Zygote

the cell produced by the fusion of male and female germ cells (GAMETES) during the initial stage of FERTILIZATION. The zygote is a DIPLOID cell, formed by the fusion of the haploid male gamete and the haploid female gamete.

Taken from Dictionary of Science

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A zygote (from Greek ζυγωτός zygōtos "joined" or "yoked", from ζυγοῦν zygoun "to join" or "to yoke"), or zygocyte, is the initial cell formed when a new organism is produced by means of sexual reproduction. A zygote is synthesized from the union of two gametes, and constitutes the first stage in a unique organism's development. Zygotes are usually produced by a fertilization event between two haploid cells — an ovum from a female and a sperm cell from a male — which combine to form the single diploid cell. Such zygotes contain DNA derived from both the mother and the father, and this provides all the genetic information necessary to form a new individual. The term zygote is also used more loosely to refer to the group of cells formed by the first few cell divisions, although this is properly referred to as a morula.

In mammalian reproduction, after fertilization has taken place the zygote travels down the fallopian tube, while dividing to form more cells without the zygote actually increasing in size. This cell division is mitotic, and is known as cleavage. All mammals go through the zygote stage of life. Zygotes eventually develop into an embryo, and then a fetus. A human zygote exists for about four days, and becomes a blastocyst on the fifth day.

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Unconformity

a break in the deposition of sedimentary rocks, allowing erosion of previously formed rock before eventual deposition of further sediments. It is usually represented by an obvious difference in the attitude of the rocks on either side of the unconformity, with the upper lying unconformably on the lower.

Taken from Dictionary of Science

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An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe any break in the sedimentary geologic record. The phenomenon of angular unconformity (see below) was discovered by James Hutton, who found examples at Jedburgh in 1787 and at Siccar Point in 1788.

The rocks above an unconformity are younger than the rocks beneath (unless the sequence has been overturned). An unconformity represents time during which no sediments were preserved in a region. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not represented is called a hiatus.

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Salt

a compound formed when an ACID reacts with a BASE or when a metal atom replaces one or more hydrogen atoms of an acid. Salts can be formed by other reactions such as two salts reacting together to form different compounds. Salt is also the name given to common salt, or sodium chloride (NaCl), which is found in sea water. It is a vital component of our diet although too much is considered harmful.

Taken from Dictionary of Science

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Salt is a dietary mineral composed primarily of sodium chloride that is essential for animal life, but can be toxic to many land plants. Salt flavor is one of the basic tastes, making salt the oldest, most ubiquitous food seasoning. Salt is also an important preservative.

Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodized salt. It is a crystalline solid, white, pale pink or light gray in color, normally obtained from sea water or rock deposits. Edible rock salts may be slightly grayish in color because of mineral content.

Chloride and sodium ions, the two major components of salt, are necessary for the survival of all known living creatures, including humans. Salt is involved in regulating the water content (fluid balance) of the body. Overconsumption of salt increases the risk of health problems, including high blood pressure.

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Oceanic Crust

the upper part of the oceanic lithosphere down to the MOHOROVICIC DISCONTINUITY. It is formed of several layers commencing with a top layer of sediment which may be thin or absent (as over oceanic ridges). However, near to continental shelves, sediment may accumulate in thicknesses up to 2 or 3 kilometres. Beneath this is a layer of LAVAS (basaltic) and dykes which together are about 2 km thick. The next layer is approximately 5 km (3 miles) thick and its composition is similar to that of gabbro, a coarse-grained basic igneous rock. The base of this layer approaches the MANTLE in composition. These layers seem to remain remarkably constant between ocean basins.

Taken from Dictionary of Science

Igneous Rock

one of the three main rock types that is formed by the forcing up of hot, molten rock (magma), from great depths, or lava flows on the surface associated with volcanoes.

Taken from Dictionary of Science

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Igneous rock (from the Latin ignis meaning born of fire) is one of the three main rock types (the others being sedimentary and metamorphic rock). Igneous rock is formed by magma (molten rock) cooling and becoming solid. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust. These have diverse properties, depending on their composition and how they were formed.

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Xerography

a copying process in which an ELECTROSTATIC image is formed on a surface when exposed to an optical image. A powder mix of GRAPHITE and a thermoplastic resin of opposite charge to the electrostatic image is dusted on to the surface and the particles cling to the charged areas. The image is then transferred to a sheet of paper; again through use of opposite charges, and the image is fixed by heat.

Taken from Dictionary of Science

Water Table

the level below which water saturates the available spaces in the ground. A spring or river is formed when, due to geological conditions, the water table rises above ground level. The position of the water table varies with the amount of rainfall, loss through evaporation and percolation through the soil.

Taken from Dictionary of Science

Obsidian

a volcanic rock which is formed by the rapid cooling of a molten rock with a composition of granite. It is generally glassy, black with a vitreous (glassy) lustre and in composition contains a lot of silica (SiO2).

Taken from Dictionary of Science

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Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools without crystal growth. Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) induces a high viscosity and polymerization degree of the lava. The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth. Because of the lack of crystal structure, obsidian blade edges can reach almost molecular thinness, leading to its ancient use as projectile points, and its modern use as surgical scalpel blades.

Taken from Wikipedia