igneous rock

a rock that has solidified form molten rock material (magma) which was generated deep within the Earth. Igneous rocks are one of the three main groups of rocks that comprise the Earth's crust ( the others being sedimentary and metamorphic).



a black or dark brown rhombohedral mineral FeTiO3, a major ore of titanium; it occurs in compact or granular aggregates.



intrusion, also called injection, is the emplacement of magma into pre-existing rock. It can take place either by deformation of the involved rock, or along some structural channels such as bedding planes, cleavages or joints.



a porphyritic, ultrabasic intrusive igneous rock containing abundant olivine and mica of the phlogopite variety in a serpentine and carbonate-rich matrix. Host rock of diamond.



molten rock (or magma) that issues from openings at the Earth's surface or on the ocean floor. Such openings may be located in craters or along flanks of volcanoes, or in fissures not associated with volcanic cones.



a sedimentary rock composed almost entirely of calcium carbonate mainly as the mineral calcite. Organic limestones consist of shell remnants or of calcite deposits precipitated by certain algae, e.g. coral limestone, crinoidal limestone, chalk. Chemically precipitated limestones form mainly in warm shallow seas.



Lystrosaurus lived in Africa, India and China 200 million years ago. The discovery in the 1960's of a fossil of Lystrosaurus in Antarctica was evidence to support the idea of continental drift.



molten, mobile rock material that is a naturally occurring high temperature solution of silicates, water and gases. Suspended solids such as crystals and rock fragments may or may not be included. Magmas is generated deep within the Earth's crust or upper mantle as a result of partial melting, and is the sources of igneous rocks.



large quadrupedal, herbivorous sauropod dinosaur from Triassic rocks, specifically the Elliot Formation of South Africa.



having undergone metamorphism - the processes which produce structural and mineralogical changes in any type of rock in response to physical and chemical conditions differing from those under which the rocks originally formed. Changes brought about by near-surface processes such as diagenesis and weathering are excluded.



commonly used synonym for mudrock, a fine-grained sedimentary rock composed chiefly of particles in the silt-clay size range. Mudrock is a general term that can be used to distinguish the finer-grained sedimentary rocks from sandstones or limestones.


Sources Consulted:
Farndon, J. (1998). Concise Encyclopedia Earth, Dorling Kindersley, Great Britain, 192.
Lapidus, D.F. (1987) Collins Dictionary of Geology, Winstanley, I. (Ed.), HarperCollins, Great Britain, 565pp.

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