Category: Geography Notes PPT

Having a chemical formula PbSO4, anglesite mineral is a secondary lead mineral which always occurs through the modification of lead sulfides, principally Galena. Anglesite crystals may consist of impurities of Galena, providing a specimen a gray to black color. In some regions of source, Anglesite occurs as a pseudomorph after Galena, rendering the crystals a false isometric form. Gray and black banding exists in some giant Anglesite specimens that can be observed when a specimen is either sliced or polished.

Angle Site Specimens

Anglesite specimens sliced or polished may even consist of unaltered Galena in the center, which remains constant to Anglesite when the outer layers are changed. An amber-red Anglesite from Morocco has been artificially colored by submerging light yellow crystals in bleach.

Physical Properties of Anglesite

Chemical Properties of Anglesite Mineral

Identifying Characteristics

With a SG of 6.30 to 6.39, the mineral is placed among the densest gem materials. Testing for SG can generally differentiate it from other gems of similar appearance. But, two other rarely faceted collector’s tones consist of a comparable array of colors, hardness, and SG. In the same vein as anglesite, cerussite and phosgenite can also be colorless as well as yellowish, grayish, greenish or white. Their fluorescence under ultraviolet light can also seem to be yellowish.

Although angle sites with pale colors can exhibit high dispersion and brightness, they’re very complicated to cut and not recommendable to wear. Faceted pieces are true rarities, barely spotted except in very exquisite, complete gem collections.

Synthetics

Laboratories have synthesized anglesite for the purpose of geological research. However, there is no apparent use of this substance for jewelry making purposes.

Enhancements

In the early 1980s, amber-red anglesites crystals from Touissit, Morocco were discovered to be an outcome of bleaching colorless and pale yellow specimens. This treatment yielded surface-deep colors. Only submergence in a bromide-water solution is able to reverse this coloration.

Sources of Anglesite Occurrence

Although many localities across the globe can potentially produce gemmy crystals, only a few contain the capacity of yielding colorless and pale brown crystal specimens.

Touissit, Morocco generates gem crystals in massive sizes for this species.

Tsumeb, Namibia yields huge transparent yellowish crystals and, often, gemmy colorless crystal specimens.

Other Notable Gem-Quality Sources are as below:

United States; Arizona; Chester County, Coeur d’Alene district, Idaho; New Mexico; Pennsylvania; Tintic, Utah.

Australia; Wales, Broken Hill, N.S.W., Brazil; Germany; Mexico; Russia; Scotland, Sardinia; Slovenia; Dundas, Tasmania; Tunisia; England, United Kingdom.

Anglesite Stone Sizes

Faceted anglesites essentially range from 1 to 6 carats. Seldom does this substance occur massive enough to cut anything larger than this. However, some rough, remarkably from Morocco and Namibia, has produced 100+ carat gems. One such stone from Tsumeb, notably of 300 carats, broke during cutting!

Care of Anglesite Crystal

Anglesites majorly consist of lead. When cutting this mineral, avoid ingesting or inhaling splinters and make sure to wash your hands. Jewelry use is not advisable. 

Anglesite Uses

Some Uses of Anglesite Mineral are in:

Fun Facts

• Anglesite is a lead mineral, quite rare in occurrence.

• It contains bladed or tabular crystals, having a mohs hardness of 2.5-3 and SG of 6.3.

• It is a secondary mineral, essentially occurring in the oxidation zone of a lead sulfide.

• This anglesite mineral contained several lead crystals on its surface.

• The mineral is associated with galena, barite, cerussite, and liminote

• Anglesite crystal is named for its type locality at the Parys Mine, on the Island of Anglesey, Wales (UK).

• Pbso4 mineral can also be found in black color due to Galena impurities, which can also induce it to be banded gray and black.

• Where it occurs massively, it caters as a lead ore.

• Anglesite’s fire or dispersion is equivalent to that of diamond (0.044).

