Geological history of Earth

Source: Wikipedia, the free encyclopedia.
Geologic time shown in a diagram called a geological clock, showing the relative lengths of the eons of Earth's history and noting major events

The geological history of the Earth follows the major geological events in Earth's past based on the

solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System
.

Initially, Earth was molten due to extreme volcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon afterwards, possibly as a result of the impact of a planetoid with the Earth. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered from comets, produced the oceans. However, in 2020, researchers reported that sufficient water to fill the oceans may have always been on the Earth since the beginning of the planet's formation.[1][2][3]

As the surface continually reshaped itself over hundreds of millions of years, continents formed and broke apart. They migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago, the earliest-known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia, 600 to 540 million years ago, then finally Pangaea, which broke apart 200 million years ago.

The present pattern of ice ages began about 40 million years ago, then intensified at the end of the Pliocene. The polar regions have since undergone repeated cycles of glaciation and thawing, repeating every 40,000–100,000 years. The Last Glacial Period of the current ice age ended about 10,000 years ago.

Plate tectonics from the Neoproterozoic to present[4]

Precambrian

The Precambrian includes approximately 90% of geologic time. It extends from 4.6 billion years ago to the beginning of the Cambrian Period (about 539

eons of Earth's prehistory (the Hadean, Archean and Proterozoic) and precedes the Phanerozoic eon.[5]

Major volcanic events altering the Earth's environment and causing extinctions may have occurred 10 times in the past 3 billion years.[6]

Hadean Eon

protoplanetary disc

During Hadean time (4.6–4

accretion disc from which Earth formed 4,500 million years ago.[7]
The Hadean Eon is not formally recognized, but it essentially marks the era before we have adequate record of significant solid rocks. The oldest dated zircons date from about 4,400 million years ago.[8][9][10]

Artist's impression of a Hadean landscape and the Moon looming large in the sky, both bodies still under extreme volcanism.

produced the oceans.[14] However, in 2020, researchers reported that sufficient water to fill the oceans may have always been on the Earth since the beginning of the planet's formation.[1][2][3]

During the Hadean the Late Heavy Bombardment occurred (approximately 4,100 to 3,800 million years ago) during which a large number of impact craters are believed to have formed on the Moon, and by inference on Earth, Mercury, Venus and Mars as well. However, some scientists argue against this hypothetical Late Heavy Bombardment, pointing out that the conclusion has been drawn from data which are not fully representative (only a few crater hotspots on the Moon have been analyzed).[15][16]

Archean Eon

tidal effects.[17]

The Earth of the early Archean (4,031 to 2,500 million years ago) may have had a different tectonic style. During this time, the Earth's

tectonic events. Some geologists view the sudden increase in aluminum content in zircons as an indicator of the beginning of plate tectonics.[18]

In contrast to the

graywackes, mudstones, volcanic sediments and banded iron formations. Greenstone belts are typical Archean formations, consisting of alternating high- and low-grade metamorphic rocks. The high-grade rocks were derived from volcanic island arcs, while the low-grade metamorphic rocks represent deep-sea sediments eroded from the neighboring island rocks and deposited in a forearc basin. In short, greenstone belts represent sutured protocontinents.[19]

The Earth's magnetic field was established 3.5 billion years ago. The solar wind flux was about 100 times the value of the modern Sun, so the presence of the magnetic field helped prevent the planet's atmosphere from being stripped away, which is what probably happened to the atmosphere of Mars. However, the field strength was lower than at present and the magnetosphere was about half the modern radius.[20]

Proterozoic Eon

The geologic record of the Proterozoic (2,500 to 538.8 million years ago

epicontinental seas; furthermore, many of these rocks are less metamorphosed than Archean-age ones, and plenty are unaltered.[22] Study of these rocks shows that the eon featured massive, rapid continental accretion (unique to the Proterozoic), supercontinent cycles, and wholly modern orogenic activity.[23] Roughly 750 million years ago,[24] the earliest-known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia, 600–540 Ma.[9][25]

The first-known glaciations occurred during the Proterozoic, one that began shortly after the beginning of the eon, while there were at least four during the Neoproterozoic, climaxing with the Snowball Earth of the Varangian glaciation.[26]

Artist's rendition of a fully-frozen Snowball Earth with no remaining liquid surface water.

Phanerozoic

The Phanerozoic Eon is the current eon in the geologic timescale. It covers roughly 539 million years. During this period continents drifted apart, but eventually collected into a single landmass known as

Pangea
, before splitting again into the current continental landmasses.

The Phanerozoic is divided into three eras – the Paleozoic, the Mesozoic and the Cenozoic.

Most of the evolution of multicellular life occurred during this time period.

