Weathering and erosion are natural processes that break down rock and soil to reveal hidden treasures underneath, like how canyons form over millions of years or fast forces like mudslides.
Weathering can be caused by various forces: water, ice, wind and living things such as plants – including freezing and expanding in cracks in rocks due to freezing; plant roots penetrating cracks to eventually pry them open over time.
Water
Water is one of the primary forces involved in weathering, erosion and deposition processes; thus it plays an integral part in creating various forms of sedimentary rock.
Rock minerals react with water to form new, soluble minerals that are carried away by rainwater or rivers – this chemical weathering process is common among hard rocks such as granite and other granite-like rocks.
Water can also play an essential part in mechanical weathering. As it freezes and expands, it can enlarge cracks in rocks while simultaneously breaking them up into smaller pieces. Plants and animals may also play their part, for instance with thorny plants growing near rocks to widen cracks while animals that tunnel underground can break apart rock and soil into fragments.
Ice
Water can erode rock surfaces both physically and chemically. River currents carry away soil while carrying rocks along their course, while carbonic acid in rainwater dissolves many types of rocks like limestone quickly causing caves and cliffs to form.
Glaciers can erode rocks. A glacier gradually moves downhill, scraping the ground and rocks it encounters and leaving behind sediment deposits that eventually wind their way into oceans.
Mechanical weathering occurs when liquid water penetrates cracks in rocks, freezes, expands them, and expands them again after expanding them with freezing. Road crews frequently have to repair potholes due to this phenomenon; but its beauty can also create stunning landscapes like New Zealand’s “Split Apple” rock formation.
Wind
Wind is a key factor in erosion. As it blows sand and dust against rocks it hits, the eroded material carries away by its currents until deposited elsewhere – often creating dunes, hills or other landforms in its path.
Rivers also have an enormous effect on Earth; their powerful waters erode rock into deep and wide river channels that carry away sediment to form delta soils that provide essential agricultural areas.
Sometimes chemical weathering causes rocks to disintegrate; for instance, iron-rich rocks turn rusty when wet and crumble into pieces. Also, expanding ice in cracks in rock can break it up mechanically – known as abrasion.
Living Things
Living things include any organism with a defined structure, need for energy, responds to stimuli and changes in its environment, has metabolism and life cycles involving growth, reproduction, movement, death and decay.
Living and nonliving processes alike can alter the shape of Earth’s surface through weathering, erosion and deposition.
Erosion is a mechanical process driven by water, gravity (see Chapter 10), wind or glaciers (see Chapter 14), transporting sediment (and rocks) to new locations.
Everyday we witness weathering and erosion – from cracks in roads to beach sand. Erosion can happen rapidly like with a mudslide or slowly like when water flows through a stream.
Gravity
Weathering and erosion sculpt the planet into ever-evolving works of art; their slow movement leaving visible effects over thousands or millions of years.
So many people take natural landscape-altering processes for granted that many take them for granted too, yet human activity remains one of the fastest landscape-altering forces on Earth – building cities, roads, farming, dams and levees, mining for metals coal and other resources change the planet more quickly than all natural erosional processes combined.
Erosion refers to all of the processes by which rock and other materials break down into sediments of different sizes, as well as being carried down slopes by water, wind, glaciers or gravity; this process is known as mass wasting.