• If properly faceted, this crystal can also exhibit magnificent brilliance.

• Due to angelsite’s hardness of 2.5 to 3 and good cleavage, cutting demands great care.

Batholith comes from Greek culture. Batho means depth, and litho is rock. So, batholith is a large mass of intrusive igneous rock that can be as large as 100 square km. Usually, these rocks are a formation of cooled magma deep in the Earth’s crust. The maximum of batholiths is made of felsic or intermediate rock types like quartz monzonite, granite, or diorite.

Process of Formation of Batholith Rock

The formation of batholith rocks involves complex compositions and histories though they appear uniform. Multiple masses or plutons are bodies of igneous rocks of irregular dimensions (several km) that can be identified by some criteria like age, texture, composition, or mappable structures. Magma travel from the zone of partial melting towards the Earth’s crust that forms solid individual plutons.

These plutons arise from large masses called plutonic diapirs. The diapirs are hot and liquefied and hence can burst through surrounding rocks, pushing them aside and going through partial melting. Based on their force, they settle just below the ground at about 5 to 30 km instead of bursting above the surface like a volcano. Therefore they are mentioned as plutons (Roman god of underworld Pluto). The other consideration about plutons is that they are not evolved from larger magma diapirs but from aggressive smaller volumes of magma that rise like dikes.

When many plutons come up together, they form a huge granitic rock. Some batholiths are spread over hundreds of kilometers in the continental crust. Sierra Nevada Batholith is an example of such batholiths. It covers most parts of the Sierra Nevada in California. A bigger batholith than this is the Coast Plutonic Complex that is mostly found in the Coast Mountains of Western Canada. It is known to be spread about 1800 km and reaches up to southeastern Alaska. 

Erosion and Geology: 

Continuous plutonic rocks that cover an area of 100 sq km or more than that are called batholith, whereas those with an area less than 100 sq km are called stocks. However, most of the visible batholiths on the surface are spread on far more than 100 sq km area. The continental uplift of the erosion process working from ages acts upon these areas to expose them. Over many years, several tens of sq km of overlying rocks are removed in many areas. 

The result of a big pressure difference when the batholiths were down underground and when they are exposed on the surface is little expansion of their crystal structure. This leads them to form a mass wasting called exfoliation. This tends to rocks becoming convex and thin sheets of rocks to slough off the exposed surfaces. The rock faces become clean and rounded. An example of this is Half Dome in Yosemite Valley. 

From the Batholith Diagram, we can understand it thoroughly. 

Batholith and Laccolith:

We have learned about batholiths till now. We will now discuss laccolith. A laccolith is a type of rock that appears with sheet-like intrusions which are injected within the layers of sedimentary rocks. This is the result of the movement of strata of the sedimentary rock upward or makes them fold when the magma pressure is high enough. This is the reason why laccoliths appear dome shape or mushroom-like with a plain base. 

Erosion of these rocks makes small hills, a central peak, or a mountain. Magma rocks are highly weather-resistant. The formation of laccolith is usually quicker.

Difference Between Batholith and Laccolith:

A large mass of igneous rock forms a batholith, while laccolith is sheet-like intrusions injected within the layers of sedimentary rocks. 

Batholith occurs as individual igneous intrusive rock, while laccolith occurs as an intrusion in sedimentary rocks.

Batholiths form when many plutons get together to form a granitic rock, and laccolith forms when high-pressure magma move the strata of sedimentary rocks.

The batholith is a large irregular mass of intrusive igneous rocks that forces themselves in surrounding strata, and laccolith is a mass of igneous or volcanic rock within strata.

Batholith and laccoliths are part of igneous rocks and volcanic landforms. There are many other features, some of which we can quickly review –

Lava Flow: They are streams of extremely hot lava pouring out of a volcanic vent or fissure. Sometimes the flow pressure may be so high that it can erupt high in the air and flow in surrounding areas melting everything in its way.

Fissure: A fissure can be a long crack on Earth’s surface through which the lava erupts out. This is called a fissure eruption. 

