Thegeological history of Earth follows the major geological events in Earth's past based on thegeologic time scale, a system ofchronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formedapproximately 4.54 billion years ago through accretion from thesolar nebula, a disk-shaped mass of dust and gas remaining from the formation of the Sun, which also formed the rest of theSolar System.
Initially, Earth was molten due to extremevolcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solidcrust when water began accumulating in the atmosphere. TheMoon formed soon afterwards, possibly as a result of the impact of a planetoid with Earth.Outgassing and volcanic activity produced the primordial atmosphere.Condensingwater vapor, augmented by ice delivered fromasteroids,produced the oceans. However, in 2020, researchers reported thatsufficient water to fill the oceans may have always been onEarth 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. Theymigrated across the surface, occasionally combining to form asupercontinent. Roughly750 million years ago, the earliest-known supercontinentRodinia, began to break apart. The continents later recombined to formPannotia,600 to 540 million years ago, then finallyPangaea, which broke apart200 million years ago.
The present pattern ofice ages began about40 million years ago, then intensified at the end of thePliocene. The polar regions have since undergone repeated cycles of glaciation and thawing, repeating every 40,000–100,000 years. TheLast Glacial Period of thecurrent ice age ended about 10,000 years ago.
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 million years ago). It includes the first three of the foureons of Earth's prehistory (theHadean,Archean, andProterozoic) and precedes thePhanerozoic eon.[6]
Major volcanic events altering Earth's environment and causingextinctions may have occurred 10 times in the past 3 billion years.[7]
During Hadean time (4.6–4Ga), theSolar System was forming, probably within a large cloud of gas and dust around the Sun, called anaccretion disc from whichEarth formed4,500 million years ago.[8]The Hadean Eon is not formally recognized, but it essentially marks the era before we have adequate record of significant solid rocks. The oldest datedzircons date from about4,400 million years ago.[9][10][11]
Earth was initially molten due to extremevolcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solidcrust when water began accumulating in the atmosphere. TheMoon formed soon afterwards, possibly as a result of theimpact of a large planetoid with Earth.[12][13] More recent potassium isotopic studies suggest that the Moon was formed by a smaller, high-energy, high-angular-momentum giant impact cleaving off a significant portion of Earth.[14] Some of this object's mass merged with Earth, significantly altering its internal composition, and a portion was ejected into space. Some of the material survived to form the orbiting Moon. Outgassing andvolcanic activity produced the primordial atmosphere. Condensingwater vapor, augmented by ice delivered fromcomets,produced the oceans.[15] However, in 2020, researchers reported thatsufficient water to fill the oceans may have always been onEarth since the beginning of theplanet's formation.[1][2][3]
During the Hadean theLate Heavy Bombardment occurred (approximately4,100 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, andMars 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).[16][17]
Earth of the early Archean (4,031 to 2,500 million years ago) may have had a different tectonic style. It is widely believed that the early Earth was dominated by vertical tectonic processes, such asstagnant lid,[19][20]heat-pipe,[21] orsagduction,[22][23][24] which eventually transitioned to plate tectonics during the planet's mid-stage evolution. However, an alternative view proposes that Earth never experienced a vertical tectonic phase and that plate tectonics have been active throughout its entire history.[25][26][27] During this time, Earth'scrust cooled enough that rocks and continental plates began to form. Some scientists think because Earth was hotter in the past,[28][29] plate tectonic activity was more vigorous than it is today, resulting in a much greater rate of recycling of crustal material. This may have preventedcratonization and continent formation until themantle cooled and convection slowed down. Others argue that the subcontinental lithospheric mantle is too buoyant tosubduct and that the lack of Archean rocks is a function oferosion and subsequenttectonic events. Some geologists view the sudden increase in aluminum content in zircons as an indicator of the beginning ofplate tectonics.[30]
UnlikeProterozoic rocks, Archean rocks are distinguished by the presence of heavily metamorphosed deep-water sediments, such asgraywackes,mudstones, volcanic sediments andbanded iron formations.Greenstone belts are typical Archean formations, consisting of alternating high- and low-grade metamorphic rocks. The high-grade rocks were derived from volcanicisland arcs, while the low-grade metamorphic rocks represent deep-sea sediments eroded from the neighboring island rocks and deposited in aforearc basin. In short, greenstone belts represent sutured protocontinents.[31]
