Weathering is a major process which has helped shape the landforms of New Zealand. Weathering is a process of rock being constantly worn away and broken down by the weather or the actions of plants and animals. Weathering is divided into two major groups: Chemical weathering and Physical weathering. Chemical weathering happens when chemicals, such as acid in rain water, gradually dissolve and eat away at rocks. For example, limestone rock dissolved by rain water is responsible for many caves and gorges in New Zealand, including the Waitomo caves. The picture on the right is a picture of a cave in the Castle Hill basin, Canterbury, which has been formed by rain water dissolving limestone. This causes the limestone to wear away and create a new shape. Physical weathering makes rocks break apart in sheets, blocks or grains. It can further be divided into three categories: Exfoliation, Freeze-thaw action and biological weathering. Exfoliation is when Rocks which are warmed by the sun expand and shrink as they cool at night. The outer layer of the rock expands more, because it is directly exposed to the suns heat, and soon it separates from the rock and peels off. Freeze-thaw action is when water seeps into cracks in a rock and then freezes and expands. As the temperature…
