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Was there ever a collision of the Earth with another planet Theia, giving birth to the Moon? [1] There is compelling evidence, such as measures of a shorter duration of the Earth's rotation and lunar month in the past, pointing to a Moon much closer to Earth during the early stages of the Solar System.
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Magmatic underplating has been identified using multiple techniques that are non-specific to the area in which they are used. Geochemistry allows geologists to determine levels of association between igneous units: in the Karoo Province of southern Africa, large volumes of rhyolite along the continental margin were produced from melts with initially basaltic compositions.
The following outline is provided as an overview of and topical guide to geology: . Geology – one of the Earth sciences – is the study of the Earth, with the general exclusion of present-day life, flow within the ocean, and the atmosphere.
QAPF diagram for the classification of plutonic rocks Devils Tower, United States, an igneous intrusion exposed when the surrounding softer rock eroded away. Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
Hutton's Unconformity at Jedburgh, Scotland, illustrated by John Clerk in 1787 and photographed in 2003.. An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous.
Columnar jointing in Giant's Causeway in Northern Ireland Columnar jointing in the Alcantara Gorge, Sicily. Columnar jointing is a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms (basalt prisms), or columns.