Volcanic Neck: This landform occurs when the magma solidifies inside a conduit leading to a volcano vent. Softer rocks get eroded, but this being stronger, it stands above the surface. 

Volcanic Cone: These are steep-sided hills or mountains built with layers of erupted lava flows. It is cone-shaped and usually light or dark-coloured.

Volcanic Pipe: It is a pipe-type outlet for lava eruption when the surrounding underground surface is too hard. This will be weaker and hence allow lava to get pushed up. After the process, it becomes a solidified magma of a hard, cylindrical shape.

A cenote is a natural pit or sinkhole formed when limestone bedrock collapses, exposing groundwater. Cenotes have been generally used for water sources by the ancient Maya, and sometimes for sacrificial sacrifices, in the Yucatán Peninsula of Mexico. Similar rock-sided sinkholes, such as cenotes, being common geological types in low-altitude areas, especially on coastlines, islands, and platforms with young post-Paleozoic limestones with less soil growth. Similar karst characteristics in several other countries, including Cuba and Australia, have been referred to as cenotes.

Here is the List of Notable Cenotes: 

• Gran Cenote, 

• Cenote Suytun, 

• Cenote Zaci, 

• Cenote Angelita, 

• Cenote Hubiku, 

• Cenote Oxman, 

• Cenote Maya And 

• Cenote Samula.

Geology and Hydrology

Cenotes are created by rock dissolution and also the subsequent structural collapse of a subsurface void, that might or might not be connected to an active cave system. Additional dissolution slowly removes rock that drops into the water underneath, making room for even more collapse blocks.

Because the rock ceiling is no more buoyantly protected by the water in the void, the level of collapse is able to intensify whenever the water table is under the void’s ceiling. Cenotes can be completely collapsed, resulting in an open water pool, or severely damaged, with certain rocks overhanging well above water. Cenotes are frequently compared to small circular ponds with sheer rock walls, stretching tens of metres in diameter. Many cenotes, on the other hand, need some stooping or crawling to get to the water.

Penetration and Extent

The gran cenote in Mexico’s Yucatán Peninsula’s north and northwest overlie vertical voids that reach 50 to 100 metres (160 to 330 feet) below the modern water table. Nevertheless, several of these cenotes tend to be related to horizontally vast underground river systems, with aquifer matrix and fracture streams possibly dominating water flow via them. 

Cenotes across the Yucatán Peninsula’s Caribbean coast (throughout the state of Quintana Roo) frequently provide access to vast underwater cave systems, including Sistema Ox Bel Ha, Sistema Dos Ojos and Sistema Sac Actun/Sistema Nohoch Nah Chich.

Freshwater/Seawater Interface

The Yucatán Peninsula has a large coastal aquifer system that is usually stratified by density. The infiltrating meteoric water (that is, rainwater) floats on the surface of the saline water intruding from the coastal margins, which has a greater density. As a result, the entire aquifer seems to be an anchialine system (one of which is land-locked, however, is connected to an ocean).

The interface between fresh and saltwater can be achieved where a cenote, or the submerged cave to which this is an opening, offers shallow enough entry into the aquifer. A halocline seems to be a sharp change in salt concentration beyond a slight change in depth there at the density interface amongst fresh and salty waters. The refraction between the various densities of fresh and salty waters causes a distorted swirling effect when fresh and saline water are mixed.

Climate, precisely how much meteoric water charges up the aquifer, hydraulic conductivity of the host rock, accessibility and distribution of established cave systems, as well as how efficient these are at draining water to the shore, as well as the distance from the coast, all influence the extent of the halocline.

The halocline is lower farther away from the shore, and in the Yucatán Peninsula, such depth is 10 to 20 m (33 to 66 ft) underneath the water table at the coast, as well as 50 to 100 m (160 to 330 ft) far below the water table in the centre, with saltwater covering the entire peninsula.

