Oxidation is the type of chemical weathering that causes rust.
A process called "weathering" is responsible for most of the changes made to the geology of the earth’s surface. It can be affected by different factors, and is grouped into two major categories: mechanical and chemical. Chemical weathering causes a reaction within the minerals of a rock to change the overall structure of that rock in some way.
Definition
Chemical weathering is when a reaction happens involving water to add or remove elements from a mineral within a rock structure. It occurs on the Earth’s surface as it reacts with the outside environment. Chemical weathering does not happen under the surface because conditions there remain stable. Mechanical weathering differs from chemical weathering in that it breaks down rock structure by physical effects, such as abrasion from rocks grinding together or water freezing within cracks.
Hydrolysis
This type of chemical weathering usually happens in silicate minerals, turning them into clay minerals with the introduction of water. Water comes in and breaks apart to become an H+ and an OH-, which causes minerals to become part of a solution, changing the structure of the mineral.
Dissolution
This usually happens to limestone or marble because they contain calcite, which dissolves in acidic water. The acidic water can come from acid rain or it can be natural, but it breaks down the rock, which can form sink holes, or caverns. Dissolution is also known as solution.
Oxidation
This type of chemical weathering is what causes rust. Oxygen that is dissolved in water reacts with the minerals that contain iron, such as hemotite and limonite. This will turn the rock and soil around it a brownish red color. It will also get weaker and crumble once it has rusted. It usually is only apparent on the surface of the rock, but if there are cracks, you will see the oxidation moving down into the rock's interior.
Biological Weathering
When carbon dioxide and water come together, they form carbonic acid. The more carbon dioxide available, the more easily this happens. The carbonic acid is acidic, and so breaks down the minerals within rocks like calcite. Plants and other organisms that live on rocks can cause chemical weathering. Respiration of the organism releases extra carbon dioxide, which can cause carbonation of the rock. This alters the pH of the rock. Also, pants can produce structures called chelates that will decompose rocks.
Tags: breaks down, carbon dioxide, type chemical, type chemical weathering, acidic water, breaks down rock, carbonic acid
