Wednesday, January 16, 2008

Change is Normal

The BBC website has yet another of those chilling reports about climate change. Our coastlines are eroding faster because of climate change.

This really is another example of short term short-sighted science. We are still experiencing the major climate change as the planet warms up after the last of the four Ice Ages. Our coastlines are, in fact, highly unstable because of this major warming period and have been for over 10,000 years. Visit many of the shale and mudstone cliffs along the south coast of England and you should marvel that there are cliffs there at all. Barton-on-Sea has steep, fast eroding cliffs made of a plastic grey mud (not even a mudstone) that is continually slumping into the sea. Lyme Regis is famous for its Blue Lias shales that are also sliding seaward, carrying and exposing beautiful ammonite fossils with them. The red Triassic marls around Sidmouth are also collapsing as has been documented on this blog.

The reason why we have such soft cliff coastlines is simple. The last ice age captured a lot of water in the ice sheets, causing a lowering of global sea levels. Then, when the ice began to melt, the oceans migrated back onto the land and began a rapid phase of erosion. Atypically fast erosion, I should stress. Although geologists often refer to the Principle of Uniformitarianism (which states that the Present is the Key to the Past) we do know that this rule was made to be broken. And the sight of mudstone cliffs 500 feet high make the point rather well!

In the long term we can assume that erosion is gradually slowing down along the UK's coasts as equilibrium is attained. Not that we are close to equilibrium yet, in fact it may never be reached if we are plunged into another ice age within the next 15,000 years.