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The geologic time scale, proportionally represented as a log-spiral with some major events in Earth's history. A megaannus (Ma) represents one million (10 6) years.. The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth.
In 1862, the physicist William Thomson, 1st Baron Kelvin published calculations that fixed the age of Earth at between 20 million and 400 million years. [19] [20] He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface temperature gradient to decrease to its present value.
Even though the Sun won't destroy Earth until December 31, all animals will die out by the end of May. Use of the geologic calendar as a conceptual aid dates back at least to the mid 20th century, for example in Richard Carrington's 1956 book A Guide to Earth History [ 3 ] and Gove Hambidge's 1941 chapter in the book Climate and Man . [ 4 ]
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth itself.
"Chart of The Global Boundary Stratotype Sections and Points (GSSP): chart". stratigraphy.science.purdue.edu. Archived from the original on 2022-06-30. "GSSP Table - All Periods". timescalefoundation.org. Archived from the original on 2023-11-30. "GSSPs and Continental drift 3D views". ghkclass.net. Archived from the original on 2023-12-08.
The Earth of the early Archean may have had a different tectonic style. It is widely believed that the early Earth was dominated by vertical tectonic processes, such as stagnant lid , [ 19 ] [ 20 ] heat-pipe , [ 21 ] or sagduction , [ 22 ] [ 23 ] [ 24 ] which eventually transitioned to plate tectonics during the planet's mid-stage evolution.
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Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geological region, and eventually, the entire geologic record of the Earth .