Types: Cenotes were first classified using a basic morphometry-based classification scheme in 1936.

• Cenotes-cántaro (Jug or pit cenotes) have a surface relation that is narrower than the water body’s diameter.

• Cenotes-cilndricos (Cylinder cenotes) have walls that are completely vertical.

• Cenotes-aguadas (Basin cenotes) have shallow water basins, and 

• Grutas (Cave cenotes) have a horizontal gateway and dry areas.

Since the classification scheme is dependent on morphometric observations well above the water table, it only partially represents the mechanisms by which cenotes evolved and also the inherent hydrogeochemical relationship with the corresponding flooded cave networks, that were only identified in the 1980s and subsequently with the start of cave diving exploration.

Flora and Fauna

Although flora and fauna are usually scarcer throughout caves than those in the open ocean, marine animals still thrive there. Mojarras, guppies, mollies, small eels, catfish, and frogs could all be found in caverns. The fauna has developed to mimic that of several Cave-Dwelling animals in the most secluded and deeper cenotes.

Numerous animals, for particular, lack pigmentation and are sometimes blind, thus they have large feelers to locate food and navigate in the dark.

Chicxulub Crater

While cenote suytun can be found all over the Yucatán Peninsula, the estimated rim of the Chicxulub crater is overlain by a higher-density circular alignment of cenotes.

This crater formation, which was discovered by the alignment of cenotes but later mapped utilizing geophysical methods (such as gravity mapping) and drilled into this with core recovery, has also been dated to the 66 million-year-old Cretaceous-Paleogene geologic boundary. As a result of the meteorite impact at the Cretaceous–Paleogene boundary, the mass extinction of dinosaurs is regarded as the Cretaceous–Paleogene extinction event.

Scuba Diving

Cenotes frequently attracted cavern and cave divers, and attempts to investigate and map such underwater structures have been coordinated. They are either public or private, and are occasionally referred to as “National Natural Parks.” When swimming, extreme caution should be exercised to avoid destroying this delicate ecosystem.

The Quintana Roo Speleological Survey in Mexico keeps a record of the state’s deepest and longest water-filled and dry caves. When caving, one ought to be enabled to see natural light for the duration of the cavern exploration (for example, Kukulkan cenote near Tulum, Mexico). Throughout a cave dive, one crosses the point whereby daylight will enter the cave and exits by following a protection guideline. When you transition from a cavern dive to a cave dive, things change drastically. So many more divers, including the most seasoned, have died as a result of disregarding safety precautions. 

Cenote cave diving, unlike cenote cavern diving, necessitates specialised equipment and preparation (certification for cave diving). Both cavern and cave diving, on the other hand, necessitate thorough briefings, prior diving experience, and weight adjustment to freshwater buoyancy. Typically, the cenotes are loaded with cold, freshwater. Cenote divers have to be cautious of the potential halocline, which causes vision to blur until they enter a much more homogeneous region.

Conclusion

A cenote is a natural pit or sinkhole created by the collapse of limestone bedrock, exposing groundwater. Cenotes were used by the ancient Maya in the Yucatán Peninsula of Mexico as water sources and sometimes for sacrificial sacrifices. Cenotes are formed by the dissolution of rock and the resulting structural collapse of a subsurface void, which may or may not be linked to an active cave system. Additional dissolution gradually eliminates rock that falls into the water underneath, allowing further collapse blocks to be added.

Coastal landforms are any of the relief features which are there along any coast.  This is the result of the combination of processes, sediments, and also the geological structure on the coast itself. 

The coastal environment of the world is processed with a wide variety of landforms that are manifested in a spectrum of sizes and different shapes which ranges from the gently sloping beaches to the high towering cliffs. The coastal landforms are best considering the two broad categories: erosional and depositional. 

Name Some Coastal Landforms

The different types of Coastal Landforms are as follows:

Among the Erosional Coastal landform types:

Sea Cliffs 

These are the most widespread landforms which are formed due to the erosional coasts. The coastal landforms range from very steep to vertical bedrock cliffs which are only a few metres high to hundreds of metres above sea level. 

