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The Mesozoic era saw the rise of some of the most iconic animals, from Tyrannosaurus rex to birds and mammals.

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Create a Canva Poster/Infographic About Your Assigned Era!

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Create a Canva Poster/Infographic About Your Assigned Era!

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Your poster/infographic should include the following: Name of your Era, 2 pictures/images, 3 facts

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Precambrian, period of time extending from about 4.6 billion years ago (the point at which Earth began to form) to the beginning of the Cambrian Period, 541 million years ago. The Precambrian encompasses the Archean and Proterozoic eons, which are formal geologic intervals that lasted from 4 billion to about 541 million years ago, and the Hadean Eon, which is an informal interval spanning from 4.6 billion to 4 billion years ago. The Precambrian represents more than 80 percent of the total geologic record.

All life-forms were long assumed to have originated in the Cambrian, and therefore all earlier rocks were grouped together into the Precambrian. Although many varied forms of life evolved and were preserved extensively as fossil remains in Cambrian sedimentary rocks, detailed mapping and examination of Precambrian rocks on most continents have revealed that additional primitive life-forms existed approximately 3.5 billion years ago. Nevertheless, the original terminology to distinguish Precambrian rocks from all younger rocks is still used for subdividing geologic time.

The earliest evidence for the advent of life includes Precambrian microfossils that resemble algae, cysts of flagellates, tubes interpreted to be the remains of filamentous organisms, and stromatolites (sheetlike mats precipitated by communities of microorganisms). In the late Precambrian, the first multicellular organisms evolved, and sexual division developed. By the end of the Precambrian, conditions were set for the explosion of life that took place at the start of the Cambrian, the first period of the Phanerozoic Eon (541 million years ago to the present).

The Precambrian environment

Several rock types yield information on the range of environments that may have existed during Precambrian time. Evolution of the atmosphere is recorded by banded-iron formations (BIFs), paleosols (buried soil horizons), and red beds, whereas tillites ( sedimentary rocks formed by the lithification of glacial till) provide clues to the climatic patterns that occurred during Precambrian glaciations.

One of the most important factors controlling the nature of sediments deposited today is continental drift. The continents are distributed at different latitudes, and latitudinal position affects the temperature of oceanic waters along continental margins (the combined area of the continental shelf and continental slope); in short, sedimentary deposition is climatically sensitive. At present, most carbonates and oxidized red soils are deposited within 30 degrees of the Equator, phosphorites within 45 degrees, and evaporites within 50 degrees. Most fossil carbonates, evaporites, phosphorites, and red beds of Phanerozoic age dating back to the Cambrian have a similar bimodal distribution with respect to their paleoequators. If the uniformitarian principle that the present is the key to the past is valid (meaning the same geologic processes occurring today occurred in the past), then sediments laid down during the Precambrian would have likewise been controlled by the movement and geographic position of the continents. Thus, it can be inferred that the extensive evaporites dating to 3.5 billion years ago from the Pilbara region of Western Australia could not have been formed within or near the poles. It can also be inferred that stromatolite-bearing dolomites of Riphean rock, a sedimentary sequence spanning the period from 1.65 billion to 800 million years ago, were deposited in warm, tropical waters. Riphean rock is primarily located in the East European craton, which extends from Denmark to the Ural Mountains, and in the Siberian craton in Russia.

Today, phosphate sediments are deposited primarily along the western side of continents. This is the result of high biological productivity in nearby surface waters due to the upwelling of nutrient-rich currents that are moving toward the Equator. The major phosphorite deposits of the Aravalli mountain belt of Rajasthan in northwestern India, which date from the Proterozoic Eon, are associated with stromatolite-rich dolomites. They were most likely deposited on the western side of a continental landmass that resided in the tropics.

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Precambrian, period of time extending from about 4.6 billion years ago (the point at which Earth began to form) to the beginning of the Cambrian Period, approximately 541 million years ago. The Precambrian represents more than 80 percent of the total geologic record.

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Visit-Paleozoic Parks

Every park contains some slice of geologic time. Below, we highlight selected parks associated with Paleozoic Era. This is not to say that a particular park has only rocks from the specified period. Rather, rocks in selected parks exemplify a certain event or preserve fossils or rocks from a certain geologic age.

