

Isostatic Rebound Hudson Bay



The subject of this month's Accretionary Wedge is "Let's do a time warp". Basically, what past (or future) geologic events would you like to be able to observe.

The geologic event I choose is the isostatic rebound of the Hudson Bay region. At the end of the Pleistocene and the beginning the Holocene, the massive ice sheets covering northern North America began to melt. As the weight of thousands of meters of ice over the Hudson Bay region was removed, the surface began to rise.

As the land continued to rise, new shorelines were repeatedly being formed, as the old shorelines were elevated higher. In some places, over 175 old shorelines ring the present bay level. This is equated to over 300 m over rebound in places. And it is still rising.

If I was in a space ship, watching this event unfold in a few minutes rather than thousands of year, I would see a huge mass of ice melting, followed by a quick jump of the land surface. As time would pass, the speed of the rise would slow down. On the surrounding land surface, almost bare rock surfaces, sweep clean of soil by the glaciers, would slowly become colonized by mosses and lichen. Soil would slowly begin to form, allowing shrubs and trees to gain a foot-hold. Water that would have originally laid on the nearly flat surface, would have started to cut the beginnings of stream channels.

I have reached the present. What does the future hold? The land will continue to rise, in some places still over 100 m. As the climate warms (at least in the relative future), more trees will move even more, as the rate of soil creation increases with the warmer temperatures. Lakes will fill in and drainages patterns will become less deranged.

Posted by Chris M Monday, December 22, 2008

Map Monday #5: Worldwide Glaciation


On this week's map Monday, it is back those hotbeds of early geologic research, glaciers and the Alps. Unlike the previous map that focused on glaciation in the Alps, this attempted to combine the presently known evidence of glaciation to produce a world wide map. The map includes inserts showing greater detail in the Alps, North American, and the south island of New Zealand. The largest maps are polar projections of both the north and south poles. Once again, the map is from the David Rumsey collection.

Map Information
Eisverbreitung, einst und jetzt. Polar Ansicht der Erde in Lambert's flachenrechter Azimuthal-projection . (with) Der Rhein-Gletscher nach A. Favre. (with) Der Rhone Gletscher nach A. Falsan. (with) Seen-Gebiet in Nord-Amerika nach Chamberlin und Wright. (with) Die Europaischen Alpen. (with) Iseo-Gletscher nach Stroppani. (with) Der Loisach- und Inn-Gletscher n. Penck & Bayberger. (with) Die Sudlichen Alpen (Neu-Seeland) nach J. v. Haast. Entw. v. Herm. Berghaus 1884, Ausg. 1886. Gotha: Justus Perthes (1892)

Posted by Chris M Monday, November 24, 2008

Map Monday #2: Glaciers of the Alps


One of the first important research foci of early (19th century) geology was the Alps and their associated glaciers. People like De Saussure and Agassiz were climbing around the mountains (helping to invent the sport of mountaineering) trying to understand the processes involved.

This week's map is from 1854 and illustrates features of several Alpine glaciers. Not only is the speed of the glacier shown, but also the location of moraines and erratic boulders. These features were the first evidence of ice ages in the earth's past.

Just like last week's map, this is from the David Rumsey Collection.

Illustrations of the glacier systems of the Alps and of glacial phenomena in general. From the surveys and sketches of Professor Forbes, the maps of Raymond, Weiss, Charpentier &c., by A.K. Johnston, F.R.S.E. Engraved by W. & A.K. Johnston. William Blackwood & Sons, Edinburgh & London. 1st. November 1854. (1856)