Geology chapter 19 – Flashcards

The Phanerozoic Eon spans 542 million years and is typically subdivided into three eras: Paleozoic Era: 542 to 251 million years ago. Mesozoic Era: 251 to 65 million years ago. Cenozoic Era: 65 million years ago to present.

The Cenozoic Era is generally divided into three periods: the Paleogene (66 million to 23 million years ago), the Neogene (23 million to 2.6 million years ago), and the Quaternary (2.6 million years ago to the present); however, the era has been traditionally divided into the Tertiary and Quaternary periods

Quaternary, the most recent 2.6 million years of Earth's history. Glaciers advance from the Poles and then retreat, carving and molding the land with each pulse. Sea levels fall and rise with each period of freezing and thawing. Some mammals get massive, grow furry coats, and then disappear. Humans evolve to their modern form, traipse around the globe, and make a mark on just about every Earth system, including the climate. At the start of the Quaternary, the continents were just about where they are today, slowing inching here and there as the forces of plate tectonics push and tug them about. But throughout the period, the planet has wobbled on its path around the sun. The slight shifts cause ice ages to come and go. By 800,000 years ago, a cyclical pattern had emerged: Ice ages last about 100,000 years followed by warmer interglacials of 10,000 to 15,000 years each. The last ice age ended about 10,000 years ago. Sea levels rose rapidly, and the continents achieved their present-day outline.

The Neogene is a geologic period and system in the International Commission on Stratigraphy (ICS) Geologic Timescale starting 23.03 million years ago and ending 2.58 million years ago. The second period in the Cenozoic Era, it follows the Paleogene Period and is succeeded by the Quaternary Period.

At the dawn of the Paleogene—the beginning of the Cenozoic era—dinosaurs, pterosaurs, and giant marine reptiles were conspicuously absent from the face of the Earth. Rodent-size (and perhaps larger) mammals emerged from the shadow of the night, suddenly free to fill the void. Over the next 42 million years, they grew in size, number, and diversity. As the period came to a close, life-forms still common today filled the seas, dominated the land, and had taken to the air. During the Paleogene the continents drifted farther apart, heading toward their modern positions. Oceans widened the gaps, Europe severed its last ties with North America, and Australia and Antarctica finally parted ways. As the climate significantly cooled and dried, sea levels continued to drop from late Cretaceous levels, draining most interior seaways. The cooling and drying trend began in earnest following a sudden temperature spike about 55 million years ago. Sea surface temperatures rose between 9 and 14 degrees Fahrenheit (5 and 8 degrees Celsius) over a period of a few thousand years, killing off numerous single-celled marine organisms called foraminifera, along with some other invertebrates. This event also profoundly affected northern forests, previously full of deciduous hardwoods with sequoias and pines. The new, more humid subtropical conditions nurtured abundant palms and guavas. Land mammals responded in kind, radiating and diversifying into many new forms. As the climate cooled and dried following the warming, forests gave way to open woodlands and grasslands in the northern hemisphere and started to support thundering herds of grazing mammals.

To observe a Holocene environment, simply look around you! The Holocene is the name given to the last 11,700 years* of the Earth's history — the time since the end of the last major glacial epoch, or "ice age." Since then, there have been small-scale climate shifts — notably the "Little Ice Age" between about 1200 and 1700 A.D. — but in general, the Holocene has been a relatively warm period in between ice ages.Another name for the Holocene that is sometimes used is the Anthropogene, the "Age of Man." This is somewhat misleading: humans of our own subspecies, Homo sapiens, had evolved and dispersed all over the world well before the start of the Holocene. Yet the Holocene has witnessed all of humanity's recorded history and the rise and fall of all its civilizations. Humanity has greatly influenced the Holocene environment; while all organisms influence their environments to some degree, few have ever changed the globe as much, or as fast, as our species is doing. The vast majority of scientists agree that human activity is responsible for "global warming," an observed increase in mean global temperatures that is still going on. Habitat destruction, pollution, and other factors are causing an ongoing mass extinction of plant and animal species; according to some projections, 20% of all plant and animal species on Earth will be extinct within the next 25 years. Yet the Holocene has also seen the great development of human knowledge and technology, which can be used — and are being used — to understand the changes that we see, to predict their effects, and to stop or ameliorate the damage they may do to the Earth and to us. Paleontologists are part of this effort to understand global change. Since many fossils provide data on climates and environments of the past, paleontologists are contributing to our understanding of how future environmental change will affect the Earth's life

This mammoth (right), found in deposits in Russia, was one of the largest land mammals of the Pleistocene, the time period that spanned from 2.6 million to 11,700 years ago.* Pleistocene biotas were extremely close to modern ones — many genera and even species of Pleistocene conifers, mosses, flowering plants, insects, mollusks, birds, mammals, and others survive to this day. Yet the Pleistocene was also characterized by the presence of distinctive large land mammals and birds. Mammoths and their cousins the mastodons, longhorned bison, saber-toothed cats, giant ground sloths, and many other large mammals characterized Pleistocene habitats in North America, Asia, and Europe. Native horses and camels galloped across the plains of North America. Great teratorn birds with 25-foot wingspans stalked prey. Around the end of the Pleistocene, all these creatures went extinct (the horses living in North America today are all descendants of animals brought from Europe in historic times).