TheEarth's magnetic field was established 3.5 billion years ago. Thesolar wind flux was about 100 times the value of the modernSun, so the presence of the magnetic field helped prevent the planet's atmosphere from being stripped away, which is what probably happened to theatmosphere of Mars. However, the field strength was lower than at present and themagnetosphere was about half the modern radius.[32]
The geologic record of the Proterozoic (2,500 to 538.8 million years ago[33]) is more complete than that for the precedingArchean. In contrast to the deep-water deposits of the Archean, the Proterozoic features manystrata that were laid down in extensive shallowepicontinental seas; furthermore, many of these rocks are lessmetamorphosed than Archean-age ones, and plenty are unaltered.[34] Study of these rocks shows that the eon featured massive, rapidcontinental accretion (unique to the Proterozoic),supercontinent cycles, and wholly modernorogenic activity.[35] Roughly750 million years ago,[36] the earliest-known supercontinentRodinia, began to break apart. The continents later recombined to formPannotia, 600–540 Ma.[10][37]
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 theSnowball Earth of the Varangian glaciation.[38]
ThePhanerozoic 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 asPangea, before splitting again into the current continental landmasses.[citation needed]
The Phanerozoic is divided into three eras – thePaleozoic, theMesozoic and theCenozoic.
Most of the evolution of multicellular life occurred during this time period.
ThePaleozoic era spanned roughly539 to 251 million years ago,[39] and is subdivided into sixgeologic periods: from oldest to youngest, they are theCambrian,Ordovician,Silurian,Devonian,Carboniferous andPermian. Geologically, thePaleozoic starts shortly after the breakup of a supercontinent calledPannotia 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 calledPangaea, which included most of Earth's land area.
TheCambrian is a major division of thegeologic timescale that begins about 538.8 ± 0.2 million years ago.[40]Cambrian continents are thought to have resulted from the breakup of aNeoproterozoic 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 andSiberia 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 theProto-Tethys Ocean,Iapetus Ocean andKhanty Ocean.
TheOrdovician period started at a major extinction event called theCambrian–Ordovician extinction event some time about 485.4 ± 1.9 million years ago.[10] During theOrdovician 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), butBaltica 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. TheRheic 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.[citation needed]
The Ordovician came to a close in a series ofextinction events that, taken together, comprise the second-largest of the five major extinction events inEarth's history in terms of percentage ofgenera that became extinct. The only larger one was the Permian-Triassic extinction event. The extinctions occurred approximately447 to 444 million years ago[10] and mark the boundary between the Ordovician and the followingSilurian Period.
The most-commonly accepted theory is that these events were triggered by the onset of anice age, in the Hirnantian faunal stage that ended the long, stablegreenhouse conditions typical of the Ordovician. The ice age was probably not as long-lasting as once thought; study of oxygenisotopes in fossil brachiopods shows that it was probably no longer than 0.5 to 1.5 million years.[41] 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 supercontinentGondwana 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.[citation needed]
TheSilurian is a major division of thegeologic timescale that started about 443.8 ± 1.5 million years ago.[10] During theSilurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian ice caps were less extensive than those of the late Ordovician glaciation. The melting of ice caps and glaciers contributed to a rise insea levels, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming anunconformity. Othercratons and continent fragments drifted together near the equator, starting the formation of a second supercontinent known asEuramerica. 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 formedUral Ocean.
TheDevonian spanned roughly from 419 to 359 million years ago.[10] The period was a time of great tectonic activity, asLaurasia and Gondwana drew closer together. The continent Euramerica (or Laurussia) was created in the early Devonian by the collision of Laurentia and Baltica, which rotated into the natural dry zone along theTropic of Capricorn. In these near-deserts, theOld Red Sandstone sedimentary beds formed, made red by the oxidized iron (hematite) characteristic of drought conditions. Near the equator Pangaea began to consolidate from the plates containing North America and Europe, further raising the northernAppalachian Mountains and forming theCaledonian Mountains inGreat Britain andScandinavia. The southern continents remained tied together in the supercontinent ofGondwana. 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).
