How did geography change?

Sea-level curves for specific areas are interesting in themselves, but there is a better way to illustrate regional changes in changing sea level. There are three steps in the process.

First we make maps showing the former sea levels at different times (isobase maps). Here is the situation 10,000 years before present. Sea level is lower than now on the continental shelf, but is ABOVE the modern level in northern Newfoundland, Labrador, and Quebec (along the red line, sea level is exactly at the modern level).

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Second, we make a digital terrain model of the region, both land and sea. In the final step we subtract the isobase values from the digital terrain model, to derive the paleogeography.

The continental shelf around Atlantic Canada is distinctive for many reasons, including:

1. the Laurentian Channel, overdeepened by ice streams during the ice age;
2. the sharp break that marks the edge of the continental shelf; and
3. the shallow banks separated from the coast by deep water.

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