Weathering slowly wears away exposed surfaces on rocks, roads and mountains alike. The length of time exposed rock remains exposed impacts its susceptibility to weathering.
Chemical weathering occurs when minerals in rocks interact with external agents like air or water. Oxygen can oxidize certain minerals while water can dissolve silicates entirely or convert silicates to clays, both processes affecting chemical weathering in different ways.
Water
Physical weathering involves breaking rocks into smaller and smaller pieces through processes such as exfoliation, freeze-thaw cycles, abrasion and root expansion. Water can also seep into cracks and crevices within rocks before eventually evaporating out, widening those cracks further as it evaporates away.
Chemical weathering involves altering mineral composition through chemical reactions. Since water-rich climates facilitate these chemical reactions, chemical weathering occurs more quickly.
Humans also contribute to chemical weathering through human activity. Sulfur dioxide produced when we burn fossil fuels such as coal or oil corrodes certain stone surfaces causing acid weathering effects on these areas.
Ice
Ice is present across Earth’s continents and surface waters in various shapes and sizes, from glaciers in Antarctica and Greenland to smaller masses known as ice caps forming on mountain tops and valley floors, covering many seas, rivers, lakes, etc.
Ice is weathered both physically and chemically. Physical weathering consists of breaking rocks apart physically without altering their chemical makeup; examples include freezing and expanding of water trapped between rock cracks, or when tree roots dig into rocks, while carbon dioxide in the air reacts with limestone rock to disintegrate it further.
Acids
Acids play an integral part in chemical weathering processes. Carbon dioxide in the atmosphere combines with rainwater to form carbonic acid, which works to dissolve rock. Fossil fuel combustion generates sulfuric and nitric acids that contribute to chemical weathering as well. Pollutants in the air may also trigger acid rainstorms that accelerate chemical weathering processes.
Acids can weather rocks through processes of hydration, hydrolysis and oxidation; these chemical reactions tend to take place more often in warm, damp climates; for instance, rust is often formed when iron-rich rock minerals combine with water and oxygen – this type of weathering can often be seen in limestone regions like Carlsbad Caverns in New Mexico.
Salts
At this time of year, when you see a salt truck or plow driving along roads, they’re there to keep them safe by spraying roads with salt-laden solutions that lower water’s freezing point and prevent it from freezing into ice crystals and creating hazards on our roadways.
Salts are chemical products of neutralization reactions between acids and bases, consisting of positively charged ions from one side and negatively charged ions from the other to form a crystal structure. Salts can be found both naturally as seawater as well as dry minerals like halite.
Rock salt’s effectiveness at combatting snow and ice depends on many variables: ground temperature, air temperature and even the type of pavement used can all impact its success.
Plants
Plants weather rocks through both chemical and physical processes. Their roots secrete acids that break down minerals while secretions produce acids to break apart more rock. Over time, their roots penetrate cracks in rocks to weaken and split apart more rocks – with climate conditions and soil quality both having an influence over weathering rates.
Mineralogy and structure determine how resistant a rock is to weathering. For instance, interlocking silicate grains of granite weather faster along crystal boundaries than those in layered sedimentary rocks. Furthermore, different minerals have differing degrees of solubility in water – for instance calcite dissolves more readily than feldspar, which explains why its surfaces tend to last longer.
Animals
Animals play an essential part in weathering. Plant roots may enter cracks in rocks and slowly expand outward, widening them further. Mole-like animals like moles can also help break apart rock layers and soil by burrowing underground and tunneling under.
Erosion involves transporting small pieces of weathered rock and minerals from one place to the next, altering its shape. It plays a critical role in creating soils from weathered rock combining with plant, animal and bacterial material to form new soil layers.
Watch how animals respond to weather fluctuations by watching how they respond, for instance some mammals developing thick winter coats to keep warm.