Physical Processes
Rock Cycle
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The rock cycle is the continual transformation of rock among three families over geologic time: sedimentary rock formed as weathered and eroded fragments are compacted and cemented in layers, igneous rock formed as magma cools and solidifies, and metamorphic rock formed when existing rock is transformed by heat and pressure without fully melting. Each type can, over millions of years, be converted into either of the others.
Facts
TimescaleAmong the slowest processes on this atlas's spine: a full cycle from one rock type through another operates over millions of years. 1 Spans more than one of the atlas's process-type categories (sedimentary formation is geomorphological, igneous formation is tectonic); recorded here as geomorphological for its dominant surface expression, with this note carrying the tectonic half honestly rather than silently. First Proposed YearJames Hutton's Theory of the Earth, read to the Royal Society of Edinburgh on 7 March and 4 April 1785 and published in full in 1788, described a repeating cycle of seabed deposition, uplift and erosion that later became known as the rock cycle. Hutton's own text does not use the phrase 'rock cycle' itself; the primary source describes the process rather than naming it. Disputed
Process TypeThe rock cycle genuinely spans both the geomorphological (sedimentary) and tectonic (igneous) halves of this atlas's process-type vocabulary; geomorphological is recorded as the primary value because the cycle's defining, name-giving motion is surface-level recycling, not because the tectonic half is any less real. Cross-Tradition Connections
Demonstrated By
The canyon walls expose a visible sequence of sedimentary rock layers, a textbook illustration of the rock cycle's sedimentary half.
In the Other Atlases
- Also in Science Atlas: Rock Cycle, the same subject.
Sources
1. British Geological Survey
British Geological SurveyGeological processes, Discovering GeologyQuote, Geological processes, Discovering Geology
These process are shown in the rock cycle, which describes the ways in which rocks are slowly recycled over millions of years and transformed between the three rock types: sedimentary, igneous and metamorphic rocks.
1. British Geological Survey
2. James Hutton (Wikipedia)
Wikimedia FoundationTheory of rock formations sectionQuote, Theory of rock formations section
Hutton reasoned that there must have been innumerable cycles, each involving deposition on the seabed, uplift with tilting and erosion then undersea again for further layers to be deposited.
Andes (Wikipedia)
Wikimedia FoundationDemonstrated By: The Andes, Geology, Orogeny subsectionQuote, Demonstrated By: The Andes, Geology, Orogeny subsection
It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting, faulting, and folding of sedimentary and metamorphic rocks of the ancient cratons to the east.
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