The work of the sea

The work of the sea is focused at the coastline, probably the most active and diverse of Earth’s geomorphological features, found in every tectonic and climatic setting. It stretches for 0·5 M km around the margins of every continent and island – ten times farther than intra-plate boundaries – and is familiar to most people. Indeed, 50 per cent of the population of the industrialized world and perhaps 60 per cent of all people live within 50 km of the sea. The narrow coastal zone occupies less than 0·05 per cent of Earth’s land area but has powerful attractions for agriculture, industry, transport, residence and recreation. Consequently, we want it to stay where it is! Most of us were unwitting geomorphologists in our youth as we built sandcastles, doomed by the tide. We also recall Cnut (Canute), the Anglo-Danish king of England in the early eleventh century, and his legendary demonstration that even regal power cannot withstand the relentless motion of tides and waves. The coastline is sensitive to rapid geological and biophysical change and we are braced to respond to sea-level rise promoted by global warming.