Grazing mammals, such as the perissodactyls and artiodactyls diversified in the Miocene and Pliocene as grasslands and savanna spread across most continents. The Pliocene, 5.3 to 2.6 million years ago,* was a time of global cooling after the warmer Miocene. The cooling and drying of the global environment may have contributed to the enormous spread of grasslands and savannas during this time. The change in vegetation undoubtedly was a major factor in the rise of long-legged grazers who came to live in these areas. Additionally, the Panamanian land-bridge between North and South America appeared during the Pliocene, allowing migrations of plants and animals into new habitats. Of even greater impact was the accumulation of ice at the poles, which would lead to the extinction of most species living there, as well as the advance of glaciers and ice ages of the Late Pliocene and the following Pleistocene.

Miocene Epoch, SmilodonCourtesy of the American Museum of Natural History, New York earliest major worldwide division of the Neogene Period (23 million years to 2.6 million years ago) that extended from 23 million to 5.3 million years ago. It is often divided into the Early Miocene Epoch (23 million to 16 million years ago), the Middle Miocene Epoch (16 million to 11.6 million years ago), and the Late Miocene Epoch (11.6 million to 5.3 million years ago). The Miocene may also be divided into six ages and their corresponding rock stages: from oldest to youngest these ages or stages are the Aquitanian, Burdigalian, Langhian, Serravallian, Tortonian, and Messinian. The Miocene followed the Oligocene Epoch of the Paleogene Period and was succeeded by the Pliocene Epoch

The Oligocene epoch (39 to 22 million years ago) is the transition period between the earlier and later Tertiary period (65 to 2 million years ago).

The Eocene is the second of five epochs in the Tertiary Period — the second of three epochs in the Paleogene — and lasted from about 55.8 to 33.9 million years ago.* The oldest known fossils of most of the modern orders of mammals appear in a brief period during the early Eocene and all were small, under 10 kg. Both groups of modern ungulates, Artiodactyla and Perissodactyla, became prevalent mammals at this time, due to a major radiation between Europe and North America

The Paleocene (/ˈpæliɵsiːn//ˈpeɪliɵsiːn/[2] or Palaeocene, the "old recent", is a geologic epoch that lasted from about 66 to 56 million years ago. It is the first epoch of the Paleogene Period in the modern Cenozoic Era. As with many geologic periods, the strata that define the epoch's beginning and end are well identified, but the exact ages remain uncertain. The Paleocene Epoch brackets two major events in Earth's history. It started with the mass extinction event at the end of the Cretaceous, known as the Cretaceous-Paleogene (K-Pg) boundary. This was a time marked by the demise of non-avian dinosaurs, giant marine reptiles and much other fauna and flora. The die-off of the dinosaurs left unfilled ecological niches worldwide. It ended with the Paleocene-Eocene Thermal Maximum. This was a geologically brief (~0.2 million year) interval characterized by extreme changes in climate and carbon cycling.

The dinosaurs and the mammals appeared during the Triassic period, roughly 225 million years ago. The dinosaurs went extinct 65 million years ago. The Mesozoic Era lasted about 180 million years, and is divided into three periods, the Triassic, the Jurassic, and the Cretaceous.

The most famous of all mass extinctions marks the end of the Cretaceous Period, about 65 million years ago. As everyone knows, this was the great extinction in which the dinosaurs died out, except for the birds, of course

Great plant-eating dinosaurs roaming the earth, feeding on lush ferns and palm-like cycads and bennettitaleans ... smaller but vicious carnivores stalking the great herbivores ... oceans full of fish, squid, and coiled ammonites, plus great ichthyosaurs and long-necked plesiosaurs ... vertebrates taking to the air, like the pterosaurs and the first birds. This was the Jurassic Period, 199.6 to 145.5 million years ago* — a 54-million-year chunk of the Mesozoic Era

The Triassic Period was the first period of the Mesozoic Era and occurred between 251 million and 199 million years ago. It followed the great mass extinction at the end of the Permian Period and was a time when life outside of the oceans began to diversify.