Alibates Flint Quarries National Monument, Texas-[Geodiversity Atlas] [Park Home]

Big South Fork National River and Recreation Area, Kentucky and Tennessee-[Geodiversity Atlas] [Park Home]

Bighorn Canyon National Recreation Area, Montana and Wyoming-[Geodiversity Atlas] [Park Home]

Blue Ridge Parkway, North Carolina and Virginia-[Geodiversity Atlas] [Park Home]

Canyonlands National Par, Utahk-[Geodiversity Atlas] [Park Home]

Carlsbad Caverns National Park, New Mexico-[Geodiversity Atlas] [Park Home]

Chickasaw National Recreation Area, Oklahoma-[Geodiversity Atlas] [Park Home]

Cumberland Gap National Historical Park, Virginia, Kentucky, and Tennessee-[Geodiversity Atlas] [Park Home]

Cuyahoga Valley National Park, Ohio-[Geodiversity Atlas] [Park Home]

Denali National Park, Alaska-[Geodiversity Atlas] [Park Home]

Dinosaur National Monument, Colorado and Utah-[Geodiversity Atlas] [Park Home]

Gates of the Arctic National Park and Preserve, Alaska-[Geodiversity Atlas] [Park Home]

Glacier Bay National Park, Alaska-[Geodiversity Atlas] [Park Home]

Glen Canyon National Recreation Area, Arizona and Utah-[Geodiversity Atlas] [Park Home]

Great Basin National Park, Nevada-[Geodiversity Atlas] [Park Home]

Great Smoky Mountains National Park, Tennessee and North Carolina-[Geodiversity Atlas] [Park Home]

Guadalupe Mountains National Park, Texas-[Geodiversity Atlas] [Park Home]

Harpers Ferry National Historical Park, Maryland, Virginia, and West Virginia-[Geodiversity Atlas] [Park Home]

Jewel Cave National Monument, South Dakota-[Geodiversity Atlas] [Park Home]

Katahdin Woods and Waters National Monument, Maine-[Geodiversity Atlas] [Park Home]

Natchez Trace Parkway, Alabama, Mississippi & Tennessee-[Geodiversity Atlas] [Park Home]

Natural Bridges National Monument, Utah-[Geodiversity Atlas] [Park Home]

New River Gorge National River, West Virginia-[Geodiversity Atlas] ]Park Home]

Noatak National Preserve, Alaska-[Geodiversity Atlas] [Park Home]

Obed Wild and Scenic Rive, Tennessee-[Geodiversity Atlas] [Park Home]

Ozark National Scenic Riverways, Missouri-[Geodiversity Atlas] [Park Home]

Parashant National Monument, Arizona-[Geodiversity Atlas] [Park Home]

Pictured Rocks National Lakeshore, Michigan-[Geodiversity Atlas] [Park Home]

Prince William Forest Park, Virginia-[Geodiversity Atlas] [Park Home]

Rock Creek Park, Washington D.C.-[Geodiversity Atlas] [Park Home]

Russell Cave National Monument, Alabama-[Geodiversity Atlas] [Park Home]

Saint Croix National Scenic Riverway, Minnesota and Wisconsin-[Geodiversity Atlas] [Park Home]

Shenandoah National Park, Virginia-[Geodiversity Atlas] [Park Home]

Upper Delaware Scenic & Recreational River, New York and Pennsylvania-[Geodiversity Atlas] [Park Home]

Walnut Canyon National Monument, Arizona-[Geodiversity Atlas] [Park Home]

Whiskeytown-Trinity-Shasta National Recreation Area, California-[Geodiversity Atlas] [Park Home]

Wrangell-St. Elias National Park and Preserve, Alaska-[Geodiversity Atlas] [Park Home]

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Paleozoic Era (U.S. National Park Service)

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Every park contains some slice of geologic time. Below, we highlight selected parks associated with Paleozoic Era. This is not to say that a particular park has only rocks from the specified period. Rather, rocks in selected parks exemplify a certain event or preserve fossils or rocks from a certain geologic age.

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Artist's conception of our solar system's solar nebula, the cloud of gas and dust from which the planets formed.

Credit: Painting copyright William K. Hartmann, Planetary Science Institute, Tucson

The Precambrian is the name given for the first super eon of Earth's history. This division of time - about seven-eighths of Earth's history - lasted from the first formation of the planet (about 4.6 billion years ago) to the geologically sudden diversification of multicellular life known as the Cambrian Explosion (usually dated at about 542 million years ago).

The Precambrian is usually considered to have three eons: the Hadean, the Archean and the Proterozoic. Some scientists recognize a fourth eon, which they call the Chaotian, which predates the others and is the time of the first formation of our solar system.

The Hadean Eon occurred 4.6 billion to 4 billion years ago. It is named for the mythological Hades, an allusion to the probable conditions of this time. During Hadean time, the solar system was forming within a cloud of dust and gas known as the solar nebula, which eventually spawned asteroids, comets, moons and planets.