TheCarboniferous extends from about 358.9 ± 0.4 to about 298.9 ± 0.15 million years ago.[10]
A global drop in sea level at the end of the Devonian reversed early in theCarboniferous; this created the widespread epicontinental seas and carbonate deposition of theMississippian. There was also a drop in south polar temperatures; southern Gondwana was glaciated throughout the period, though it is uncertain if the ice sheets were a holdover from the Devonian or not. These conditions apparently had little effect in the deep tropics, where lushcoal swamps flourished within 30 degrees of the northernmost glaciers. A mid-Carboniferous drop in sea-level precipitated a major marine extinction, one that hitcrinoids andammonites especially hard. This sea-level drop and the associated unconformity in North America separate theMississippian period from thePennsylvanian period.[42]
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 (Laurussia) along the present line of easternNorth America. This continental collision resulted in theHercynian orogeny in Europe, and theAlleghenian orogeny in North America; it also extended the newly uplifted Appalachians southwestward as theOuachita Mountains.[43] In the same time frame, much of present easternEurasian Plate welded itself to Europe along the line of theUral Mountains. There were two major oceans in the Carboniferous: the Panthalassa and Paleo-Tethys. Other minor oceans were shrinking and eventually closed theRheic Ocean (closed by the assembly of South and North America), the small, shallowUral Ocean (which was closed by the collision ofBaltica, andSiberia continents, creating the Ural Mountains) and Proto-Tethys Ocean.
ThePermian extends from about 298.9 ± 0.15 to 252.17 ± 0.06 million years ago.[10]
During thePermian all Earth's major landmasses, except portions of East Asia, were collected into a single supercontinent known asPangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean (Panthalassa, theuniversal sea), and thePaleo-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.
TheMesozoic extended roughly from252 to 66 million years ago.[10]
After the vigorous convergent plate mountain-building of the latePaleozoic,Mesozoic tectonic deformation was comparatively mild. Nevertheless, the era featured the dramatic rifting of the supercontinentPangaea. Pangaea gradually split into a northern continent,Laurasia, and a southern continent,Gondwana. This created thepassive continental margin that characterizes most of theAtlantic coastline (such as along the U.S. East Coast) today.
TheTriassic Period extends from about 252.17 ± 0.06 to 201.3 ± 0.2 million years ago.[10] During theTriassic, almost all Earth's landmass was concentrated into a singlesupercontinent centered more or less on the equator, calledPangaea ("all the land"). This took the form of a giant "Pac-Man" with an east-facing "mouth" constituting theTethys sea, a vast gulf that opened farther westward in the mid-Triassic, at the expense of the shrinkingPaleo-Tethys Ocean, an ocean that existed during thePaleozoic.
The remainder was the world-ocean known asPanthalassa ("all the sea"). All the deep-ocean sediments laid down during the Triassic have disappeared throughsubduction 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 therift that marks the initial break-up of Pangea—which separatedNew Jersey fromMorocco—are of Late Triassic age; in the U.S., these thick sediments comprise theNewark Supergroup.[44]Because of the limited shoreline of one super-continental mass, Triassic marine deposits are globally relatively rare; despite their prominence inWestern Europe, where the Triassic was first studied. InNorth America, for example, marine deposits are limited to a few exposures in the west. Thus Triassicstratigraphy is mostly based on organisms living in lagoons and hypersaline environments, such asEstheria crustaceans and terrestrial vertebrates.[45]
TheJurassic Period extends from about 201.3 ± 0.2 to 145.0 million years ago.[10]During the earlyJurassic, the supercontinentPangaea broke up into the northern supercontinentLaurasia and the southern supercontinentGondwana; theGulf of Mexico opened in the new rift between North America and what is nowMexico'sYucatan Peninsula. The Jurassic NorthAtlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous Period, when Gondwana itself rifted apart.[46]TheTethys Sea closed, and theNeotethys basin appeared. Climates were warm, with no evidence ofglaciation. As in the Triassic, there was apparently no land near either pole, and no extensive ice caps existed. The Jurassic geological record is good in westernEurope, where extensive marine sequences indicate a time when much of the continent was submerged under shallow tropical seas; famous locales include theJurassic CoastWorld Heritage Site and the renowned late Jurassiclagerstätten ofHolzmaden andSolnhofen.[47]In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface.[48] Though theepicontinentalSundance Sea left marine deposits in parts of the northern plains of theUnited States andCanada during the late Jurassic, most exposed sediments from this period are continental, such as thealluvial deposits of theMorrison Formation. The first of several massivebatholiths were emplaced in the northernCordillera beginning in the mid-Jurassic, marking theNevadan orogeny.[49] Important Jurassic exposures are also found in Russia, India, South America, Japan,Australasia and the United Kingdom.