Paleozoic Era

The Paleozoic era spanned roughly 539 to 251 million years ago (Ma)

geologic periods: from oldest to youngest, they are the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Geologically, the Paleozoic starts shortly after the breakup of a supercontinent called Pannotia and at the end of a global ice age. Throughout the early Paleozoic, Earth's landmass was broken up into a substantial number of relatively small continents. Toward the end of the era, the continents gathered together into a supercontinent called Pangaea
, which included most of Earth's land area.

Cambrian Period

The Cambrian is a major division of the

geologic timescale that begins about 538.8 ± 0.2 Ma.[28] Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Pannotia. The waters of the Cambrian period appear to have been widespread and shallow. Continental drift rates may have been anomalously high. Laurentia, Baltica and Siberia remained independent continents following the break-up of the supercontinent of Pannotia. Gondwana started to drift toward the South Pole. Panthalassa covered most of the southern hemisphere, and minor oceans included the Proto-Tethys Ocean, Iapetus Ocean and Khanty Ocean
.

Ordovician period

The Ordovician period started at a major extinction event called the Cambrian–Ordovician extinction event some time about 485.4 ± 1.9 Ma.[9] During the Ordovician the southern continents were collected into a single continent called Gondwana. Gondwana started the period in the equatorial latitudes and, as the period progressed, drifted toward the South Pole. Early in the Ordovician the continents Laurentia, Siberia and Baltica were still independent continents (since the break-up of the supercontinent Pannotia earlier), but Baltica began to move toward Laurentia later in the period, causing the Iapetus Ocean to shrink between them. Also, Avalonia broke free from Gondwana and began to head north toward Laurentia. The Rheic Ocean was formed as a result of this. By the end of the period, Gondwana had neared or approached the pole and was largely glaciated.

The Ordovician came to a close in a series of extinction events that, taken together, comprise the second-largest of the five major extinction events in Earth's history in terms of percentage of genera that became extinct. The only larger one was the Permian-Triassic extinction event. The extinctions occurred approximately 447 to 444 million years ago [9] and mark the boundary between the Ordovician and the following Silurian Period.

The most-commonly accepted theory is that these events were triggered by the onset of an ice age, in the Hirnantian faunal stage that ended the long, stable greenhouse conditions typical of the Ordovician. The ice age was probably not as long-lasting as once thought; study of oxygen isotopes in fossil brachiopods shows that it was probably no longer than 0.5 to 1.5 million years.[29] The event was preceded by a fall in atmospheric carbon dioxide (from 7000ppm to 4400ppm) which selectively affected the shallow seas where most organisms lived. As the southern supercontinent Gondwana drifted over the South Pole, ice caps formed on it. Evidence of these ice caps has been detected in Upper Ordovician rock strata of North Africa and then-adjacent northeastern South America, which were south-polar locations at the time.

Silurian Period

The Silurian is a major division of the

Euramerica. The vast ocean of Panthalassa covered most of the northern hemisphere. Other minor oceans include Proto-Tethys, Paleo-Tethys, Rheic Ocean, a seaway of Iapetus Ocean (now in between Avalonia and Laurentia), and newly formed Ural Ocean
.

Devonian Period

The Devonian spanned roughly from 419 to 359 Ma.

Caledonian Mountains in Great Britain and Scandinavia. The southern continents remained tied together in the supercontinent of Gondwana
. The remainder of modern Eurasia lay in the Northern Hemisphere. Sea levels were high worldwide, and much of the land lay submerged under shallow seas. The deep, enormous Panthalassa (the "universal ocean") covered the rest of the planet. Other minor oceans were Paleo-Tethys, Proto-Tethys, Rheic Ocean and Ural Ocean (which was closed during the collision with Siberia and Baltica).

Carboniferous Period

The Carboniferous extends from about 358.9 ± 0.4 to about 298.9 ± 0.15 Ma.[9]

A global drop in sea level at the end of the Devonian reversed early in the

Pennsylvanian period.[30]

The Carboniferous was a time of active mountain building, as the supercontinent Pangea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America-Europe (

Ural mountains. There were two major oceans in the Carboniferous: the Panthalassa and Paleo-Tethys. Other minor oceans were shrinking and eventually closed the Rheic Ocean (closed by the assembly of South and North America), the small, shallow Ural Ocean (which was closed by the collision of Baltica, and Siberia
continents, creating the Ural Mountains) and Proto-Tethys Ocean.

Pangaea separation animation

Permian Period

The Permian extends from about 298.9 ± 0.15 to 252.17 ± 0.06 Ma.[9]

During the Permian all the Earth's major land masses, except portions of East Asia, were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean (Panthalassa, the universal sea), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmasses create climates with extreme variations of heat and cold ("continental climate") and monsoon conditions with highly seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea.

