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You cannot download interactives. The rock cycle is a web of processes that outlines how each of the three major rock types—igneous, metamorphic, and sedimentary—form and break down based on the different applications of heat and pressure over time. For example, sedimentary rock shale becomes slate when heat and pressure are added. The more heat and pressure you add, the further the rock metamorphoses until it becomes gneiss.
If it is heated further, the rock will melt completely and reform as an igneous rock. Empower your students to learn about the rock cycle with this collection of resources. Erosion is the process where rocks are broken down by natural forces such as wind or water. There are two main types of erosion: chemical and physical. In physical erosion, the rock breaks down but its chemical composition remains the same, such as during a landslide or bioerosion, when plants take root and crack rocks.
Explore the process of erosion with this collection of resources. Weathering is the process of the weakening and breakdown of rocks, metals, and manmade objects. There are two main types of weathering: chemical and physical. An example of chemical weathering is acid rain. Caused mostly by the burning of fossil fuels, acid rain is a form of precipitation with high levels of sulfuric acid, which can cause erosion in the materials in which it comes in contact. An example of physical weathering is wind blowing across the desert playas.
This process causes rocks to form a specific pyramid-like shape and they are called ventifacts. Select from these resources to teach about the process of weathering in your classroom. Meet Walter, a friendly animal who will guide you on your quest for knowledge about erosion and weathering. You will begin your journey by doing different activities to that will simulate weathering and erosion.
The game continues with a variety of activities and information. At the end, you will play a bonus arcade game to award you for your good work.
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Encyclopedic Entry Vocabulary. Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. A similar process, weathering , breaks down or dissolve s rock , but does not involve movement. Erosion is the opposite of deposition , the geological process in which earthen materials are deposited, or built up, on a landform.
Most erosion is performed by liquid water, wind, or ice usually in the form of a glacier. If the wind is dust y, or water or glacial ice is muddy, erosion is taking place. The brown color indicates that bits of rock and soil are suspended in the fluid air or water and being transported from one place to another.
This transported material is called sediment. Physical erosion describes the process of rocks changing their physical properties without changing their basic chemical composition. Physical erosion often causes rocks to get smaller or smoother. Rocks erode d through physical erosion often form clastic sediments. Clastic sediment s are composed of fragments of older rocks that have been transported from their place of origin. Landslide s and other forms of mass wasting are associated with physical weathering.
These processes cause rocks to dislodge from hillsides and crumble as they tumble down a slope. Plant growth can also contribute to physical erosion in a process called bioerosion.
Plants break up earthen materials as they take root, and can create cracks and crevice s in rocks they encounter. Ice and liquid water can also contribute to physical erosion as their movement forces rocks to crash together or crack apart. Some rocks shatter and crumble, while others are worn away. River rocks are often much smoother than rocks found elsewhere, for instance, because they have been eroded by constant contact with other river rocks.
Liquid water is the major agent of erosion on Earth. Rain, rivers, floods, lakes, and the ocean carry away bits of soil and sand and slowly wash away the sediment. Rainfall produces four types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion.
Gullies carry water for brief periods of time during rainfall or snowmelt but appear as small valley s or crevasse s during dry season s. Valley erosion is the process in which rushing stream s and rivers wear away their bank s, creating larger and larger valleys.
The Fish River Canyon, in southern Namibia, is the largest canyon in Africa and a product of valley erosion. Over millions of years, the Fish River wore away at the hard gneiss bedrock, carving a canyon about kilometers 99 miles in length, 27 kilometers 17 miles wide, and meters 1, feet deep. See Chapter 16, Energy and Mineral Resources, for a more in-depth look at these fossil -derived energy sources. In contrast to detrital sediment , chemical, biochemical , and organic sedimentary rocks are classified based on mineral composition.
Most of these are monomineralic, composed of a single mineral , so the rock name is usually associated with the identifying mineral. Chemical sedimentary rocks consisting of halite are called rock salt. Rocks made of Limestone calcite is an exception, having elaborate subclassifications and even two competing classification methods: Folk Classification and Dunham Classification.
The Folk Classification deals with rock grains and usually requires a specialized, petrographic microscope. The Dunham Classification is based on rock texture , which is visible to the naked eye or using a hand lens and is easier for field applications.
