Examine how different rock types produce distinctive landscapes

One rock type that produces a distinctive landscape is limestone. When limestone is exposed at the surface, it is slowly chemically weathered by carbonation to form a karst landscape like that in the Burren, County Clare. It is thought that the protective soil cover in this area was removed by glacial erosion during the last ice age, exposing the limestone bedrock to carbonation.

Carbonation is a chemical weathering process that occurs when rain absorbs carbon dioxide as it falls through the atmosphere to become a weak carbonic acid.  Carbonic acid slowly dissolves limestone rock, especially in areas where the rock is exposed, but also underground.

Limestone is a jointed and layered sedimentary rock. Joints are vertical lines of weakness in the rock and they are slowly enlarged by carbonation. Over time, they are widened and deepened to form grikes. The slabs of rocks separating these are called clints and the resulting landscape is called a limestone pavement.

Another rock type that can produce a distinctive landscape in basalt. The Antrim-Derry Plateau is one such landscape that was formed when lava from a divergent plate boundary cooled quickly on the surface. Here, about 65 million years ago, the North American plate began to pull away from the Eurasian plate, and lava spilled from the mantle onto the surface.  The lava cooled rapidly to form the basalt. At the Giant’s Causeway, it is believed that the lava flowed into a river where it was cooled quickly and contracted to form the distinctive hexagonal pillars of basalt. Today the Giant’s Causeway is a world heritage site and a major tourist attraction.