User:Thparkth/Geology
From Wikipedia, the free encyclopedia
Geology is the science of the Earth’s physical structure and composition, its history, and of the processes that shape it. A wide spectrum of specialist fields exists within the discipline, including the study of physical landforms (Structural_geology), the search for economically worthwhile locations for mines and quarries (Economic_geology), the identification of oil and other fossil fuels (Petroleum_geology), and the study and attempted prediction of earthquakes and volcanoes (Seismology and Volcanology). Geology is also closely interrelated to other sciences such as Physics, Climatology, Paleontology and evolutionary biology.
The word Geology Geo .. logos.. etc. The word is also sometimes used about similar studies of other bodies of the solar system. However, specialised terms such as selenology (studies of the Moon), areology (of Mars), etc., are also in use.
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[edit] The Earth
Conceptually, the Earth is a blob of molten iron, nickel, silicon and magnesium compounds. The Earth being large enough to have a significant gravitational force, the lighter of these substances– in particular the silicates – have naturally risen to the top, and the heavier (the iron and nickel) sunk to the bottom; that is, to the center of the planet. Here the iron and nickel are subjected to such pressure that they are solid despite the immense heat. The light, silicon-rich compounds at the surface are exposed to the cosmos and have radiated their heat away to form a thin, crust-like layer of solid rock floating unstably on the liquid below.
The planet’s crust, which we are all so familiar with and take so much for granted, is only a small part of the story of the structure of the Earth. If the Earth were the size of a soccer ball, the average thickness of the crust would be less than a half-millimeter. On this precarious film of frozen rock, all of known life and all of human civilisation has developed.
The crust seems stable and eternal to us; but in fact it is an extremely dynamic place, with an ever-changing shape and structure. The two main processes responsible for this change are, firstly, convection currents inside the molten liquid mantle, which move "plates" of crust in various directions, along, against, above and beneath each other. This process is called plate tectonics and is responsible for earthquakes and volcanoes, but also for mountains and valleys. The second process is erosion, the continual wearing away of rocks by wind, rain, sea and ice.
[edit] Geological Timescales
The Earth is profoundly old. Current estimates age the planet at around 4.5 billion years. It is established that the same forces which operate today have been shaping the planet throughout that time.
