Weathering Flashcards
What is weathering?
The process in which rocks break down.
What are the different kinds of weathering?
Physical/ mechanical weathering
Chemical weathering
Biological weathering
What is physical/ mechanical weathering?
Mechanical weathering happens when rocks are broken into pieces by physical means due to several factors or causes.
What is freezing and thawing?
Cycles of freezing and thawing can cause ice wedging, which can break rock into pieces. The cycle of ice wedging starts when water seeps into cracks in a rock. When the water freezes, it expands and pushed against the cracks causing the cracks to widen. When the ice melts, the water seeps further into the cracks, as the cycle repeats, the cracks get bigger and finally, the rock breaks apart.
What is salt crystallization (Haloclasty)?
Saline water seeps into permeable rock and then evaporates, causing interstitial growth of salt crystals, which pry the rock grains or crystals apart. Occurs on coast and in deserts, saline water evaporates resulting in the formation of salt crystals. As the crystals become larger the exert pressure/ stress upon the rock result disintegration/ decomposition.
What is sheeting?
When rocks are exposed to the atmosphere, they release pressure resulting in the rock becoming weak, released pressure results in the development of cracks parallel to the surface.
What is thermal expansion or isolation?
Prominent in the desert environments with no clouds and vegetation. The outer layer of the rock cools very fast and heats up very rapidly, this induces stress causing the outer thickness to peel off like layers of an onion.
What is abrasion?
Abrasion is a kind of mechanical weathering that happens when rocks are worn away by contact with other rocks. Abrasion happens whenever one rock hits/ rubs another caused by water, wind, and gravity.
What is biological weathering?
Earthworms cause weathering by tunneling through the soil and move pieces of rock around. This motion breaks some of the rocks into smaller pieces. It also exposes more rock surfaces to other agent of weathering.
What is chelation?
It is a biological process where organisms produce organic substances, known as chelates, that can decompose minerals and rocks by removing metallic cations.
What is chemical weathering?
Chemical weathering happens when rocks break down because of chemical reactions actions.
What is hydrolysis?
Water can dissolve some of the elements that make up rocks. Even very hard rocks, such as granite, can be broken down by water. Hydrogen in water reacts with minerals in the rock. There is a combination of the H+ and OH- ions and the ions of the mineral. The rate of hydrolysis depends upon the composition of the air and water in the soil.
What is oxidation?
The process of addition and combination of oxygen to minerals. The absorption is usually from O2 dissolved in soil water and that present in the atmosphere. The reactions take place in moist conditions and result in hydrated oxides (e.g.) minerals containing Fe and Mg.
What is hydration?
Chemical combination of water molecules with minerals leading to a change in structure. Upon hydration there is swelling and increase in volume of minerals. The minerals lose their luster and become soft. Hydration occurs in minerals such as aluminium oxide, iron oxide and gypsum.
What is carbonation?
Carbon dioxide (CO2) when dissolved in water it forms carbonic acid. 2H2O + CO2 -> H2CO3. This carbonic acid attacks many rocks and minerals and brings them into solution.