TheCretaceous Period extends from circa145 million years ago to66 million years ago.[10]
During theCretaceous, the latePaleozoic-early Mesozoicsupercontinent ofPangaea completed its breakup into present daycontinents, although their positions were substantially different at the time. As theAtlantic Ocean widened, the convergent-marginorogenies that had begun during the Jurassic continued in theNorth American Cordillera, as theNevadan orogeny was followed by theSevier andLaramide orogenies. Though Gondwana was still intact in the beginning of the Cretaceous,Gondwana itself broke up asSouth America,Antarctica andAustralia rifted away fromAfrica (thoughIndia andMadagascar remained attached to each other); thus, the South Atlantic andIndian Oceans were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raisingeustatic sea levels worldwide.
To the north of Africa theTethys Sea continued to narrow. Broad shallow seas advanced across centralNorth America (theWestern Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched betweencoal beds. At the peak of the Cretaceoustransgression, one-third of Earth's present land area was submerged.[50] The Cretaceous is justly famous for itschalk; indeed, more chalk formed in the Cretaceous than in any other period in thePhanerozoic.[51]Mid-ocean ridge activity—or rather, the circulation of seawater through the enlarged ridges—enriched the oceans in calcium; this made the oceans more saturated, as well as increased the bioavailability of the element forcalcareous nanoplankton.[52] These widespreadcarbonates and othersedimentary deposits make the Cretaceous rock record especially fine. Famousformations from North America include the rich marine fossils ofKansas'sSmoky Hill Chalk Member and the terrestrial fauna of the late CretaceousHell Creek Formation. Other important Cretaceous exposures occur inEurope andChina. In the area that is now India, massivelava beds called theDeccan Traps were laid down in the very late Cretaceous and early Paleocene.
TheCenozoic Era covers the 66 million years since theCretaceous–Paleogene extinction event up to and including the present day. By the end of theMesozoic era, the continents had rifted into nearly their present form.Laurasia becameNorth America andEurasia, whileGondwana split intoSouth America,Africa,Australia,Antarctica and theIndian 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 theMediterranean Sea.
ThePaleogene (alternativelyPalaeogene)Period is a unit ofgeologic time that began 66 and ended 23.03 Ma[10] and comprises the first part of theCenozoic Era. This period consists of thePaleocene,Eocene andOligocene Epochs.
ThePaleocene, lasted from66 million years ago to56 million years ago.[10]
In many ways, thePaleocene continued processes that had begun during the late Cretaceous Period. During the Paleocene, thecontinents continued to drift toward their present positions. SupercontinentLaurasia had not yet separated into three continents.Europe andGreenland were still connected.North America andAsia were still intermittently joined by a land bridge, while Greenland and North America were beginning to separate.[53] TheLaramide orogeny of the late Cretaceous continued to uplift theRocky Mountains in the American west, which ended in the succeeding epoch. South and North America remained separated by equatorial seas (they joined during theNeogene); the components of the former southern supercontinentGondwana continued to split apart, withAfrica, South America,Antarctica andAustralia pulling away from each other. Africa was heading north towardEurope, slowly closing theTethys Ocean, andIndia began its migration to Asia that would lead to a tectonic collision and the formation of theHimalayas.