Most carbonate geologists use the Dunham system. Sedimentary rock identification chart. Which of the following is a biochemical sedimentary rock? Coquina , chalk , and fossiliferous limestone are forms of biochemical rocks since their components are precipitated by organisms. Shale and sandstone are detrital even if they include fossils , banded iron formation is chemical, and coal Former swamp-derived plant material that is part of the rock record.
What is the most likely cause of a detrital sediment with highly rounded grains? The general rule of thumb is: the longer the transport distance, the more the rounding. Clastic or detrital rocks are categorized based on their grain size i.
Conglomerates are rounded, and breccias are angular. All chemical rocks are names based on composition i. Shale is the fissile , very fine grained sedimentary rock and splits easily into thin layers. Sedimentary structures are visible textures or arrangements of sediments within a rock. Geologists use these structures to interpret the processes that made the rock and the environment in which it formed.
They use uniformitarianism to usually compare sedimentary structures formed in modern environments to lithified counterparts in ancient rocks. Below is a summary discussion of common sedimentary structures that are useful for interpretations in the rock record. The most basic sedimentary structure is bedding planes , the planes that separate the layers or strata in sedimentary and some volcanic rocks.
Visible in exposed outcroppings, each bedding plane indicates a change in sediment deposition conditions. This change may be subtle. For example, if a section of underlying sediment firms up, this may be enough to create a form a layer that is dissimilar from the overlying sediment. Each layer is called a bed A specific layer of rock with identifiable properties. As would be expected, bed A specific layer of rock with identifiable properties.
Technically, a bed A specific layer of rock with identifiable properties. A layer thinner than 1 cm 0. Varves are bedding planes created when laminae and bed A specific layer of rock with identifiable properties. Varves are valuable geologic records of climatic histories, especially those found in lakes and glacial deposits. Graded bedding refers to a sequence of increasingly coarse- or fine-grained sediment layers.
Graded bedding often develops when sediment deposition occurs in an environment of decreasing energy. A Bouma sequence is graded bedding observed in clastic rock called turbidite. Bouma sequence bed A specific layer of rock with identifiable properties. These subsea density flows begin when sediment is stirred up by an energetic process and becomes a dense slurry of mixed grains.
The sediment flow courses downward through submarine channels and canyons due to gravity acting on the density difference between the denser slurry and less dense surrounding seawater. As the flow reaches deeper ocean basins it slows down, loses energy, and deposits sediment in a Bouma sequence of coarse grains first, followed by increasingly finer grains see figure. In fluid systems, such as moving water or wind, sand is the most easily transported and deposited sediment grain.
Smaller particles like silt and clay are less movable by fluid systems because the tiny grains are chemically attracted to each other and stick to the underlying sediment. Under higher flow rates, the fine silt and clay sediment tends to stay in place and the larger sand grains get picked up and moved. Bedforms are sedimentary structures created by fluid systems working on sandy sediment.
Grain size , flow velocity, and flow regime or pattern interact to produce bedforms having unique, identifiable physical characteristics. Flow regimes are divided into upper and lower regimes, which are further divided into uppermost, upper, lower, and lowermost parts. The table below shows bedforms and their associated flow regimes. For example, the dune A large pile of sediment, deposited perpendicular to flow. Internal bedding in dunes dips toward flow direction i. Formed in the upper part of the lower flow regime.
Plane bed A specific layer of rock with identifiable properties. The flat, parallel layers form as sandy sediment piles and move on top of layers below.
Even non-flowing fluid systems, such as lakes, can produce sediment plane bed A specific layer of rock with identifiable properties. They may look identical to lower-flow-regime bed A specific layer of rock with identifiable properties. Ripples are known by several names: ripple marks, ripple cross bed A specific layer of rock with identifiable properties.
The ridges or undulations in the bed A specific layer of rock with identifiable properties. With the exception of dune A large pile of sediment, deposited perpendicular to flow. Occasionally, large flows like glacial lake outbursts, can produce ripples as tall as 20 m 66 ft. First scientifically described by Hertha Ayrton, ripple shapes are determined by flow type and can be straight-crested, sinuous, or complex.
