Sea ice on the Hudson Bay breaks up and slowly recedes as the warmer temperatures of spring and summer make their way north into Quebec Province in eastern Canada, shown here in this true-color Terra MODIS image from May 21, 2005. Hudson Bay, and the smaller James Bay that protrudes south between Ontario and Quebec provinces in the lower part of the image, freezes over every winter and remains impassible to all but the strongest of ice-breaking ships for a good portion of the year. Both are actually a vast inland sea connected to both the Atlantic and Arctic oceans.
The Hudson Bay occupies the southernmost portion a depression in the land that was created by the weight of a continental ice sheet in the Pleistocene epoch (between 1.8 million and 11,000 years ago). As the ice sheet retreated, the depression was filled with sea water and sediments. With the weight of the ice sheet now gone, the floor of the compressed Bay is slowly rising, and both the Hudson Bay and James Bay are gradually becoming shallower.
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