Queen Charlotte Shelf

 

The steep Queen Charlotte shelf helps to decrease the height of the tides around the island

Tidal ranges and patterns vary along the coast. Over most of the world’s coastal regions, the difference between water levels at high and low tide - the tidal amplitude or range - averages 2 metres. The tides along the Pacific coast range in amplitude from 2.5 metres to about 4 metres. In the northern region of the coast, off the Queen Charlotte Islands, the shelf is steep relative to the other shelves of the Pacific region. This steep shelf limits the amplitude of the tides to 2 metres. When tides run into deep continental shelves, their rate of movement is increased due to the lack of friction along the shore. This results in an even dispersal of energy as the water rushes in, and a smaller tidal amplitude than in shallower areas where the energy is concentrated into a smaller volume. However, to the east of the Queen Charlotte Islands lies the Hectate Strait, bordering the British Columbia mainland, which is considerably shallower than the shelf to the west of the islands. Therefore, in this region the tidal range is around 3-5 metres. These high tides create whirlpools and turbulent waters that have generated the complex and rugged ocean floor and coastline in this region.