Asymmetrical ripples form in a unidirectional flow. Symmetrical ripples are the result of an oscillating back-and-forth flow typical of intertidal swash zones. Climbing ripples are created from high sedimentation rates and appear as overlapping layers of ripple shapes see figure. Cross bedding happens when ripples or dune A large pile of sediment, deposited perpendicular to flow. Desert sand dune A large pile of sediment, deposited perpendicular to flow.
British geologist Agnold considered only Barchan and linear Seif dune A large pile of sediment, deposited perpendicular to flow. Other workers have recognized transverse and star dunes as well as parabolic and linear dunes anchored by plants that are common in coastal areas as other types of dune A large pile of sediment, deposited perpendicular to flow.
The biggest difference between river dune A large pile of sediment, deposited perpendicular to flow. Some famous air-formed dune A large pile of sediment, deposited perpendicular to flow. As airflow moves sediment along, the grains accumulate on the dune A large pile of sediment, deposited perpendicular to flow. The angle of the windward side is typically shallower than the leeward downwind side, which has grains falling down over it.
This difference in slopes can be seen in a bed A specific layer of rock with identifiable properties. There are typically two styles of dune A large pile of sediment, deposited perpendicular to flow. In tidal locations with strong in-and-out flows, dune A large pile of sediment, deposited perpendicular to flow. This produces a feature called herringbone cross bedding. Another dune A large pile of sediment, deposited perpendicular to flow.
These bed A specific layer of rock with identifiable properties. Antidunes are so named because they share similar characteristics with dune A large pile of sediment, deposited perpendicular to flow.
While dune A large pile of sediment, deposited perpendicular to flow. Antidunes form in phase with the flow; in rivers they are marked by rapids in the current. Antidunes are rarely preserved in the rock record because the high flow rates needed to produce the bed A specific layer of rock with identifiable properties. Bioturbation is the result of organisms burrowing through soft sediment , which disrupts the bedding layers.
These tunnels are backfilled and eventually preserved when the sediment becomes rock. Bioturbation happens most commonly in shallow, marine environments, and can be used to indicate water depth. Mudcracks occur in clay-rich sediment that is submerged underwater and later dries out.
When this waterlogged sediment begins to dry out, the clay grains shrink. The sediment layer forms deep polygonal cracks with tapered openings toward the surface, which can be seen in profile.
The cracks fill with new sediment and become visible veins running through the lithified rock. These dried-out clay bed A specific layer of rock with identifiable properties. What makes this sedimentary structure so important to geologists, is they only form in certain depositional environments —such as tidal flats that form underwater and are later exposed to air. Syneresis cracks are similar in appearance to mudcracks but much rarer; they are formed when subaqueous underwater clay sediment shrinks.
Sole marks are small features typically found in river deposits. They form at the base of a bed A specific layer of rock with identifiable properties.
They can indicate several things about the deposition conditions, such as flow direction or stratigraphic up-direction see Geopetal Structures section. Flute casts or scour marks are grooves carved out by the forces of fluid flow and sediment loads. The upstream part of the flow creates steep grooves and downstream the grooves are shallower.
The grooves subsequently become filled by overlying sediment , creating a cast Material filling in a cavity left by a organism that has dissolved away. Formed similarly to flute casts but with a more regular and aligned shape, groove casts are produced by larger clasts or debris carried along in the water that scrape across the sediment layer.
Tool marks come from objects like sticks carried in the fluid downstream or embossed into the sediment layer, leaving a depression that later fills with new sediment. Load cast Material filling in a cavity left by a organism that has dissolved away. Like their name implies, raindrop impressions are small pits or bumps found in soft sediment.
While they are generally believed to be created by rainfall, they may be caused by other agents such as escaping gas bubbles. Imbrication is a stack of large and usually flat clasts—cobbles, gravels, mud chips , etc. The clasts may be stacked in rows, with their edges dipping down and flat surfaces aligned to face the flow see figure.
Or their flat surfaces may be parallel to the layer and long axes aligned with flow. Imbrications are useful for analyzing paleocurrents , or currents found in the geologic past, especially in alluvial deposits. Geopetal structures , also called up-direction indicators, are used to identify which way was up when the sedimentary rock layers were originally formed. This is especially important in places where the rock layers have been deformed, tilted, or overturned.