Wave Cut Platform 

At the base of most cliffs also along the rocky coast, one can find a flat structure on the mid-tide elevation. This structure is like a benchlike feature which is called a wave-cut platform. These surfaces may range from a few metres to hundreds of metres wide.

Sea Stacks

Erosion which might occur along the rocky coasts at various rates is dependent both on the rock type and on the wave energy at this particular site.

Sea Arches

Yet another spectacular type of erosional landform is this sea arch, which forms as the result of different rates of erosion generally because of the varied resistance of bedrock. 

Marine Landforms 

To understand Marine Landform, we can study the various points:

• The sea waves are aided by the winds, by the currents, and the tides. The storms carry on the erosional and depositional processes to form these landforms.

• The erosion process at the sea depends upon the size and the strength of the waves, slope, height of the shore which is between the low and the high tides, and the shape of the coast, the composition of rocks, depth of the water, human activity etc.

• The wave pressure compresses in the air that is trapped inside the rock fissures, joints, faults, etc. which, in turn, forces the air to expand and to rupture and break the rocks at their weak points. 

• Waves also use rock debris as a means of erosion. These rock fragments that are carried between the waves themselves get worn down.

• The solvent or the chemical action of these waves is another mode of erosion process. 

Coastal Features

The coast is the strip of land that meets an ocean or the sea. Coasts have many different features like caves and cliffs, beaches and mudflats. The Tides, waves, and water currents shape the land to form the coastal features.

 

Coastal Depositional Landforms 

The landforms of the Coastal Deposition occur when the sea drops or deposits the material. This phenomenon includes sand, sediment and the shingle which results in the formation of landforms of coastal deposition.

Coastal Processes and Landforms 

The landforms which develop and stay along the coast are the result of a combination of the processes which acts upon the sediments and the rocks that are present in the coastal zone. Among the most prominent of these processes involves the waves and the currents which are being generated along with the tides.

Features of Coastal Deposition 

Features of coastal deposition are the features of deposition that are found in the coastal areas between the high and low tide. This is normally found in those areas where there is an inlet or a sheltered area, between the headlands or a change in the coastline that causes the sediment to be trapped and to build up.

Beach Landform

The beach is the general that area is between the lowest spring tide level and between the point reached by the storm waves in the highest tides. Every other beach is different but all are usually made up of material that is deposited on the wave-cut platform. These beaches are formed from sand, sand and the shingle, also known as the pebbles. They also can be formed from the processing of the mud and silt.

A crystalline rock is a rock composed entirely of crystallized minerals without any glassy matter. Intrusive igneous rocks, especially the ones that turn semi-solid on cooling at the depth are always observed to be crystalline whereas extrusive igneous rocks are mostly non-crystalline rocks as they can be partly or fully glassy. Another type of rock that is mostly crystalline is metamorphic rock. The metamorphic rocks are known to be subjected to high temperatures and pressures which aids in the crystallization processes of their mineral content. Thus, in general, two types of rocks form crystalline rocks which are: crystalline igneous rocks and crystalline metamorphic rocks.

Detail Description of Crystalline Rock:

Crystalline rock means any rock composed entirely of crystallized minerals without glassy matter. Intrusive igneous rocks are those that congeal at depth and are virtually always crystalline, whereas extrusive igneous rocks, or volcanic rocks, may be partly to entirely glassy. Many factors affect the crystallization capacity of magma, but the length of time it takes to cool is the decisive factor. Metamorphic rocks are mostly crystalline. The term crystalline shale has been used to describe all rocks of metamorphic origin, so the term crystalline rock can be understood to be of igneous origin. Sedimentary rocks are also  crystalline, like crystalline limestone that precipitates directly from solution. Debris deposits are formed primarily from the accumulation of crystalline material, but the term is not commonly used for debris deposits.

