Weathering refers to the physical and chemical breakdown of rocks and minerals near Earth’s surface by interaction between air, water and plants or animals.
Erosion is an ongoing process that transforms Earth’s rocks into ever-evolving works of art, serving as the precursor for soil formation.
Water
Water is the main weathering agent, helping dissolve and weaken rocks through chemical processes like carbonation, hydration, oxidation and more. Carbon dioxide reacts with moisture in the atmosphere to form acid rain which accelerates chemical weathering while plants and animals that dig, trample or tunnel through rocks and soil can contribute to physical weathering processes as well.
Mechanical weathering breaks rocks down into smaller fragments without altering their chemical makeup and composition of minerals that comprise them. For instance, when clay near rocks absorbs water it may expand, leading to exfoliation – or cracks filled with liquid can freeze up and expand as they freeze up, leading to fragmentation of rock surface layers and further breaking apart of their formations.
Ice
Ice is one of nature’s most powerful weathering agents, helping create and reveal its magnificent creations – from waterfalls high in mountains, to sandstone arches in desert landscapes, and polished cliffs facing violent seas.
Mechanical weathering or physical weathering is the process by which rocks are broken down physically into smaller pieces by water seeping into cracks and crevices in rocks, then freezing at night – with this frozen water acting like a wedge to gradually widen cracks between rocks, splitting rocks apart.
To determine the thickness of ice, use an outdoor small object covered in ice such as a tree branch to take measurements. Place a ruler along its edge near where you think there is thickest part of ice and write down measurement details.
Acids
Acids are strong chemicals that corrode natural materials. When combined with bases, they react and form salts – also acting as catalysts in chemical weathering processes.
Different minerals weather at differing rates; for instance, feldspar can deteriorate more easily than quartz. Climate also plays a significant role; warmer temperatures expedite chemical reactions.
Fossil fuel burning accelerates chemical weathering. Burning coal, oil, and natural gas releases nitrogen oxide and sulfur dioxide into the air which then transform into acids before raindrops eventually fall back down on Earth as precipitation. This type of precipitation known as acid rain rapidly weathers limestone, marble, and other types of stone surfaces.
Salts
Salt helps keep roads clear during winter snow and ice storms by interfering with water’s ability to freeze, helping prevent roads from being covered in ice or snow. When roads become covered in either, road crews or plows use deicing chemicals such as rock salt to treat them accordingly.
Chemical properties of various salts vary wildly. While some have a “salty” taste, others, like lead diacetate and potassium bitartrate, possess bitter or sour characteristics that differ significantly. Furthermore, ammonium chloride – commonly used in lithography and photographic development – emits an unpleasant odor.
Many salts are anhydrous, or devoid of water in their crystalline structures, like table salt (NaCl). Others may contain moisture such as copper sulfate pentahydrate and cobalt nitrate; yet others can even be zwitterionic, consisting of both anions and cations within one molecule like amino acids.
Plants
Plants don’t just add beauty or taste; they also impact the chemistry of rocks. Chemical weathering occurs when minerals break down by reacting with substances in their environment – carbonic acid in rain or humic acids in soil are two examples – while plants that secrete acid or even symbiotic bacteria that weather minerals help speed this process up.
Mechanical weathering breaks rocks down without altering the mineral makeup of the rock itself, through processes like freeze-thaw cycles, abrasion and wet/dry cycles. Other forms of mechanical weathering include tree roots encroaching into cracks and crevices to gradually widen them over time or water erosion by “salt wedging”. Abrasion wears down sharp or jagged edges on beach stones.
Animals
Animals, plants and other living things can influence weathering by moving through it and altering its surface. For instance, rabbits’ tunneling activity might widen a crack in a rock surface further and eventually fracture it apart.
Animals also help weather rocks by adapting their body temperatures to match those around them. When temperatures reach high levels, animals might adjust by becoming lethargic and sleeping through the day or becoming active at dawn and dusk when temperatures decrease; or become nocturnal to take advantage of cooler temperatures.
Animals have long been believed to be adept at foretelling the weather. Groundhogs’ predictions about winter length, cows lying down when it looks likely to rain and crickets chirping more quickly as temperatures increase are all examples of animals acting as barometers for weather patterns.