Well preserved mudcracks , sole marks , and raindrop impressions can be used to determine up direction. Other useful geopetal structures include:. When mud dries out, mudcracks can form.
These only form in conditions where land can be covered by water, then uncovered and dried. Ripples are formed in the slowest flows of the features listed, with speeds right above sediments laid down in flat laminae. Next fastest are cross bed A specific layer of rock with identifiable properties. Which of these can indicate a paleocurrent and show the direction water has flowed in the past?
Asymmetrical ripple marks show a current flowed in the past and indicates the direction it flowed. The ultimate goal of many stratigraphy studies is to understand the original depositional environment. Knowing where and how a particular sedimentary rock was formed can help geologists paint a picture of past environments—such as a mountain glacier , gentle floodplain , dry desert, or deep-sea ocean floor. The study of depositional environments is a complex endeavor; the table shows a simplified version of what to look for in the rock record.
Marine depositional environments are completely and constantly submerged in seawater. Their depositional characteristics are largely dependent on the depth of water with two notable exceptions, submarine fans and turbidites. Abyssal sedimentary rocks form on the abyssal plain. The plain encompasses relatively flat ocean floor with some minor topographical features, called abyssal hills. These small seafloor mounts range m to 20 km in diameter, and are possibly created by extension.
Most abyssal plains do not experience significant fluid movement, so sedimentary rock formed there are very fine grained. There are three categories of abyssal sediment. Calcareous oozes consist of calcite -rich plankton shells that have fallen to the ocean floor. An example of this type of sediment is chalk.
Siliceous oozes are also made of plankton debris, but these organisms build their shells using silica or hydrated silica. In some cases such as with diatomaceous earth, sediment is deposited below the calcite compensation depth , a depth where calcite solubility increases. Any calcite -based shells are dissolved , leaving only silica-based shells. Chert is another common rock formed from these types of sediment. These two types of abyssal sediment are also classified as biochemical in origin.
The third sediment type is pelagic clay. Very fine-grained clay particles, typically brown or red, descend through the water column very slowly.
Pelagic clay deposition occurs in areas of remote open ocean, where there is little plankton accumulation. Two notable exceptions to the fine-grained nature of abyssal sediment are submarine fan and turbidite deposits. Submarine fans occur offshore at the base of large river systems. They are initiated during times of low sea level, as strong river currents carve submarine canyons into the continental shelf.
When sea levels rise, sediment accumulates on the shelf typically forming large, fan-shaped floodplains called deltas. Periodically, the sediment is disturbed creating dense slurries that flush down the underwater canyons in large gravity-induced events called turbidites. The submarine fan is formed by a network of turbidites that deposit their sediment loads as the slope decreases, much like what happens above-water at alluvial fans and deltas.
This sudden flushing transports coarser sediment to the ocean floor where they are otherwise uncommon. Turbidites are also the typical origin of graded Bouma sequences. Continental slope deposits are not common in the rock record. The most notable type of continental slope deposits are contourites. Contourites form on the slope between the continental shelf and deep ocean floor. Deep-water ocean currents deposit sediment into smooth drifts of various architectures, sometimes interwoven with turbidites.
The lower shoreface lies below the normal depth of wave agitation, so the sediment is not subject to daily winnowing and deposition. These sediment layers are typically finely laminated, and may contain hummocky cross-stratification. Lower shoreface bed A specific layer of rock with identifiable properties. The upper shoreface contains sediments within the zone of normal wave action, but still submerged below the beach environment.
These sediments usually consist of very well sorted, fine sand. The main sedimentary structure is planar bedding consistent with the lower part of the upper flow regime , but it can also contain cross bedding created by longshore currents.
Transitional environments, more often called shoreline or coastline environments , are zones of complex interactions caused by ocean water hitting land. The sediment preservation potential is very high in these environments because deposition often occurs on the continental shelf and underwater.
Shoreline environments are an important source of hydrocarbon deposits petroleum , natural gas. The study of shoreline depositional environments is called sequence stratigraphy.
Sequence stratigraphy examines depositional changes and 3D architectures associated with rising and falling sea levels, which is the main force at work in shoreline deposits. These sea-level fluctuations come from the daily tides, as well as climate changes and plate tectonics. A steady rise in sea level relative to the shoreline is called transgression. Regression is the opposite, a relative drop in sea level. Some common components of shoreline environments are littoral zones, tidal flats , reef A topographic high found away from the beach in deeper water, but still on the continental shelf.
