name the three stages of lithification of sedimentary rocks
Answers
❕❕ANSWER❕❕
THE THREE STATES OF LITHIFICATION OF SEDIMENTARY ROCKS ARE:
♧ EVAPORATION
◇COMPACTION
♡CEMENTATION
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Answer:
Sedimentary Rocks
Igneous rocks are sometimes considered primary rocks because they crystallize from a liquid. In that case, sedimentary rocks are derived rocks because they are formed from fragments of pre-existing rocks.
Formation of Sedimentary Rocks
Sedimentary rocks are the product of 1) weathering of preexisting rocks, 2) transport of the weathering products, 3) deposition of the material, followed by 4) compaction, and 5) cementation of the sediment to form a rock. The latter two steps are called lithification.
Weathering
When rocks (igneous, sedimentary, or metamorphic) are at or near the surface of the earth they are exposed to the processes of weathering.
In mechanical weathering rocks are broken up into smaller pieces by frost-wedging (the freezing and thawing of water inside cracks in the rock), root-wedging (tree and other plant roots growing into cracks), and abrasion caused by, for example, sand-blasting of a cliff face by blowing sands in the dessert, or the scouring of water transported sand, gravel, and boulders on the bedrock of a mountain stream. Mechanical weathering breaks rocks into smaller and smaller pieces but without otherwise altering the minerals.
In chemical weathering minerals are changed into new minerals and mineral byproducts. Some minerals like halite and calcite may dissolve completely. Others, especially silicate minerals, are altered by a chemical process called hydrolysis. Hydrolysis is the reaction of minerals in weakly acidic waters. Most natural surface waters are slightly acidic because carbon dioxide from the air dissolves in the water. Some of the dissolved CO2 reacts with the water forming the chemical compound carbonic acid.
Complete weathering of silicate rocks will yield:
solid materials
1) clays
2) quartz sand (if the rock originally contained quartz)
dissolved materials
3) soluble silica
4) metal cations
Rock fragments will also remain where the rocks are not completely weathered.
Not only is quartz the most stable of the common rock forming minerals in chemical weathering, its high hardness and lack of cleavage make it quite resistant to mechanical weathering. Quartz is itself an agent of mechanical weathering in the form of blowing dessert sand.
more on weathering
Transport
As the process of weathering proceeds the products are carried off. The most important transporting agent is water. Water carries or rolls particles in rivers, from the smallest suspended clay particles to the largest boulders. Boulders and smaller rock fragments continue to be broken up and chemically altered as they tumble downstream. Water also carries dissolved minerals, such as silica and cations downstream as well as in the groundwater. Other transporting agents include wind which blows dust and sand, glaciers, which carry large amounts of gravel and huge boulders in addition to smaller particles, and mass wasting on hillslopes. In addition to decreasing the particle size, as sedimentary material is transported it is also sorted into similar sized particles as a result of changing energy (velocity) in the transporting medium (water or wind), and rounded by continued abrasion.
Deposition
Sediments are transported only when there is enough energy in the transporting medium, for example, when a stream is flowing rapidly enough to carry a given size of sedimentary particle. Steep mountain streams can move large boulders during spring flood but these boulders will never be transported out into a placid lowland river. So the largest sediments (boulders, cobbles, and pebbles) which survive the weathering process, tend to be deposited near to their source, for example at the point where a mountain stream flows out onto a valley floor. Sediments of a given size are deposited whenever they move into an environment with insufficient energy to transport them. For example, silt carried by a flooding river will settle out in the quiet backwaters outside the river banks (perhaps enriching someone's farmland - while wrecking their home).
Sediments are deposited layer upon layer. The layers are deposited horizontally.
Sorting. When a river encounters the ocean it begins to deposit its suspended sediments. Progressively finer sediments are deposited moving away from the shoreline. All fine materials are winnowed out leaving sands in the wave-dominated beach and nearshore environment. The sands remain in this high energy environment. In deeper/calmer water silt settles out. In water deep enough not to be affected by surface wave action the clay fraction begins to settle out.
The dissolved load in water will precipitate out (crystallize) if it encounters a supersaturated environment. Gypsum, halite, and other salts, precipitate out of seawater in arid areas, like the eastern Mediterranean, where evaporation is high (thus increasing the salinity) and influx of fresh seawater is low.