Assessing whether extreme tidal and wave currents can erode bedrock

What is it about?

Tidal currents are usually too weak to remove particles from bedrock. This article assesses whether tidal currents can reach speeds sufficient to remove bedrock particles, such as where enhanced by waves. We use data from high-resolution sonars to study the morphologies of rock outcrops in areas of unusually strong tidal streams, such as in the Minas Passage of the Bay of Fundy, off South Wales, UK, and in the Strait of Messina, Italy. Current speeds were assessed from a variety data from current meters and other sources. The results suggest that tidal currents can approach or perhaps occasionally exceed the thresholds needed for eroding bedrock in isolated cases.

Featured Image

Photo by Alex Rhee on Unsplash

Photo by Alex Rhee on Unsplash

Why is it important?

Tidal height variations have been predicted to have been greater (by up to a factor of two in places) when sea level was lower during times of glacial maxima, a result of reduced attenuation of tidal wave currents by friction on Earth's continental shelves, then greatly reduced by lower sea level. Given greater tidal height providing greater potential energy for currents, this implies that there may have been areas in the past when tidal currents were stronger and therefore actually caused bedrock erosion.