For a more in-depth look at these environments, see Chapter 12, Coastlines. The littoral zone, better known as the beach, consists of highly weathered, homogeneous, well-sorted sand grains made mostly of quartz.
There are black sand and other types of sand beaches, but they tend to be unique exceptions rather than the rule. Because beach sands, past or present, are so highly evolved, the amount grain weathering can be discerned using the minerals zircon , tourmaline, and rutile.
This tool is called the ZTR zircon , tourmaline, rutile index. The ZTR index is higher in more weathered beaches, because these relatively rare and weather -resistant minerals become concentrated in older beaches.
In some beaches, the ZTR index is so high the sand can be harvested as an economically viable source of these minerals. The beach environment has no sedimentary structures, due to the constant bombardment of wave energy delivered by surf action. Beach sediment is moved around via multiple processes. Some beaches with high sediment supplies develop dune A large pile of sediment, deposited perpendicular to flow.
Tidal flats , or mud flats , are sedimentary environments that are regularly flooded and drained by ocean tides. Tidal flats have large areas of fine-grained sediment but may also contain coarser sands.
Tidal flat deposits typically contain gradational sediments and may include multi-directional ripple marks. Mudcracks are also commonly seen due to the sediment being regularly exposed to air during low tides; the combination of mudcracks and ripple marks is distinctive to tidal flats. Tidal water carries in sediment , sometimes focusing the flow through a narrow opening called a tidal inlet. Tidal channels, creek channels influenced by tides, can also focus tidally-induced flow.
Areas of higher flow like inlets and tidal channels feature coarser grain sizes and larger ripples , which in some cases can develop into dune A large pile of sediment, deposited perpendicular to flow.
Natural buildups of sand or rock can also create reef A topographic high found away from the beach in deeper water, but still on the continental shelf. Geologically speaking, a reef A topographic high found away from the beach in deeper water, but still on the continental shelf.
The term reef A topographic high found away from the beach in deeper water, but still on the continental shelf. Capitol reef A topographic high found away from the beach in deeper water, but still on the continental shelf. Most reef A topographic high found away from the beach in deeper water, but still on the continental shelf. The growth habits of coral reef A topographic high found away from the beach in deeper water, but still on the continental shelf. The hard structures in coral reef A topographic high found away from the beach in deeper water, but still on the continental shelf.
Under certain conditions, when the land beneath a reef A topographic high found away from the beach in deeper water, but still on the continental shelf. Sediment found in coral reef A topographic high found away from the beach in deeper water, but still on the continental shelf.
Water with high levels of silt or clay particles can inhibit the reef A topographic high found away from the beach in deeper water, but still on the continental shelf.
Inorganic reef A topographic high found away from the beach in deeper water, but still on the continental shelf. Examples include the Emperor Seamounts , formed millions of years ago over the Hawaiian Hotspot.
If the reef A topographic high found away from the beach in deeper water, but still on the continental shelf. Lagoons are small bodies of seawater located inland from the shore or isolated by another geographic feature, such as a reef A topographic high found away from the beach in deeper water, but still on the continental shelf. Because they are protected from the action of tides, currents, and waves, lagoon environments typically have very fine grained sediments.
Lagoons , as well as estuaries , are ecosystems with high biological productivity. Rocks from these environments often includes bioturbation marks or coal Former swamp-derived plant material that is part of the rock record.
Around lagoons where evaporation exceeds water inflow, salt flats, also known as sabkhas, and sand dune A large pile of sediment, deposited perpendicular to flow. This is most often seen in marine settings. Deltas form where rivers enter lakes or oceans and are of three basic shapes: river -dominated deltas, wave-dominated deltas, and tide Movements of water rising and falling due to the gravity of the moon and sun. The name delta Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course.
The velocity of water flow is dependent on riverbed slope or gradient , which becomes shallower as the river descends from the mountains. The flow velocity quickly drops as well, and sediment is deposited, from coarse clasts, to fine sand, and mud to form the delta Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course.
