Geography

Cyanobacteria

Cyanobacteria

Cyanobacteria Definition Cyanobacteria are any of a phylum of photosynthetic bacteria that live in water or damp soil and were once thought to be plants. The name “cyanobacteria” comes from the color of the bacteria (Greek: κυανός (kyanós) = blue). Cyanobacteria (which are prok.....

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Stromatolite

Stromatolite

Stromatolite Definition Stromatolite is a dome-shaped structure consisting of alternating layers of carbonate or silicate sediment and fossilized algal mats. Stromatolites are one of the oldest fossils known, some dating to over 3.5 billion years old. Stromatolites are produced over geologic time.....

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Porphyry

Porphyry

Porphyry Definition Porphyry is an igneous rock containing the large crystals known as phenocrysts embedded in a fine-grained matrix. The larger crystals are called phenocrysts. In its non-geologic, traditional use, the term porphyry refers to the purple-red form of this stone, valued for its app.....

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St Martin’s Island

St Martin’s Island

St Martin’s Island St Martin’s Island is a small island in the northeast of the bay of bengal, about 9 km south of the Cox’s Bazar-Teknaf peninsular tip and forming the southernmost part of Bangladesh. South along the coast from Cox’s Bazar, St Martin’s Island is Banglad.....

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Craton

Craton

Craton Definition Craton is a large portion of a continental plate that has been relatively undisturbed since the Precambrian era and includes both shield and platform layers. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tecton.....

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Plate Tectonics

Plate Tectonics

Plate Tectonics Definition Plate tectonics is a theory that the Earth’s lithosphere (the crust and upper mantle) is divided into a number of large, platelike sections that move as distinct masses. The movement of the plates is believed to result from the presence of large convection cells i.....

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Earthquake

Earthquake

Earthquake Definition Earthquake is a sudden movement of the Earth’s lithosphere (its crust and upper mantle). Earthquakes are caused by the release of built-up stress within rocks along geologic faults or by the movement of magma in volcanic areas. They are usually followed by aftershocks......

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Seismic Wave

Seismic Wave

Seismic Wave Definition Seismic wave is an elastic shock wave that travels through the earth, as from an earthquake or explosion; also, one of four distinct waves generated by an earthquake. Earthquakes generate four principal types of elastic waves; two, known as body waves, travel within the Ea.....

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Continental Crust

Continental Crust

Continental Crust Definition Continental crust is the solid, outermost layer of the Earth, lying above the mantle.  This layer is sometimes called sial because its bulk composition is more felsic compared to the oceanic crust, called sima which has a more mafic bulk composition. The crust that i.....

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Metamorphism

Metamorphism

Metamorphism Definition Metamorphism is the process by which rocks are changed in composition, texture, or structure by extreme heat and pressure. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. The chemical components and crystal structures of.....

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Metasomatism

Metasomatism

Metasomatism Definition Metasomatism is the process by which the chemical composition of a rock is changed through the introduction or extraction of chemicals dissolved in fluids that migrate through the rock’s pores. Metasomatism often results in the formation of new minerals, especially m.....

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Permafrost and its Effects

Permafrost and its Effects

What is Permafrost? Permafrost is a thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in Polar Regions. It is defined as ground (soil or rock and included ice or organic material) that remains at or below 0°C for at least two consecutive years. Lowland per.....

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