Astrogeophysicists theorize that about 4.52 billion years ago the proto-Earth collided with a Mars-size planetoid named Theia. The collision added about 10 percent to Earth's mass. Debris from this collision coalesced to form Earth's moon. It is hypothesized that Theia's iron core sank to the center of the still molten Earth, giving this planet's core enough density to begin to cool. Lighter elements "floating" on the surface began to form a scum of crustal materials. This early crust was frequently turned and subsumed by the molten interior. There are few terrestrial rocks from Hadean time, just a few mineral fragments found in sandstone substrates in Australia. However, study of lunar formations shows that the Earth/moon system continued to be bombarded by frequent asteroid collisions throughout the Hadean.

Between 4 billion and 2.5 billion years ago, the continental shield rock began to form. Approximately 70 percent of continental landmass was formed during this time. Small "island" land masses floated in the molten "seas." Earth had acquired enough mass to hold a reducing atmosphere composed of methane, ammonia and other gases. Water from comets and hydrated minerals condensed in the atmosphere and fell as torrential rain, cooling the planet and filling the first oceans with liquid water.

Exactly when or how it happened is unknown, but microfossils of this time indicate that life began in the oceans about 3.5 billion to 2.8 billion years ago. It is probable that these microscopic prokaryotes began as chemoautotrophs, anaerobic bacteria able to obtain carbon from carbon dioxide (CO ₂). By the end of the Archean, the ocean floor was covered in a living mat of bacterial life.

The Proterozoic Eon is also called the Cryptozoic ("age of hidden life"). About 2.5 billion years ago, enough shield rock had formed to start recognizable geologic processes such as plate tectonics. Geology was about to be joined by biology to continue Earth's progress from a molten hell to a living planet. It is generally accepted that different types of prokaryotic organisms formed symbiotic relationships. Some types, more efficient at converting energy, were engulfed by larger protective "bubbles" able to shield them from the harsh environment. As time went on the symbiotic relationship became permanent and the "energy conversion" components became the chloroplasts and mitochondria of the first eukaryotic cells. Microfossils of these early cells are called Acritarchs.

About 1.2 billion years ago, plate tectonics forced the available shield rock to collide, forming Rodinia (a Russian term meaning "mother land"), Earth's first super continent. Rodinia's coastal waters were filled with rounded colonies of photosynthetic algae known as stromatolites. Photosynthesis began to add oxygen to the atmosphere, putting pressure on organisms adapted to the reduction atmosphere of the early Earth.

After a brief ice age in the mid-Proterozoic, organisms underwent rapid differentiation. The Ediacaran Period , the last of the Proterozoic Era, saw the first multicellular organisms. Autotrophs and soft-bodied heterotrophs filled the continental shelf regions around Rodinia. Many were Cnidarians similar to small jellyfish with radial body symmetry and specialized cells to sting prey and convey it into the body cavity. Fossils show that significantly different populations inhabited different localities. Some benthic (sea bottom-dwelling) organisms used a muscular "foot" to cling to the ocean bottom similar to the modern sea pen. Kimbrella fossils show a clear anterior/posterior axis, bilateral body symmetry and some indications they could crawl. Some scientists classify them as being related to the mollusks.

The boundary between the Ediacaran Period of the Proterozoic Era and the Cambrian Period of the Paleozoic Era is not as clear-cut as it was once thought to be. It used to be thought that increasing oxygenation caused a mass extinction of Ediacaran forms and a geologically sudden proliferation of new complex forms. Now it is understood that there were many complex multicellular animals capable of living in the higher oxygen of the Ediacaran environment. However they were nearly all soft-bodied forms, which left few fossil traces behind for us to find. The relative abundance of Cambrian fossils represents an increase in animals with calcified body parts, which were easily fossilized, not a mass extinction of Ediacaran life as was once thought.

Paleozoic Era: Facts & Information

Mesozoic Era: Age of the Dinosaurs

Cenozoic Era: Facts About Climate, Animals & Plants

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Precambrian: Facts About the Beginning of Time

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The Precambrian was the first super eon of Earth's history. This division of time - about seven-eighths of Earth's history - lasted from the first formation of the planet (about 4.6 billion years ago) to about 542 million years ago.

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Paleozoic Era, or Palaeozoic Era, Major interval of geologic time, c. 542-251 million years ago. From the Greek for "ancient life," it is the first era of the Phanerozoic Eon and is followed by the Mesozoic Era. It is divided into six periods: (from oldest to youngest) the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. During the early Paleozoic, much of North America was covered by a warm, shallow sea with many coral reefs. Fossils from this time include marine invertebrates and primitive fish; the plants were predominantly algae, with some mosses and ferns. During the late Paleozoic, huge, swampy forest regions covered much of the northern continents. Plant and animal life flourished. Amphibians left the oceans to live on land, reptiles evolved as fully terrestrial life-forms, and insect life began. Ferns grew to tree size, and precursors of the conifers appeared.

