Isostatic rebound

Prince of Wales Fort National Historic Site

For many years, it was thought that the dry cove was a result of the phenomenon known as isostatic rebound. This situation describes the gradual rising of land elevations as it springs back after thousands of years of being crushed under the weight of continental glaciers. The west coast of Hudson Bay is known as one of the more dramatic areas of isostatic rebound where the land still rises at a rate of a metre per century. This is especially noticeable in the flat lowland areas of the coast. However, at Sloop Cove, mooring ships in 1750 would have involved a situation where the daily water level was, at most, less than 3 m higher than today. This situation would have resulted in a large pool in the cove where the Centre was about 1 m deep and most of the pool was 50 centimetres or less - hardly enough for boat mooring. However, even at an increase of only 2 m, the cove becomes an almost perfect dry dock. At high tide, there is enough water to easily drag the boat into the mouth of the cove and past the breakwater and natural island. Then the boat can be manhandled through a shallow, salt water pond to the location desired. Once into the cove, there is little chance of damage from ice or storms.

A map of Sloop Cove near Prince of Wales Historic Site. The map compares current and historic water levels.
Sloop Cove water levels
© Parks Canada/ PWF Collection
Image description
A map features an inlet of water in the middle with land at the top and bottom of the image. In the centre of the inlet is a green section identified by the legend as a modern pond. It is surrounded by a teal section indicating the land is 3 metres above former levels. To the right, there’s a light blue section indicating the level is 2 metres, with an indigo section to the right of that indicating the level is 1 metre, and a dark blue section at the right edge of the map indicating current levels. The legend also indicates that red dots denote pin locations.

Above, a recently constructed contour map has been used to help picture what the cove would have looked like at various times in the past. Notice that, at 3 m, the breakwater along the east edge was virtually totally underwater. As this is a man made feature, it is likely that it was constructed to the edge of the water. The 2 m line appears to be a more reasonable level. That level would also show the island as a decent sized outcrop, not just a piece of rock surfacing out of the water.

Date modified :