Mesozoic Era

Plate tectonics - 249 million years ago
Plate tectonics - 290 million years ago

The Mesozoic extended roughly from 252 to 66 million years ago.[9]

After the vigorous convergent plate mountain-building of the late

Atlantic
coastline (such as along the U.S. East Coast) today.

Triassic Period

The Triassic Period extends from about 252.17 ± 0.06 to 201.3 ± 0.2 Ma.[9] During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent centered more or less on the equator, called Pangaea ("all the land"). This took the form of a giant "Pac-Man" with an east-facing "mouth" constituting the Tethys sea, a vast gulf that opened farther westward in the mid-Triassic, at the expense of the shrinking Paleo-Tethys Ocean, an ocean that existed during the Paleozoic.

The remainder was the world-ocean known as Panthalassa ("all the sea"). All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates; thus, very little is known of the Triassic open ocean. The supercontinent Pangaea was rifting during the Triassic—especially late in the period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangea—which separated New Jersey from Morocco—are of Late Triassic age; in the U.S., these thick sediments comprise the Newark Supergroup.[32] Because of the limited shoreline of one super-continental mass, Triassic marine deposits are globally relatively rare; despite their prominence in Western Europe, where the Triassic was first studied. In North America, for example, marine deposits are limited to a few exposures in the west. Thus Triassic stratigraphy is mostly based on organisms living in lagoons and hypersaline environments, such as Estheria crustaceans and terrestrial vertebrates.[33]

Jurassic Period

The Jurassic Period extends from about 201.3 ± 0.2 to 145.0 Ma.[9] During the early

Yucatan Peninsula. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous Period, when Gondwana itself rifted apart.[34]
The In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface.
Cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny.[37] Important Jurassic exposures are also found in Russia, India, South America, Japan, Australasia
and the United Kingdom.

Cretaceous Period

Plate tectonics - 100 Ma,[9] Cretaceous period

The Cretaceous Period extends from circa 145 million years ago to 66 million years ago.[9]

During the

North American Cordillera, as the Nevadan orogeny was followed by the Sevier and Laramide orogenies. Though Gondwana was still intact in the beginning of the Cretaceous, Gondwana itself broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); thus, the South Atlantic and Indian Oceans were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels
worldwide.

To the north of Africa the

formations from North America include the rich marine fossils of Kansas's Smoky Hill Chalk Member and the terrestrial fauna of the late Cretaceous Hell Creek Formation. Other important Cretaceous exposures occur in Europe and China. In the area that is now India, massive lava beds called the Deccan Traps
were laid down in the very late Cretaceous and early Paleocene.

Cenozoic Era

The Cenozoic Era covers the 66 million years since the Cretaceous–Paleogene extinction event up to and including the present day. By the end of the Mesozoic era, the continents had rifted into nearly their present form. Laurasia became North America and Eurasia, while Gondwana split into South America, Africa, Australia, Antarctica and the Indian subcontinent, which collided with the Asian plate. This impact gave rise to the Himalayas. The Tethys Sea, which had separated the northern continents from Africa and India, began to close up, forming the Mediterranean Sea.

Paleogene Period

The Paleogene (alternatively Palaeogene)

geologic time that began 66 and ended 23.03 Ma[9] and comprises the first part of the Cenozoic Era. This period consists of the Paleocene, Eocene and Oligocene
Epochs.

Paleocene Epoch

The Paleocene, lasted from 66 million years ago to 56 million years ago.[9]

In many ways, the Paleocene continued processes that had begun during the late Cretaceous Period. During the Paleocene, the continents continued to drift toward their present positions. Supercontinent Laurasia had not yet separated into three continents. Europe and Greenland were still connected. North America and Asia were still intermittently joined by a land bridge, while Greenland and North America were beginning to separate.[41] The Laramide orogeny of the late Cretaceous continued to uplift the Rocky Mountains in the American west, which ended in the succeeding epoch. South and North America remained separated by equatorial seas (they joined during the Neogene); the components of the former southern supercontinent Gondwana continued to split apart, with Africa, South America, Antarctica and Australia pulling away from each other. Africa was heading north toward Europe, slowly closing the Tethys Ocean, and India began its migration to Asia that would lead to a tectonic collision and the formation of the Himalayas.

Eocene Epoch

During the

Ma, the warm equatorial currents were deflected away from Antarctica, and an isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the ocean surrounding Antarctica began to freeze, sending cold water and ice floes north, reinforcing the cooling. The present pattern of ice ages began about 40 million years ago.[citation needed
]

The northern

Himalayan
orogeny.

Oligocene Epoch

The Oligocene Epoch extends from about 34 million years ago to 23 million years ago.[9] During the Oligocene the continents continued to drift toward their present positions.

faunas of the two regions are very similar. During the Oligocene, South America was finally detached from Antarctica and drifted north toward North America. It also allowed the Antarctic Circumpolar Current
to flow, rapidly cooling the continent.