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Paleozoic Era, or Palaeozoic Era, Major interval of geologic time, c. 542-251 million years ago. From the Greek for "ancient life," it is the first era of the Phanerozoic Eon and is followed by the Mesozoic Era. It is divided into six periods: (from oldest to youngest) the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.

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In geologic time , Precambrian time encompasses the time from Earth's formation, approximately 4.5 billion years ago, until the start of the Cambrian approximately 540 million years ago (mya). Because the Precambrian is not a true geologic eon, era, period, or epoch, geologists often refer to it as Precambrian time (or simply, Precambrian). Precambrian time represents the vast bulk of Earth's geologic history and covers nearly 90% of Earth's history.

Although scientists do not yet know all the exact steps by which the earth formed, cooled, and took on its approximate shape and physical characteristics, a good deal of reliable evidence can be inferred from studies that concentrate on the formation of landmass, oceans , and atmosphere. Astrophysical dataand theories of physics that explain the evolution of physical law and nucelosynthesismake these studies of Earth's formation both possible and reliable because the same laws of physics and chemistry that exist now operated during the formation of Earth's solar system .

Radiological dating provides overwhelming evidence that dates known terrestrial (Earth origin) rock specimens to more than 3.6 billion years old. Earth and lunar meteorites date to 4.5 billion years.

Precambrian time is subdivided into Hadean time (4.5 billion years ago to 3.8 billion years ago); Archean time (3.8 billion years ago to 2.5 billion years ago; Paleoproterozoic time (2.5 billion years ago to 1.6 billion years ago); Mesoproterozoic time (1.6 billion years ago to 900 million years ago); and Neoproterozoic time (900 million years ago to 540 mya).

Hadean time represents the time during which the solar system formed. During the subsequent course of Precambrian time, Earth's lithospheric plates formed and the mechanisms of geologic change described by modern plate tectonic theory began to occur. During Precambrian time, life arose on Earth. The oldest known fossil evidence (fig tree group fossils in what is now Africa ) dates to early in Archaean time. During the Paleoproterozoic, Earth's primitive atmosphere made a transition to an oxygen rich atmosphere. Soon thereafter in geologic time, i.e. within a few hundred million years, there is evidence of the earliest appearance of eukaryotes (organisms with a true nucleus containing DNA). Evidence of the oldest fossilized animal remains dates to the end of Neoproterozic time.

The extensive debris field that existed in the early solar system assured frequent bombardment of Earth's primitive atmosphere by asteroids and comets . Despite the consuming effects of geological weathering and erosion , evidence of Precambrian time impacts dating almost 2.0 billion years ago have been found in what are now South Africa and Canada.

See also Cambrian Period; Cenozoic Era; Cretaceous Period; Dating methods; Devonian Period; Eocene Epoch; Evolution, evidence of; Fossil record; Fossils and fossilization; Historical geology; Holocene Epoch; Jurassic Period; Mesozoic Era; Miller-Urey experiment; Miocene Epoch; Mississippian Period; Oligocene Epoch; Ordovician Period; Paleocene Epoch; Paleozoic Era; Pennsylvanian Period; Phanerozoic Eon; Pleistocene Epoch; Pliocene Epoch; Precambrian; Proterozoic Era; Quaternary Period; Silurian Period; Tertiary Period; Triassic Period

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In geologic time , Precambrian time encompasses the time from Earth's formation, approximately 4.5 billion years ago, until the start of the Cambrian approximately 540 million years ago (mya). Because the Precambrian is not a true geologic eon, era, period, or epoch, geologists often refer to it as Precambrian time (or simply, Precambrian).

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In geologic time , the Mesozoic Era, the second era in the Phanerozoic Eon , spans the time between roughly 250 million years ago (mya) and 65 mya.

The Mesozoic Era contains three geologic time periods including the Triassic Period (250 mya to approximately 206 mya), Jurassic Period (206 mya to approximately 144 mya), and the Cretaceous Period (144 mya to 65 mya).

The Mesozoic Era begins at the end of the Permian Period of the Paleozoic Era . The Mesozoic Era's Cretaceous Period ends with the K-T boundary or K-T event .

During the Mesozoic Era the Pangaean supercontinent spanned Earth's equatorial regions and separated the Panthalassic Ocean and the Tethys Ocean basins. At the start of the Mesozoic Era there was little differentiation or separation between the continental crust that would eventually form the North American, European, South American, and African Continents.