As one part of the delta Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course. Deltas are organized by the dominant process that controls their shape: tide Movements of water rising and falling due to the gravity of the moon and sun.
Wave-dominated deltas generally have smooth coastlines and beach-ridges on the land that represent previous shorelines. The Nile River delta Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course.
The Mississippi River delta Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course. Other times the tides or the waves can be a bigger factor, and can reshape the delta Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course.
A tide Movements of water rising and falling due to the gravity of the moon and sun. During flood stages when rivers have lots of water available, it develops distributaries that are separated by sand bars and sand ridges. The tidal delta Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course.
Terrestrial depositional environments are diverse. Water is a major factor in these environments, in liquid or frozen states, or even when it is lacking arid conditions. Fluvial river systems are formed by water flowing in channels over the land.
They generally come in two main varieties: meandering or braided. In meandering streams , the flow carries sediment grains via a single channel that wanders back and forth across the floodplain.
The floodplain sediment away from the channel is mostly fine grained material that only gets deposited during floods. Braided fluvial systems generally contain coarser sediment grains, and form a complicated series of intertwined channels that flow around gravel and sand bars see Chapter 11, Water.
A distinctive characteristic of alluvial systems is the intermittent flow of water. Alluvial deposits are common in arid places with little soil A type of non-eroded sediment mixed with organic matter, used by plants. Lithified alluvial bed A specific layer of rock with identifiable properties. The most distinctive alluvial sedimentary deposit is the alluvial fan, a large cone of sediment formed by streams flowing out of dry mountain valleys into a wider and more open dry area. Alluvial sediments are typically poorly sorted and coarse grained, and often found near playa lakes or aeolian deposits see Chapter 13, Deserts.
Lake systems and deposits, called lacustrine , form via processes somewhat similar to marine deposits, but on a much smaller scale. Lacustrine deposits are found in lakes in a wide variety of locations. Lake Baikal in southeast Siberia Russia is in a tectonic basin. Crater Lake Oregon sits in a volcanic caldera. The Great Lakes northern United States came from glacially carved and deposited sediment. Ancient Lake Bonneville Utah formed in a pluvial setting that during a climate that was relatively wetter and cooler than that of modern Utah.
Oxbow lakes, named for their curved shape, originated in fluvial floodplains. Lacustrine sediment tends to be very fine grained and thinly laminated, with only minor contributions from wind-blown, current, and tidal deposits. When lakes dry out or evaporation outpaces precipitation , playas form. Playa deposits resemble those of normal lake deposits but contain more evaporite minerals. Certain tidal flats can have playa -type deposits as well.
Paludal systems include bogs, marshes, swamps, or other wetlands, and usually contain lots of organic matter. Paludal systems typically develop in coastal environments, but are common occur in humid, low-lying, low- latitude , warm zones with large volumes of flowing water. A characteristic paludal deposit is a peat bog, a deposit rich in organic matter that can be converted into coal Former swamp-derived plant material that is part of the rock record.
Since wind has a much lower carrying capacity than water, aeolian deposits typically consists of clast sizes from fine dust to sand. Fine silt and clay can cross very long distances, even entire oceans suspended in air. With sufficient sediment influx, aeolian systems can potentially form large dune A large pile of sediment, deposited perpendicular to flow.
The figure shows dune A large pile of sediment, deposited perpendicular to flow. British geologist Ralph A. Bagnold considered only Barchan and linear Seif dune A large pile of sediment, deposited perpendicular to flow.
Other scientists recognize transverse, star, parabolic, and linear dune types. Parabolic and linear dunes grow from sand anchored by plants and are common in coastal areas. Compacted layers of wind-blown sediment is known as loess. Loess commonly starts as finely ground up rock flour created by glaciers. Such deposits cover thousands of square miles in the Midwestern United States.
Loess may also form in desert regions see Chapter Glacial sedimentation is very diverse, and generally consists of the most poorly-sorted sediment deposits found in nature. Organic weathering happens when plants break up rocks with their growing roots or plant acids help dissolve rock. Once the rock has been weakened and broken up by weathering it is ready for erosion.
Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity. Mechanical weathering physically breaks up rock. One example is called frost action or frost shattering.
Water gets into cracks and joints in bedrock. When the water freezes it expands and the cracks are opened a little wider.
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