An article about Different Types of Weathering.
Different Types of Weathering
All surfaces that are exposed to the weather are attacked by weathering. Metal rusts, roads crack, statues crumble, and rocks and buildings break up. Evidence of the effect of the weather can be seen everywhere. There are three types of weathering.
This is where rocks are broken down into smaller and smaller particles. One way in, which this happens, is through freeze-thaw action. Water that has collected in cracks and hollows in the rock will freeze when temperatures fall below 0 Celsius. As it does so it expands, increasing the pressure on the rock. When it thaws the pressure is released. Repeated freezing and thawing causes the rock to weaken and crumble, so eventually the crack becomes wider. Whole blocks of rock can break off in this way. Freeze-thaw action is commonest in mountain areas where temperatures fluctuate around 0 Celsius for much of the year.
As rainwater falls through the air it becomes a very weak type of acid. When this acidic water comes into contact with rock it starts to dissolve it. The rate at which is dissolves depends on the type of rock. Limestone, for example, dissolves very quickly. Many buildings are built partly of limestone and the results of chemical weathering can be clearly seen. Oxygen in the air can sometimes react with iron in the rocks so that they change to a deep red colour – the rocks actually become rusty.
Pollution in towns and cities increases chemical weathering. This can be seen on blackened buildings. Just like physical weathering, the presence of water is essential for chemical weathering to take place. The rate at which chemical weathering takes place depends on the temperature. The warmer it is, the more rapid the chemical decay.
Animals and plants also cause weathering. Seeds may fall into the cracks in the rocks. As water usually collects there, it forms ideal conditions for the seed to germinate and grow. As the plant develops, its roots may push the rocks apart. Animals burrowing into the soil can also cause damage.