Driven by plate tectonics , by the middle of the Mesozoic Era (approximately 170 mya) the North American and European continents diverged and the earliest form of the Atlantic Ocean emerged between the continents. At mid-Mesozoic Era, although still united along a broad region, what would become the South American and African Plates became distinguishable in a form similar to the modern continents. North America and South America remained united by a dry strip of land similar to the isthmus connection that exists today.

Late in the Mesozoic Era, an increase in sea level allowed the confluence of the now distinguishable Pacific Ocean and Atlantic Ocean to provide a wide water barrier between North and South America. Much of what are now the eastern and middle portions of the United States was flooded. By the end of the Mesozoic Era, water separated South America from Africa . The Australian and Antarctic continents were clearly articulated and the Antarctic continent began a southward migration to the south polar region.

The Mesozoic Era began with a mass extinction and ended with mass extinction. At the end of the Paleozoic Era, almost 80% of marine species became extinct. It would not be until well into the Mesozoic Era that marine life recovered and new reef-building corals evolved. Reptiles dominated the land. Accordingly, the Mesozoic Era is often termed "The Age of Reptiles."

Mesozoic essentially means "middle animals" and marked a fundamental high point in the number and types of species on Earth. Dinosaurs evolved to rule the Mesozoic Era but non-avian species of dinosaurs became extinct as part of the mass extinction that marked the end of the Mesozoic and start of the Cenozoic Era .

The landscape of the Mesozoic Era was also marked by substantial changes in vegetative patterns that altered erosional patterns involved in landscape evolution . During the Mesozoic Era, both gymnosperm (conifers, etc.) and subsequently angiosperm plants evolved in forms comparable to their modern form. Plant growth also allowed the subsequent development of extensive coal beds.

Like the Paleozoic, the Mesozoic Era closed with an episode of extinction. More than 70% of all existing life forms became extinct by the Mesozoic EraCenozoic Era boundary (also known as the Cretaceous-Tertiary boundary), including virtually all of the dinosaurs.

During the Mesozoic Era large meteor impacts were frequent. The impact at the start of the Mesozoic Era has been estimated to be of such force as to be able to creating a 350 km impact crater , The K-T event crater (i.e., the Chicxulub crater) measures 170 km in diameter.

See also Archean; Cambrian Period; Cenozoic Era; Dating methods; Devonian Period; Eocene Epoch; Evolution, evidence of; Fossil record; Fossils and fossilization; Geologic time; Historical geology; Holocene Epoch; Miocene Epoch; Mississippian Period; Oligocene Epoch; Ordovician Period; Paleocene Epoch; Pennsylvanian Period; Phanerozoic Eon; Pleistocene Epoch; Pliocene Epoch; Precambrian; Proterozoic Eon; Quaternary Period; Silurian Period; Supercontinents; Tertiary Period

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In geologic time , the Mesozoic Era, the second era in the Phanerozoic Eon , spans the time between roughly 250 million years ago (mya) and 65 mya. The Mesozoic Era contains three geologic time periods including the Triassic Period (250 mya to approximately 206 mya), Jurassic Period (206 mya to approximately 144 mya), and the Cretaceous Period (144 mya to 65 mya).

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Introduction

The Mesozoic Era (251.9 to 66.0 million years ago) was the "Age of Reptiles." During the Mesozoic, Pangaea began separating into the modern continents, and the modern Rocky Mountains rose. Dinosaurs, crocodiles, and pterosaurs ruled the land and air. As climate plate tectonics, sea levels rose world-wide and seas expanded across the center of North America. Large marine reptiles such as plesiosaurs, along with the coiled-shell ammonites, flourished in these seas. Common Mesozoic fossils include dinosaur bones and teeth, and diverse plant fossils.

Mesozoic Resources

The Mesozoic Era is further divided into three Periods: the Triassic, the Jurassic, and the Cretaceous. A few examples of NPS resources in each time Period are highlighted below.

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Mesozoic Era (U.S. National Park Service)

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The Mesozoic Era (251.9 to 66.0 million years ago) was the "Age of Reptiles." During the Mesozoic, Pangaea began separating into the modern continents, and the modern Rocky Mountains rose. Dinosaurs, crocodiles, and pterosaurs ruled the land and air. As climate plate tectonics, sea levels rose world-wide and seas expanded across the center of North America.

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Mesozoic Era, Second of the Earth's three major geologic eras and the interval during which the continental landmasses as known today were separated from the supercontinents Laurasia and Gondwana by continental drift. It lasted from c. 251 to c. 65.5 million years ago and includes the Triassic, Jurassic, and Cretaceous periods. The Mesozoic saw the evolution of widely diversified and advanced flora and fauna, quite different from those that had developed earlier during the Paleozoic Era or that would develop later during the Cenozoic Era.

