Giants Causeway

Giant's Causeway, a remarkable mass of doleritic or coarsely-crystalline basalt (q.v.) in county Antrim, on the north-east coast of Ireland. It consists of horizontal flows, so that the columns of the basalt, which are at right-angles to the surface of cooling, stand vertically. They are jointed horizontally, and have thus been eroded by weather and sea into a series of terraces and steps strikingly resembling a piece of Cyclopean masonry. The geological age of the basalts of this region, as indicated by leaf-beds between the lava-flows, seems to extend from the close of the Cretaceous period to the Miocene. Those of Staffa, Mull, and Skye, and some of those of Iceland, are of the same ages.