What makes weathering happen

For example, a rabbit can burrow into a crack in a rock making it bigger and eventually splitting the rock, or a plant may grow in a crack in a rock and, as its roots grow, cause the crack to widen. Even you can be a source of weathering! Boots and shoes walking over the same patch of rock may eventually wear down the rock.

Chemical weathering describes the process of chemicals in rainwater making changes to the minerals in a rock. Carbon dioxide from the air is dissolved in rainwater, making it slightly acidic.

A reaction can occur when the rainwater comes into contact with minerals in the rock, causing weathering. Physical weathering occurs when physical processes affect the rock, such as changes in temperature or when the rock is exposed to the effects of wind, rain and waves. Each process has a distinct effect on rocks and minerals. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering.

Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Weathering is the wearing away of the surface of rock, soil, and minerals into smaller pieces.

Example of weathering: Wind and water cause small pieces of rock to break off at the side of a mountain. There are four main types of weathering. These are freeze-thaw, onion skin exfoliation , chemical and biological weathering. Most rocks are very hard. However, a very small amount of water can cause them to break.

Chemical weathering occurs when water dissolves minerals in a rock, producing new compounds. Hydrolysis occurs, for example, when water comes in contact with granite. Feldspar crystals inside the granite react chemically, forming clay minerals.

The clay weakens the rock, making it more likely to break. There are different types of chemical weathering processes, such as solution, hydration, hydrolysis, carbonation, oxidation, reduction, and chelation. Some of these reactions occur more easily when the water is slightly acidic.

Limestone rocks dissolving in water Plant roots growing through concrete and splitting it Waves carrying sand away from a beach A large rock splitting into pieces because of ice.

Examples of mechanical weathering include frost and salt wedging, unloading and exfoliation, water and wind abrasion, impacts and collisions, and biological actions.

All of these processes break rocks into smaller pieces without changing the physical composition of the rock. Power washing cement or asphalt surfaces, and weeding regularly, will prevent the breaking down of such surfaces from the decomposition induced by acids released by lichens or mosses. When the smaller rock pieces now pebbles, sand or soil are moved by these natural forces, it is called erosion. Different minerals weather at different rates. Mafic silicates like olivine and pyroxene tend to weather much faster than felsic minerals like quartz and feldspar.

Different minerals show different degrees of solubility in water in that some minerals dissolve much more readily than others. Water dissolves calcite more readily than it does feldspar, so calcite is considered to be more soluble than feldspar.

Massive rocks like granite generally to not contain planes of weakness whereas layered sedimentary rocks have bedding planes that can be easily pulled apart and infiltrated by water. Weathering therefore occurs more slowly in granite than in layered sedimentary rocks.

Rainfall and temperature can affect the rate in which rocks weather. High temperatures and greater rainfall increase the rate of chemical weathering. Rocks in tropical regions exposed to abundant rainfall and hot temperatures weather much faster than similar rocks residing in cold, dry regions.

Soils affect the rate in which a rock weathers. Soils retain rainwater so that rocks covered by soil are subjected to chemical reactions with water much longer than rocks not covered by soil. Soils are also host to a variety of vegetation, bacteria and organisms that produce an acidic environment which also promotes chemical weathering.

Minerals in a rock buried in soil will therefore break down more rapidly than minerals in a rock that is exposed to air. The longer a rock is exposed to the agents of weathering, the greater the degree of alteration, dissolution and physical breakup. Lava flows that are quickly buried by subsequent lava flows are less likely to be weathered than a flow which remains exposed to the elements for long periods of time. Chemical weathering is a process where minerals in a rock may be converted into clays, oxidized or simply dissolved.

Silicates comprise almost all minerals in igneous rocks and are also important components in metamorphic rocks. Not all silicates, however, survive weathering processes to become incorporated into sedimentary rocks.

Mechanical weathering , also called physical weathering, breaks rock into smaller pieces. These smaller pieces are just like the bigger rock, just smaller. That means the rock has changed physically without changing its composition.

The smaller pieces have the same minerals, in just the same proportions as the original rock. There are many ways that rocks can be broken apart into smaller pieces.

Ice wedging , also called freeze-thaw weathering , is the main form of mechanical weathering in any climate that regularly cycles above and below the freezing point. Ice wedging works quickly, breaking apart rocks in areas with temperatures that cycle above and below freezing in the day and night, and also that cycle above and below freezing with the seasons. Ice wedging breaks apart so much rock that large piles of broken rock are seen at the base of a hillside called talus.

Abrasion is another form of mechanical weathering. In abrasion, one rock bumps against another rock. Now that you know what mechanical weathering is, can you think of other ways it could happen? Plants and animals can do the work of mechanical weathering. Burrowing animals can also break apart rock as they dig for food or to make living spaces for themselves. Mechanical weathering increases the rate of chemical weathering.

As rock breaks into smaller pieces, the surface area of the pieces increases. With more surfaces exposed, there are more surfaces on which chemical weathering can occur. Chemical weathering is the other important type of weathering. Chemical weathering is different from mechanical weathering because the rock changes, not just in size of pieces, but in composition.

That is, one type of mineral changes into a different mineral. Chemical weathering works through chemical reactions that cause changes in the minerals. Most minerals form at high pressure or high temperatures deep in the crust, or sometimes in the mantle.