Weathering

Some ways weathering affects building;

Sun cause the paint to peel Rain makes metal objects rust Hot and cold temperatures weaken surfaces Plants break up the bricks

Concept of weathering

All things on earths surface are affected by the action of the weather. Weathering describes all processes that break down rocks, soil and other objects on the earth's surface. Weathering happens in one place. We can see the effects of weathering on constucted features such as buildings.

Carbonation

As rain passes through atmosphere it mixes with chemicals to make weak acids. For example, rain combines with carbon dioxide to make carbonic acid. Carbonic acid attacks a mineral called calcium carbonate. Calcium carbonate is the main mineral in certain kinds of limestone rock. Carbonic acid changes calcium carbonate into the mineral calcium bicarbonate. Calcium bicarbonate is soluble. This means it can be washed away in water, causing weathering in the process. This process is called carbonation. Carbonation can produce very interesting cab features.

Biological weathering

Biological weathering is weathering caused by the action of plants and animals. you may have seen we screen cracks in roads and concrete. as these roots grow they break up the soil and can cause rocks and pavements to split and break up as well. Plants and animals may release chemicals that cause chemical weathering. for example tiny plants called lichens grow on rocks. Lichens produce dilute acidic solution that causes some minerals in rocks to break down the tiny roots of lichens also physically breakdown small grains off rocks. Decaying remains of dead plants and soil may form organic acids which, when dissolved in water, cause chemical weathering. animals barring into the soil and also we can rocks or expose rocks and soil to physical and chemical weathering

The impact of human activities on weathering:name human activities that can increase physical chemical and biological weathering

Building settlements Making farms Digging mines Building roads and railways

Exfoliation

Exfoliation is a kind of physical weathering caused by bid day and night temperature changes such as those in desert and semi-desert areas. Exfoliation mean shedding or casting off in layers. This is what happens to rocks affected by this type of weathering.

Exfoliation process

Extreme daytime heating causes outer rock layers to heat up and expand away from the cooler internal parts of rock. At night, when the temperature drops quickly, the outer layers cool and contract. The constant expanding and contracting weakens outer layers of the rock Eventually outer layers flake off

Frost shattering

Frost shattering is caused by the constant freezing and thawing of water in cracks in rocks. Frost shattering occurs mainly in mountain ares where temperatures often drop below freezing. Ice takes up 10% more space than water. The expanded ice puts pressure on the cracks in the rock. Repeated expanding and contracting of water and ice weakens the rock, causing small pieces to shatter and fall off.

The impacts of human activities on physical weathering

Human activity exposes rocks and soil to the action of the weather. For example, mine shafts and tunnels weaken rocks, causing them to break and collapse. Making roads involves moving thousands of tons of soil and rocks. A new road exposes rocks and soil to physical weathering processes such as frost shattering and exfoliation

Process of acid rain

Industries and cities produce sulphur dioxide And nitrous oxide Gases combine with the water in the atmosphere to produce acids (H2SO4 and HN03) Acid rain kills plants, pollutes lakes and rivers and causes chemical weathering

The impact of human activities on biological weathering

Many human activities can increase biological weathering. For example, making a vegetable garden exposes rocks and soil to attack from all three kinds of weathering: physical, chemical and biological

How farming speed up different kinds of weathering

Natural vegetation is removed to make fields. Chemicals added to soil . Burrowing animals (moles, worms) attracted to food on the farm. Soil regularly ploughed. Animals walk over rocks and soil. Bare soil exposed to the weather.

Oxidation

Oxidation is another kind of chemical weathering. It occurs when oxygen from air dissolves in water and combines with chemicals in the rocks to form oxides.if the rock contains a lot of iron, then oxidation produces a brown material called iron oxide. This looks like rust on the rock. Oxidation weakens rocks and causes them to crumble.

The impact of human activities on chemical weathering

People burn fossil fuel is such as coal, oil and natural gas for energy to cook, power vehicles and generate electricity. When fossil fuels are burnt, chemicals such as Carbon dioxide, nitrous oxide and Sulphur dioxide are released into the air. These chemicals dissolve in the water in clouds and increase chemical weathering. Rain that falls from these clouds is called acid rain. Acid rain is a human cause of chemical weathering. Acid rain also damages plants. When it washes into lakes and rivers, it increases the acidity of the water, which causes fish and out the water organisms to die. Constructed features such as stone buildings and statues are also damaged by the effects of acid rain.

Physical weathering

Physical weathering happens when a physical force breaks rocks into small pieces. Small scale physical weathering removes grains of rock one grain at a time. Large scale physical weathering causes large pieces of rock to break away from mountains and crash down the slopes. Temperature and water are two main causes of physical weathering. The most common kind of physical weathering is called frost shattering

Chemical weathering

Rocks are made up of different minerals. Different rocks have their own chemical composition. Chemical weathering changes the chemical composition of the minerals in rocks. This weakens rocks, causing them to break up and wear away. Two examples of chemical weathering are carbonation and oxidation

Frost shattering proccess

Water collects in cracks in rocks Water at the top of the cracks freeze first to form a cap of ice Ice has to expand sideways Pressure from ice weakens the rock Rock pieces eventually fall off

Carbonation process

Water seeps through cracks and joints in the rock Carbonation dissolves rocks, forming caves and underground features