Salient Features of Crystalline Rock:

• Crystalline rocks, particularly granitic rocks, and basalts, are one of the principal rock types under consideration as the potential host rocks for a high-level radioactive waste repository.

• Rocks with crystalline texture are usually harder and more compact than those with a granular texture. When crystalline rocks are broken they tend to fracture along smooth, angular surfaces within individual crystals, rather than between crystals.

• Crystalline textures include phaneritic, foliated, and porphyritic. Phaneritic textures are where interlocking crystals of igneous rock are visible to the unaided eye. The foliated texture is where metamorphic rock is made of layers of materials. Fragmental textures include clastic, bioclastic, and pyroclastic.

Formation:

Crystalline rocks are formed because of the polymerization of minerals. The Crystalline rocks are called so because of the excess of crystals that are present in them and also because of the highly organized microscopic structures of these crystals for which the highly tensed geological processes are responsible.

Brief Description of Rocks

There are many different types of rocks found in the crust of the Earth. Typically a rock is formed under different conditions that occur due to geological processes and is a mixture of one or more minerals. These conditions and the contents provide a rock with soft or hard physical properties. Such variation is observed in-between granite and soapstone as the granite is hard and the soapstone is soft. Other differences in properties or rocks are shown by gabbro which is black in color and quartzite which is white. Also, these properties are sometimes defined by the mineral contents. Although rocks might not contain minerals in a definite composition the most common minerals are feldspar and quartz.

As said previously there are many different types of rocks present in the Earth’s crust.

They are mainly classified into three types based on their mode of formation.

These Three Rocks along with their Formation Process are Listed below:

1. Igneous Rocks: These types of rocks are formed by the solidification of magma and lava. Examples include granite, gabbro, pegmatite, basalt, etc.

2. Sedimentary Rocks: These are formed by the deposition of fragments of rocks that were subjected to exogenous processes. Examples of these types are limestone, coal, halite, potash, etc.

3. Metamorphic Rocks: These are the types of rocks that are formed from the existing rocks which are undergoing recrystallization. Granite, gneiss, slate, schist, marble, etc are examples of metamorphic rocks.

Out of the above three mentioned types of rocks, the rocks that fulfill crystalline rock meaning are igneous rock and metamorphic rock and the non-crystalline rocks include the sedimentary rocks. This is mainly because both these types of rocks undergo processes that involve high temperature, high pressure, and higher stress with the changing geological conditions that help in the process of crystallization especially of the mineral content contained within these rocks. As mentioned the prime examples of crystalline igneous rocks include granite, and gabbro whereas the examples of crystalline metamorphic rocks include the gneiss and the schist which is a black crystalline rock. Although limestones are primarily sedimentary rocks, there are also crystalline limestone rock/limestone crystalline rocks that are part of certain metamorphic rocks. Another significant example of crystalline rocks includes the Precambrian crystalline rocks that are hard crystalline rocks which along with high-grade metamorphic rocks formed tectonically stable areas.

More about the Salient Features of Crystalline Rocks

The crystalline rock meaning is a salient feature of the physical characteristics of igneous rock and a metamorphic rock mainly because of its mineral composition. Crystalline rocks are formed because of the polymerization of minerals. Crystalline rocks are so-called because of the excess of crystals that are present in them and also because of the highly organized microscopic structures of these crystals for which the highly tensed geological processes are responsible. The environment of crystalline igneous rocks or crystalline metamorphic rocks is composed of many igneous and metamorphic rocks.

The compositions and the physical properties of igneous rocks are known to be mostly controlled by the crystallization history of the rock. Some types of igneous rocks like the ultramafic rocks contain mineral assemblages that typically crystallize at higher temperatures than felsic (another classification of igneous rocks) rocks. They contain mineral phases of different groups such as iron-magnesium-calcium silicates, etc. indicating that any interaction between the fluids found in this crystalline environment is an interaction between minerals and the fluid is the same as fluid and rock.

