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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.
The geologic time scale is a way of representing deep time based on events that have occurred throughout Earth's history, a time span of about 4.54 ± 0.05 Ga (4.54 billion years). [3]
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.
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.
Chalcolithic (or "Eneolithic", "Copper Age") Ancient history (The Bronze and Iron Ages are not part of prehistory for all regions and civilizations who had adopted or developed a writing system.) Bronze Age; Iron Age; Late Middle Ages. Renaissance; Early modern history; Modern history. Industrial Age (1760–1970) Machine Age (1880–1945) Age ...
The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia. [32] [33 ...
The extinction event wiped out three-quarters of all life on Earth more than 200 million years ago ... Scientists thought a warming Earth led to the age of the dinosaurs. That might be wrong.
c. 4,566 ±2 Ma – A protoplanetary disc (from which Earth eventually forms) emerges around the young Sun, which is in its T Tauri stage. c. 4,560–4,550 Ma – Proto-Earth forms at the outer (cooler) edge of the habitable zone of the Solar System.