During theEocene (56 million years ago -33.9 million years ago),[10] the continents continued to drift toward their present positions. At the beginning of the period, Australia and Antarctica remained connected, and warmequatorial currents mixed with colder Antarctic waters, distributing the heat around the world and keeping global temperatures high. But when Australia split from the southern continent around 45Ma, 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 ofice ages began about40 million years ago.[54]
The northernsupercontinent ofLaurasia began to break up, asEurope,Greenland andNorth America drifted apart. In western North America,mountain building started in the Eocene, and huge lakes formed in the high flat basins among uplifts. In Europe, theTethys Sea finally vanished, while the uplift of theAlps isolated its final remnant, theMediterranean, and created another shallow sea with islandarchipelagos to the north. Though the NorthAtlantic was opening, a land connection appears to have remained between North America and Europe since the faunas of the two regions are very similar.India continued its journey away fromAfrica and began its collision withAsia, creating theHimalayan orogeny.
TheOligocene Epoch extends from about34 million years ago to23 million years ago.[10] During theOligocene the continents continued to drift toward their present positions.
Antarctica continued to become more isolated and finally developed a permanentice cap.Mountain building in westernNorth America continued, and theAlps started to rise inEurope as theAfrican Plate continued to push north into theEurasian Plate, isolating the remnants ofTethys Sea. A brief marine incursion marks the early Oligocene in Europe. There appears to have been a land bridge in the early Oligocene betweenNorth America andEurope since thefaunas of the two regions are very similar. During the Oligocene,South America was finally detached fromAntarctica and drifted north towardNorth America. It also allowed theAntarctic Circumpolar Current to flow, rapidly cooling the continent.
TheNeogene Period is a unit ofgeologic time starting 23.03 Ma.[10] and ends at 2.588 Ma. The Neogene Period follows thePaleogene Period. The Neogene consists of theMiocene andPliocene and is followed by theQuaternary Period.
TheMiocene extends from about 23.03 to 5.333 million years ago.[10]
During theMiocene continents continued to drift toward their present positions. Of the modern geologic features, only the land bridge betweenSouth America andNorth America was absent, the subduction zone along thePacific Ocean margin of South America caused the rise of theAndes and the southward extension of theMeso-American peninsula.India continued to collide withAsia. The Tethys Seaway continued to shrink and then disappeared asAfrica collided withEurasia in theTurkish-Arabian region between 19 and 12Ma (ICS 2004). Subsequent uplift of mountains in the westernMediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea resulting in theMessinian salinity crisis near the end of the Miocene.
ThePliocene extends from5.333 million years ago to2.588 million years ago.[10] During thePliocene 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 theIsthmus of Panama during the Pliocene, bringing a nearly complete end to South America's distinctivemarsupial 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 withEurope formed theMediterranean Sea, cutting off the remnants of theTethys Ocean. Sea level changes exposed the land-bridge betweenAlaska and Asia. Near the end of the Pliocene, about2.58 million years ago (the start of the Quaternary Period), thecurrent ice age began. The polar regions have since undergone repeated cycles of glaciation and thaw, repeating every 40,000–100,000 years.
ThePleistocene extends from2.588 million years ago to 11,700 years before present.[10] The moderncontinents were essentially at their present positions during thePleistocene, theplates upon which they sit probably having moved no more than 100 kilometres (62 mi) relative to each other since the beginning of the period.
TheHolocene Epoch began approximately 11,700 calendar years before present[10] and continues to the present. During theHolocene, continental motions have been less than a kilometer.
Thelast glacial period of thecurrent ice age ended about 10,000 years ago.[55] Ice melt caused worldsea levels to rise about 35 metres (115 ft) in the early part of the Holocene. In addition, many areas above about40 degrees north latitude had been depressed by the weight of the Pleistoceneglaciers 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 fromVermont,Quebec,Ontario andMichigan. 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 inScandinavia resulted in the emergence of coastal areas around theBaltic Sea, including much ofFinland. The region continues to rise, still causing weakearthquakes acrossNorthern Europe. The equivalent event in North America was the rebound ofHudson Bay, as it shrank from its larger, immediate post-glacialTyrrell Sea phase, to near its present boundaries.
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