Neogene Period

The Neogene Period is a unit of

geologic time starting 23.03 Ma.[9] and ends at 2.588 Ma. The Neogene Period follows the Paleogene Period. The Neogene consists of the Miocene and Pliocene and is followed by the Quaternary
Period.

Miocene Epoch

The Miocene extends from about 23.03 to 5.333 Ma.[9]

During the

Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea resulting in the Messinian salinity crisis
near the end of the Miocene.

Pliocene Epoch

The Pliocene extends from 5.333 million years ago to 2.588 million years ago.[9] During the Pliocene continents continued to drift toward their present positions, moving from positions possibly as far as 250 kilometres (155 mi) from their present locations to positions only 70 km from their current locations.

South America became linked to North America through the

marsupial faunas. The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean. Africa's collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean. Sea level changes exposed the land-bridge between Alaska and Asia. Near the end of the Pliocene, about 2.58 million years ago (the start of the Quaternary Period), the current ice age
began. The polar regions have since undergone repeated cycles of glaciation and thaw, repeating every 40,000–100,000 years.

Quaternary Period

Pleistocene Epoch

The Pleistocene extends from 2.588 million years ago to 11,700 years before present.

plates
upon which they sit probably having moved no more than 100 kilometres (62 mi) relative to each other since the beginning of the period.

Holocene Epoch
Current Earth - without water, elevation greatly exaggerated (click/enlarge to "spin" 3D-globe).

The Holocene Epoch began approximately 11,700 calendar years before present[9] and continues to the present. During the Holocene, continental motions have been less than a kilometer.

The

current ice age ended about 10,000 years ago.[42] Ice melt caused world sea levels to rise about 35 metres (115 ft) in the early part of the Holocene. In addition, many areas above about 40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 metres (591 ft) over the late Pleistocene and Holocene, and are still rising today. The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea. Holocene marine fossils are known from Vermont, Quebec, Ontario and Michigan. Other than higher latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed, floodplain and cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely upthrusting of non-glacial origin. Post-glacial rebound in Scandinavia resulted in the emergence of coastal areas around the Baltic Sea, including much of Finland. The region continues to rise, still causing weak earthquakes across Northern Europe. The equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea
phase, to near its present boundaries.

See also

References

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  17. ^ "Earth-Moon Dynamics". Lunar and Planetary Institute. Retrieved September 2, 2022.
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  19. ^ Stanley 1999, pp. 302–303
  20. ^ Staff (March 4, 2010). "Oldest measurement of Earth's magnetic field reveals battle between Sun and Earth for our atmosphere". Physorg.news. Retrieved 2010-03-27.
  21. ^ "Stratigraphic Chart 2022" (PDF). International Stratigraphic Commission. February 2022. Retrieved 25 April 2022.
  22. ^ Stanley 1999, p. 315
  23. ^ Stanley 1999, pp. 315–318, 329–332
  24. ^ International Stratigraphic Chart 2008, International Commission on Stratigraphy
  25. doi:10.1511/2004.4.324. Archived from the original
    on 2007-07-13. Retrieved 2007-03-05.
  26. ^ Stanley 1999, pp. 320–321, 325
  27. ^ "Stratigraphic Chart 2022" (PDF). International Stratigraphic Commission. February 2022. Retrieved 25 April 2022.
  28. ^ "Stratigraphic Chart 2022" (PDF). International Stratigraphic Commission. February 2022. Retrieved 25 April 2022.
  29. ^ Stanley 1999, p. 358
  30. ^ Stanley 1999, p. 414
  31. ^ Stanley 1999, pp. 414–416
  32. ^ Olsen, Paul E. (1997). "Great Triassic Assemblages Pt 1 - The Chinle and Newark". Dinosaurs and the History of Life. Lamont–Doherty Earth Observatory of Columbia University.
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  34. ^ "Pangea Begins to Rift Apart". C. R. Scotese. Retrieved 2007-07-19.
  35. ^ "Land and sea during Jurassic". Urwelt museum hauff. Archived from the original on 2007-07-14. Retrieved 2007-07-19.
  36. ^ "Jurassic Rocks – 208 to 146 million years ago". nationalatlas.gov. United States Department of the Interior. Archived from the original on 2014-09-30. Retrieved 2007-07-19.
  37. .
  38. ^ Dougal Dixon et al., Atlas of Life on Earth, (New York: Barnes & Noble Books, 2001), p. 215.
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  40. ^ Stanley 1999, pp. 279–281
  41. ^ Staff. "Paleoclimatology - The Study of Ancient Climates". Page Paleontology Science Center. Archived from the original on 2011-08-25. Retrieved 2007-03-02.

Further reading

  • Stanley, Steven M. (1999). Earth system history (New ed.). New York: W. H. Freeman. .

External links