Weathering, or the gradual decomposition or dissolution of rocks and minerals on Earth, is caused by factors like water, ice, acid rain, salts, plants, animals and temperature changes.
Chemical weathering includes processes such as oxidation (the formation of compounds such as rust), carbonic acid formation from rainwater reacting with carbon dioxide in the air; hydrolysis; and conversion of silicates into clays.
Water
Water is a key agent in weathering. Its powerful flow can erode rocks by washing away soil or rock particles – this process is known as mechanical weathering.
Water can also play an integral part in chemical weathering. For instance, carbonic acid in water seeping into cracks in limestone can dissolve it over time through chemical weathering.
Chemical weathering can be hastened by human activities like burning fossil fuels and emitting gases into the atmosphere, which then transform into acids that form acid rain that eventually falls back down as raindrops onto Earth, damaging plants, metals and buildings as it falls. Acid rain is known for being harmful to both humans and nature alike. It has even killed fish and destroyed buildings!
Ice
Ice is an integral component of Earth’s water and rock cycle. It continually weathers away at rocks’ surfaces, contributing to erosion over longer timescales.
Physical weathering (also called mechanical weathering) involves breaking rocks apart without altering their composition, usually by means of friction with other rocks or even themselves. Ice wedging is one form of physical weathering often seen in climates which fluctuate above and below freezing on an irregular basis – including Idaho high country climates.
Acids
Chemical weathering alters the mineral makeup of rocks through processes known as oxidation and dissolution. Oxidation involves minerals combining with oxygen to form new minerals – for instance iron-bearing minerals may oxidize to form rust as they interact with oxygen in the environment.
Chemical weathering occurs when minerals interact with other substances to change their shape, size or structure – for instance feldspar can chemically react with water to form clay.
An acid is any chemical compound which increases the concentration of hydronium ions in solution, with reddening blue litmus paper as evidence of increased hydronium ion concentration, or reacting with bases or metals to form salts. In practice, an acid may taste sour and redden blue litmus paper to be classified as such an acid.
Salts
As snow and ice cover roads across the nation this time of year, many areas rely on rock salt as a preventive measure to treat roads. Salt has the unique property of lowering water’s freezing point point thus keeping it from becoming ice.
Based on their chemistry and crystal structures, different salts exhibit various properties. Some salts such as lead diacetate or hydrogen cyanide may produce an unpleasant flavor or aroma while potassium bitartrate or saline offer salty tastes and smells. Most nonvolatile salts are generally nonodorous except those formed from strong acids or bases – such as those formed from cyanide salts with their characteristic almond scent.
Plants
Plants play an integral part in physical weathering. Their roots can travel into cracks in rocks, altering their chemistry and making them easier to break apart, while simultaneously altering the local environment by absorbing and decomposing organic material from rocks.
Root systems of certain plants can facilitate mycorrhizal fungi to form within their root systems and release inorganic nutrients, increasing their effectiveness at breaking apart minerals and dissolving them, as well as speeding up chemical weathering rates.
Carbon dioxide in the air mixes with rainwater to form carbonic acid, a weak acid which quickly weathers limestone and other types of rock. This effect is accelerated in humid tropical climates with frequent freeze-thaw cycles as well as by iron oxides coming into contact with oxygen that quickly produce oxides such as rust.
Animals
Even though it remains uncertain whether animals can accurately forecast the weather, farmers sometimes know of an approaching cold front before meteorologists do – often attributing this insight to animal behavior, like groundhogs signaling length of winter or cows lying down ahead of an onslaught of storms.
Animals contribute to weathering in various ways. Fungi and algae living together to form lichen help break down rock minerals; other animals dig and trample rocks causing mechanical weathering; plant roots can wear away at rocks by growing into cracks or crevices and eventually wedge open, eventually breaking the crack open completely.