How does ROCK TYPE affect LAND USE? By Helen Lee
There are THREE rock types... IGNEOUS SEDIMENTARY METAMORPHIC
IGNEOUS... Igneous rock is fire-formed rock, it is formed from magma (molten rock). Extrusive rock is formed when magma erupts to the surface and cools quickly. Intrusive igneous rock forms when the magma cools before reaching the surface. It cools very slowly, and this forms large crystals. One example of igneous rock is granite.
SEDIMENTARY... Sedimentary rock is formed when rock is eroded and is deposited in the sea and onto the sea bed by rivers and streams. The sediment builds up, and fuses together with the increasing pressure of the growing strata (layers). As the sea retreats, the sedimentary rock is exposed above land. One example of sedimentary rock is limestone (CaCO 3 .)
METAMORPHIC... Metamorphic rock is formed by intense heat and pressure. Sedimentary and igneous rock are transformed into metamorphic rock during volcanic activity or earth movements. The chemical composition of the rock remains exactly the same, but the new rock is harder and more compact. One example of metamorphic rock is marble, which is formed from limestone.
Qualities of rock Igneous rock, in general, is very hard and is resistant to erosion. The rock is also often filled with beautiful crystals. Our example granite is impermeable (it doesn’t let water soak through), and as a result produces lots of marshy areas and weak, acidic soil. These factors mean that igneous rock areas are seldom used for farming. Its resistance to erosion, however, makes it perfect for building material, and its toughness and crystals make it ideal for manufacturing work surfaces and gravestones.
Our example of sedimentary rock (limestone) produces karst scenery, which often features huge caves and gorges. These can attract tourists to take up hobbies like rock climbing, and also attracts tourists with its spectacular views and unusual features such as limestone pavements. As well as this, limestone is easily crafted and shaped, and often contains fossils (from the sediment layers). These factors make limestone ideal for building material and crafting pillars and intricate patterns. However, limestone is very vulnerable to solution erosion, and has to be replaced over time.
Because of its hardness and resistance to erosion, marble can be used for many of granite’s uses. For example, marble is often used to manufacture work surfaces, staircases and gravestones.