A crystalline rock can either be classified as batholiths which have a dominant composition of granite rock with somewhat metamorphic characteristics of metamorphic rocks with very few granitic instructions. Images, as described, Joseph A. Dipietro in Geology and Landscape Evolution (Second Edition), 2018,  of such a classification of rocks is shown below:

Eluviation meaning is the downward percolation of water through soil horizons that transports soil content from upper layers to lower levels, and illuviation is the deposition of this material (illuvial deposit) in lower levels. Eluviation is the movement of water that removes dissolved or suspended material from a layer or layers of soil when rainfall exceeds evaporation. Leaching is the term used to describe the loss of material in the solution.

Eluviation Definition

The transportation of dissolved or suspended material within the soil by the movement of water as rainfall exceeds evaporation.

Eluvium or alluvial deposits are volcanic deposits and soils formed by in situ weathering or weathering combined with gravitational movement or deposition in geology.

Eluviation or leaching is the method of removing materials from geological or soil horizons. There is a distinction between how this word is used in geology and soil science. Eluviation is the downward percolation of water through soil horizons that transports soil content from upper layers to lower levels, and illuviation is the deposition of this material (illuvial deposit) in lower levels. The extracted material is meaningless in geology, and the deposit (alluvial deposit) is the material that remains. When precipitation exceeds evaporation, eluviation occurs.

An alluvial zone or illuvial horizon is a soil horizon created by eluviation. The illuvial horizon is a light-colored region in a standard soil profile that is either at the lower part of the A horizon or within a distinct horizon (E horizon) below the A, where the process is most strong and rapid (depending on background and literature). While eluviation theoretically occurs in both, some sources consider the alluvial zone to be the A horizon plus the (distinct) E horizon. The strict illuvial horizon (E horizon) is usually light grey, clay-free, low in organic matter, and high in salt and sand particles made up of quartz and other resistant minerals.

Alluvial ore deposits, including tungsten and gold placer deposits, are created by settling and enriched by winnowing or removing lower-density materials. Alluvial deposits are diamonds found within the yellow ground (weathered parts of kimberlites). Residual or alluvial deposits of cassiterite and columbite-tantalite can also be found. The Pitinga tin deposit, an alluvial deposit in Brazil, is one of the world’s largest tin mines. In Ontario, weathering supergene enrichment of an apatite-rich carbonatite has resulted in a large alluvial phosphate ore deposit.

Eluviation of Soil

Water pushes tiny colloidal-sized materials into the soil as it moves through it. Eluviation is the movement or leaching of materials such as clay, iron, or calcium carbonate. The region of eluviation, also known as the E horizon or eluviation layer of soil, is the area where the materials have been extracted. Alluvial zones have fewer nutrients for plant growth. In forested soils, E horizons are common.

Different forms of soil exist, each with its own set of characteristics. Any soil has layers, or horizons, as you can see if you dig far enough (O, A, E, B, C, R). When you combine the horizons, you get a soil profile. Each profile, like a biography, tells a tale about a soil’s life. Most soils have three main horizons (A, B, and C), as well as an organic horizon in some cases (O). The following are the horizons:

O (Humus or Organic): Organic matter, primarily decomposing leaves. Some soils have a thin O horizon, while others have a dense O horizon or none at all.

A (Topsoil): Mostly minerals from the parent material, with some organic matter. Plants and other organisms can thrive in this material.

E (Eluviate): Leached of clay, minerals, and organic matter, leaving a concentration of sand and silt particles of quartz or other resistant materials – contained in older soils and forest soils. 

B (Subsoil): Minerals leached (moved down) from the A or E horizons and deposited in the B.

C (Parent Material): The deposit that formed the soil at the Earth’s surface.

R (Bedrock): A mass of rock, such as granite, basalt, quartzite, limestone, or sandstone, that serves as the parent material for some soils when it is close enough to weather. This isn’t dirt, because it’s under the C horizon.

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