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Mesozoic Era, Second of the Earth's three major geologic eras and the interval during which the continental landmasses as known today were separated from the supercontinents Laurasia and Gondwana by continental drift. It lasted from c. 251 to c. 65.5 million years ago and includes the Triassic, Jurassic, and Cretaceous periods.

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In geologic time , the Cenozoic Era, the third era in the Phanerozoic Eon , follows the Mesozoic Era and spans the time between roughly 65 million years ago (mya) and present day. On the geologic time scale, Earth is currently in the Cenozoic Era of the Phanerozoic Eon.

The Cenozoic Era contains two geologic time periods, including the Tertiary Period (65 mya to approximately 1.8 mya) and the current Quaternary Period (1.8 mya to present day). The Tertiary Period is also sometimes referred to in terms of a Paleogene Period and a Neogene Period. When referred to in terms of a Paleogene Period and a Neogene Period, the Paleogene Period extends from approximately 65 mya to 23 mya and the Neogene Period from 23 mya to 2.6 mya. The Quaternary Period is also termed the Anthropogene Period. These periods are further subdivided into six different major epochs, including the Paleocene Epoch , Oligocene Epoch , Miocene Epoch , and Pliocene Epoch , Pleistocene Epoch and current Holocene Epoch .

The onset of the Cenozoic Era is marked by the K-T boundary or K-T eventthe mass extinction of non-avian dinosaurs marking the boundary between the Cretaceous Period of the Mesozoic Era and the Tertiary Period of the Cenozoic Era.

At the start of the Cenozoic Era, North America and were separated by a widening ocean basin spreading along a prominent mid-oceanic ridge. North America and South America were separated by a confluence of the future Pacific Ocean and Atlantic Ocean, and extensive flooding submerged much of what are now the eastern and middle portions of the United States. By start of the Cenozoic Era, water separated South America from Africa , and seafloor spreading continued to push the continents apart. The Australian and Antarctic continents were clearly articulated and the Antarctic continent had begun a southward migration toward its present position in the south polar region. At the outset of the Cenozoic Era, the Indian plate and subcontinent remained far south of the Eurasian plate and continent.

By 30 mya, the modern continental arrangement was easily recognizable. Although still separated by water, the land bridge between North and South America began to reemerge. Antarctica assumed a polar position and extensive ice accumulation began on the continent. The Indian plate drove rapidly northward of the equator to close with the Eurasian plate. Although still separated by a shallow straight of water, the impending collision of the plates that would eventually form the Himalayan mountain chain had begun. The gap between North America and Europe continued to widen at a site of sea-floor spreading along a prominent mid-Atlantic ridge. By mid-Tertiary Period, the mid-Atlantic ridge was apparent in a large suture-like extension into the rapidly widening South Atlantic Ocean that separated South America from Africa.

Well into the Cenozoic Era, by the start of the Quaternary Period some 2.6 million years ago, Earth's continents assumed their modern configuration. The Pacific Ocean separated and from North America and South America, the Atlantic Ocean separated North and South America from Europe (Euro-Asia) and Africa. Separated by the straits of Indonesia, the Indian Ocean filled the basin between Africa, India, Asia, and Australia. The Indian plate driving against and under the Eurasian plate uplifted rapid mountain building. As a result of the collision, ancient oceanic crust bearing marine fossils was uplifted into the Himalayan chain. The collision between the Indian and Eurasian plate continues with a resulting slowbut measurableincrease in the altitude of the highest Himalayan Mountains (e.g., Mt. Everest) each year. Although glacial sheets advance and recede in cyclic patterns (i.e., reestablish new terrain altering ice ages, the basic patterns of glaciation evident today were established during the Quaternary Period.

Many geologists and paleontologists assert that the K-T extinction resulted from a cataclysmic asteroid impact in an area now located underwater near the Yucatan Peninsula of Mexico. The impact caused widespread primary damage due to the blast impact and firestorms. The major damage to Earth's ecosystem occurred when the debris and smoke from the collision and subsequent fires moved into the atmosphere to block a sufficient amount of light from the that photosynthesis was greatly slowed. The resulting climatic changes and food shortages led to extinction of the largest life forms (those with the greatest energy needs), including the dinosaurs.

Although mammals evolved before the Cenozoic Era, the reduction in predator species allowed land mammals to dominate and thriveeventually setting the stage from the evolution of homo sapiens (humans).