The Paleozoic Era, which ran from about 542 million years ago to 251 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.

The Permian period lasted from 299 to 251 million years ago* and was the last period of the Paleozoic Era. The distinction between the Paleozoic and the Mesozoic is made at the end of the Permian in recognition of the largest mass extinction recorded in the history of life on Earth. It affected many groups of organisms in many different environments, but it affected marine communities the most by far, causing the extinction of most of the marine invertebrates of the time. Some groups survived the Permian mass extinction in greatly diminished numbers, but they never again reached the ecological dominance they once had, clearing the way for another group of sea life. On land, a relatively smaller extinction of diapsids and synapsids cleared the way for other forms to dominate, and led to what has been called the "Age of Dinosaurs." Also, the great forests of fern-like plants shifted to gymnosperms, plants with their offspring enclosed within seeds. Modern conifers, the most familiar gymnosperms of today, first appear in the fossil record of the Permian. The Permian was a time of great changes and life on Earth was never the same again.

The Carboniferous Period lasted from about 359.2 to 299 million years ago* during the late Paleozoic Era. The term "Carboniferous" comes from England, in reference to the rich deposits of coal that occur there

The Permian period lasted from 299 to 251 million years ago* and was the last period of the Paleozoic Era. The distinction between the Paleozoic and the Mesozoic is made at the end of the Permian in recognition of the largest mass extinction recorded in the history of life on Earth. It affected many groups of organisms in many different environments, but it affected marine communities the most by far, causing the extinction of most of the marine invertebrates of the time. Some groups survived the Permian mass extinction in greatly diminished numbers, but they never again reached the ecological dominance they once had, clearing the way for another group of sea life. On land, a relatively smaller extinction of diapsids and synapsids cleared the way for other forms to dominate, and led to what has been called the "Age of Dinosaurs." Also, the great forests of fern-like plants shifted to gymnosperms, plants with their offspring enclosed within seeds. Modern conifers, the most familiar gymnosperms of today, first appear in the fossil record of the Permian. The Permian was a time of great changes and life on Earth was never the same again.

The Carboniferous Period lasted from about 359.2 to 299 million years ago* during the late Paleozoic Era. The term "Carboniferous" comes from England, in reference to the rich deposits of coal that occur there

The Pennsylvanian (also known as Upper Carboniferous or Late Carboniferous) is, in the ICS geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period. It lasted from roughly 323.2 million years ago to 298.9 million years ago Ma (million years ago).

The Mississippian (also known as Lower Carboniferous or Early Carboniferous) is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earliest/lowermost of two subperiods of the Carboniferous period lasting from roughly 358.9 to 323.2 million years ago.

The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 419.2 Mya (million years ago), to the beginning of the Carboniferous Period, about 358.9.[5] It is named after Devon, England, where rocks from this period were first studied. The Devonian period experienced the first significant adaptive radiation of terrestrial life. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the "Age of Fish". The first ray-finned and lobe-finned bony fish appeared, while the placoderms began dominating almost every known aquatic environme

The Paleozoic era's Silurian period saw animals and plants finally emerge on land. ... The growth of corals and other marine organisms was stoked by oceans teeming with tiny planktonic creatures. ... While these fish, the first true jawed fish, reached no great size during the Silurian

During the Ordovician period, part of the Paleozoic era, a rich variety of marine life flourished in the vast seas and the first primitive plants began to appear on land—before the second largest mass extinction of all time ended the period. ... But once Gondwana took up its polar

The Cambrian Period marks an important point in the history of life on Earth; it is the time when most of the major groups of animals first appear in the fossil ... Trilobites were the dominant species during the Cambrian Period, 540 to 490 million years ago. ... The Cambrian Period is the first geological time period of the Paleozoic Era (the "time of ancient life"). ... The end of the Cambrian Period is marked by evidence in the fossil record of

The Precambrian covers almost 90% of the entire history of the Earth. It has been divided into three eras: the Hadean, the Archean and the Proterozoic. The Precambrian Era comprises all of geologic time prior to 600 million years ago.

The Proterozoic Eon extended from 2500 Ma to 542.0±1.0 Ma (million years ago), and is the most recent part of the Precambrian. It is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic

The Archean Eon (/ɑrˈkiːən/, also spelled Archaean) is a geologic eon, 4,000 to 2,500 million years ago, following the Hadean Eon and preceding the Proterozoic Eon

The Hadean Eon of geologic time began with the birth of the solar system, including our planet, Earth, and ended with the formation of the oldest rocks that are still preserved on the surface of Earth. The Hadean is the first period in Earth history, but one for which we have little record