See also Archean; Cambrian Period; Dating methods; Devonian Period; Eocene Epoch; Evolution, evidence of; Fossil record; Fossils and fossilization; Geologic time; Historical geology; Jurassic Period; Mississippian Period; Ordovician Period; Paleozoic Era; Pennsylvanian Period; Precambrian; Proterozoic Era; Quaternary Period; Silurian Period; Supercontinents; Tertiary Period; Triassic Period

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Cenozoic era [1] In geologic time , the Cenozoic Era, the third era in the Phanerozoic Eon , follows the Mesozoic Era and spans the time between roughly 65 million years ago (mya) and present day. On the geologic time scale, Earth [2] is currently in the Cenozoic Era of the Phanerozoic Eon.

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In geologic time , the Paleozoic Era, the first era in the Phanerozoic Eon , covers the time between roughly 544 million years ago (mya) and until 245 mya.

The Paleozoic Era spans six geologic time periods including the Cambrian Period (544 to 500 mya); Ordovician Period (500 mya to 440 mya); Silurian (440 mya to 410 mya); Devonian (410 mya to 360 mya); and the Carboniferous Period (360 mya to 286 mya) (in many modern geological texts, especially those in the United States, the time of Carboniferous Period is covered by two alternate geologic periods, the Mississippian Period [360 mya to 325 mya] and the Pennsylvanian Period [325 mya to 286 mya]. The final geologic time period in the Paleozoic Era is the Permian Period (286 mya to 245 mya).

The onset of the Paleozoic Era is marked by the "Cambrian explosion," the sudden appearance of numerous fossils . Although life certainly started in Precambrian time, The start of the Paleozoic Era marks the point at which life developed to a variety or organisms capable of leaving fossils. Although fossilization is difficult under any circumstances, organisms with structures such as shells have a much greater chance of leaving fossilized remains than did single celled microorganisms.

The Paleozoic Era spanned that period of geologic time during which the evolution of the first invertebrates, vertebrates, terrestrial (land-based) plants, bony fish, reptiles, insects, etc. took place. The end of the Paleozoic Era (approximately 245 mya) marks the largest mass extinction of species in Earth's history. During this mass extinction an estimated 90% of all Earth's marine species suddenly became extinct.

Six major continental landmasses developed during the Paleozoic Era. Although not located in their present global positions, parts of the modern continents can be traced to these landmasses. For example, continental crust now located in the North American continent was located near the equator during the Paleozoic Era. The forces of plate tectonics were active, and not only moved the continents but helped shape the continental margins though uplift and subduction. Enormous changes on sea state relative to the continents meant extensive flooding, marine transgression , and marine regression that added large sedimentary deposits (e.g., large limestone deposits). The abundance of organic life provided the start for abundant coal formation during the Carboniferous Period ( Pennsylvanian Period and Mississippian Period).

See also Archean; Cenozoic Era; Cretaceous Period; Dating methods; Eocene Epoch; Evolution, evidence of; Fossil record; Fossils and fossilization; Historical geology; Holocene Epoch; Jurassic Period; Mesozoic Era; Miocene Epoch; Oligocene Epoch; Paleocene Epoch; Pennsylvanian Period; Pleistocene Epoch; Pliocene Epoch; Quaternary Period; Tertiary Period; Triassic Period

Pa·le·o·zo·ic / ˌpālēəˈzōik/ * adj. Geol. of, relating to, or denoting the era between the Precambrian eon and the ∎ [as n.] (the Paleozoic) the Mesozoic era. Formerly called primary. Paleozoic era or the system of rocks deposited during it.

Paleozoic See PALAEOZOIC.

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Paleozoic Era In geologic time , the Paleozoic Era, the first era in the Phanerozoic Eon , covers the time between roughly 544 million years ago (mya) and until 245 mya.

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The Paleozoic Era, which ran from 541 million to 251.9 million years ago, was a time of great change on Earth. The era began with the breakup of one supercontinent and the formation of another. Plants became widespread. And the first vertebrate animals colonized land.

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(Image: © Public domain.)

The Cenozoic era, which began about 65 million years ago and continues into the present, is the third documented era in the history of Earth. The current locations of the continents and their modern-day inhabitants, including humans, can be traced to this period.

The era began on a big down note, catching the tail end of the Cretaceous-Paleogene extinction event at the close of the Cretaceous period that wiped out the remaining non-avian dinosaurs.

The term Cenozoic, first spelled "Kainozoic," was originally used in an 1840 entry in the Penny Cyclopedia encyclopedia in an article written by British geologist John Phillips. The name is derived from the Greek phrase meaning "recent life."

The Cenozoic era is divided into three periods:

Paleogene period (65-23 million years ago), which consists of the Paleocene, Eocene and Oligocene epochs);

Neogene period (23-2.6 million years ago), which includes the Miocene and Pliocene epochs);

Quaternary period (2.6 million years ago to the present), consisting of the Pleistocene and Holocene epochs). While it is widely accepted that we are still in the Holocene epoch, some scientists argue that we have entered the Anthropocene epoch. In a 2010 article in the scientific journal Environmental Science & Technology, scientists made the case for a new epoch, blaming humans for causing a drastic shift in conditions.

Climate and geography

The global climate of the early portion of the Cenozoic period was much warmer than it is today, and the overall climate of the Earth was much more consistent regardless of proximity to the equator.

The most significant period of global warming, known as the Paleocene-Eocene Thermal Maximum, took place of 55.8 million years ago. It was followed by a long cool, dry period. The current global warming event has been set off primarily by human activity.

Each segment of the Cenozoic experienced different climates. During the Paleogene period, most of the Earth's climate was tropical. The Neogene period saw a drastic cooling, which continued into the Pleistocene epoch of the Quaternary period.

As for the changing landscape, the continents drifted apart during the Paleogene period, creating vast stretches of oceans. This had a significant impact on the climate and marine life surrounding each continent.

During the Pleistocene epoch, glaciers covered central North America, extending as far east as New York, south to Kansas and Nebraska and west to the northern West Coast. The Great Lakes were formed as the glaciers receded.

Several of the world's foremost mountain ranges, including the Alps, Himalayas and the Rocky Mountains, were formed during the Cenozoic era.

Life during the Cenozoic Era

The Cenozoic era is also known as the Age of Mammals because the extinction of many groups of giant mammals, allowing smaller species to thrive and diversify because their predators no longer existed. Due to the large span of time covered by the period, it is beneficial to discuss the animal population by the milestone of the era rather than in generalities.

The beginning of the Paleogene period was a time for the mammals that survived from the Cretaceous period. Later in this period, rodents and small horses, such as Hyracotherium, are common and rhinoceroses and elephants appear. As the period ends, dogs, cats and pigs become commonplace. Other than a few birds that were classified as dinosaurs, most notable the Titanis, the dinosaurs were gone. Large flightless birds, such as the Diatryma, thrived.

The Neogene period gives rise to early primates, including early humans. Bovids, including cattle, sheep, goats, antelope and gazelle, flourish during this period.

Cave lions, sabre-toothed cats, cave bears, giant deer, woolly rhinoceroses, and woolly mammoths were prevailing species of the Quaternary period.

Without the dinosaurs, plant life had an opportunity to flourish during the Cenozoic era. Nearly every plant living today had its roots in the Cenozoic era. During the early part of the era, forests overran most of North America. However, as the climate cooled forests died off, creating open land.

Due to the widening of the oceans, sharks, whales and other marine life proliferated. The Great Lakes that formed in the western United States during the Eocene epoch were the perfect home for bass, trout and other fresh-water species.

As the forests thinned, grasses began to spread out over the plains of North America and savannas covered the land in the middle of the continent. Among the common plant life were pines, mosses, oaks and grasses. Flowering plants and edible crops dominate the landscape in the later part of this era as humans cultivate the land.

Other time periods
Precambrian: Facts About the Beginning of Time Paleozoic Era: Facts & Information Mesozoic Era: Age of the Dinosaurs Cenozoic Era: Facts About Climate, Animals & Plants

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Kim Ann Zimmermann - Live Science Contributor

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Cenozoic Era: Facts About Climate, Animals & Plants

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(Image: © Public domain.) The Cenozoic era, which began about 65 million years ago and continues into the present, is the third documented era in the history of Earth. The current locations of the continents and their modern-day inhabitants, including humans, can be traced to this period.

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Visit-Cenozoic Parks

Every park contains some slice of geologic time. Here we highlight a few parks associated with Cenozoic Era. This is not to say that a particular park has only rocks from the specified period. Rather, rocks in selected parks exemplify a certain event or preserve fossils or rocks from a certain geologic age.

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Cenozoic Era (U.S. National Park Service)

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Every park contains some slice of geologic time. Here we highlight a few parks associated with Cenozoic Era. This is not to say that a particular park has only rocks from the specified period. Rather, rocks in selected parks exemplify a certain event or preserve fossils or rocks from a certain geologic age.

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Cenozoic Era, Third of the major eras of Earth history, and the interval of time during which the continents assumed their modern configurations and geographic positions. It was also the time when the Earth's flora and fauna evolved toward those of the present. The Cenozoic, from the Greek for "recent life," began c. 65.5 million years ago and is divided into three periods: the Paleogene (65.5-23 million years ago), Neogene (23-2.6 million years ago) and Quaternary (2.6 million years ago to the present).

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Cenozoic Era, Third of the major eras of Earth history, and the interval of time during which the continents assumed their modern configurations and geographic positions. It was also the time when the Earth's flora and fauna evolved toward those of the present. The Cenozoic, from the Greek for "recent life," began c.