Geology eras - Feb 15, 2018 · By looking at the layers beneath our feet, geologists have been able to identify and describe crucial episodes in life’s history. These key events frame the chapters in the story of life on ...

 
As of April 2022 there are currently ten defined eras/erathems, namely the Eoarchean, Paleoarchean, Mesoarchean, Neoarchean, Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Paleozoic, Mesozoic and Cenozoic, with none from the Hadean eon. A period is a major rank below an era … See more. Completed graph

Faunal succession: is the time arrangement of fossils in the geological record. Formations: are stratigraphic successions containing rocks of related geological age that formed within the same geological setting. Ga: is an abbreviation used for billions (thousand million) of years ago. Geochronology: is the study of the age of geological materials.-The basic units of the geologic time scale are periods, eras, and centuries.-Humans appeared during the Cenozoic era.-Scientists developed the geologic time scale as they studied rock layers and index fossils.-Precambrian time makes up 88 percent of Earth's history.-the first birds appeared during the Jurassic period.The Jurassic (/ dʒ ʊ ˈ r æ s ɪ k / juu-RASS-ik) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where …About the geologic time scale divisions. The geologic history of the Earth is broken up into hierarchical chunks of time. From largest to smallest, this hierarchy includes eons, eras, periods, epochs, and ages. All of these are displayed in the portion of the geologic time scale shown below. Eon.Start with a blank sheet of kraft paper the height of the blackboard. The most important divisions for students to focus on are the Eras. The Paleozoic , Mesozoic and Cenozoic …The temperature of a planet is linked with the diversity of life that it can support. MIT geologists have now reconstructed a timeline of the Earth’s temperature during the early Paleozoic era, between 510 and 440 million years ago — a pivotal period when animals became abundant in a previously microbe-dominated world.Aug 16, 2022 · The Mesozoic era, when dinosaurs ruled, is divided into the Triassic, Jurassic, and Cretaceous periods. You can look at how the different eras are divided in the geologic timeline shown. Each era is represented by a unique group of organisms that lived together during that time. Each era and period has been given a designated range of years. Devonian Period, in geologic time, an interval of the Paleozoic Era that follows the Silurian Period and precedes the Carboniferous Period, spanning between about 419.2 million and 358.9 million years ago.The Devonian Period is sometimes called the “Age of Fishes” because of the diverse, abundant, and, in some cases, bizarre types of …The Mesozoic Era, which means "middle animal life," is characterized by a different assemblage of fossils, including ammonites and dinosaurs. The Cenozoic Era, which means "modern animal life," is dominated by fossils of animal groups that still survive, such as mammals. The geologic eras are subdivided into smaller time units called periods.You might wish to start in the Cenozoic Era (65.5 million years ago to the present) and work back through time, or start with Hadean time (4.6 to 4 billion ...The Phanerozoic is the current and the latest of the four geologic eons in the Earth's geologic time scale, covering the time period from 538.8 million years ago to the present. It is the eon during which abundant animal and plant life has proliferated, diversified and colonized various niches on the Earth's surface, beginning with the Cambrian period …Earth sciences - Geologic Time, Age, Earth: By mid-century the fossiliferous strata of Europe had been grouped into systems arrayed in chronological order. The stratigraphic column, a composite of these systems, was pieced together from exposures in different regions by application of the principles of superposition and faunal sequence. Time elapsed during the formation of a system became ...The list of periods and events in climate history includes some notable climate events known to paleoclimatology.Knowledge of precise climatic events decreases as the record goes further back in time. The timeline of glaciation covers ice ages specifically, which tend to have their own names for phases, often with different names used for different parts of …The Quaternary ( / kwəˈtɜːrnəri, ˈkwɒtərnɛri / kwə-TUR-nə-ree, KWOT-ər-nerr-ee) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). [4] It follows the Neogene Period and spans from 2.58 million years ago to the present. [5]The Archean Eon (IPA: / ɑːr ˈ k iː ə n / ar-KEE-ən, also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history, preceded by the Hadean Eon and followed by the Proterozoic.The Archean represents the time period from (millions of years ago). The Late Heavy Bombardment is …Oct 19, 2023 · Earth has existed for 4.5 billion years. In that time, it has undergone amazing transformations as a variety of geologic processes have changed the planet. Have students read the introduction to the infographic. Ask students, “Why does the author use the word ‘complex’ to describe the history of Earth? A period is a large interval of time with a definite characteristic while an era is a long period of time marking the start and end of an important event. What is the longest era in history? The longest geologic era was the Precambrian. It began with the formation of the earth about 4.53 billion years ago, and ended about 542 million years…The geologic time scale divides Earth’s 4.6 billion-year story into grandly named chapters. Like nesting dolls, the chapters contain sub-chapters, which themselves contain sub-sub-chapters.Then students will write in the geologic eras, periods and epochs. Students will research when the corresponding fossils and dinosaurs were present in which ...Feb 15, 2018 · By looking at the layers beneath our feet, geologists have been able to identify and describe crucial episodes in life’s history. These key events frame the chapters in the story of life on ... Mar 8, 2020 · One important moment in geologic time was the transition from the Mesozoic era to the Cenozoic era about 65 million years ago. The change was spurred by the asteroid impact that eventually killed ... Mesozoic Era, second of Earth’s three major geologic eras of Phanerozoic time. Its name is derived from the Greek term for “middle life.” The Mesozoic Era began 252.2 million years ago, following the conclusion of the Paleozoic Era, and ended 66 million years ago, at the dawn of the Cenozoic Era.In this pack you will find information and activities to help your class grasp the concept of geological time, just how old our planet is, and just how young we ...Talca, formerly San Agustín de Talca, city, central Chile.It lies in the Central Valley near the Maule River.. Founded in 1692 by Tomás Marín de Poveda, it was destroyed by earthquakes in 1742 and 1928 and was completely rebuilt. It is now a major urban centre midway between Santiago, 160 miles (260 km) to the north-northeast, and Concepción.In 2010 it was again struck by an earthquake ...Precambrian Era The period of geologic time that ran from around the time of Earth’s formation, roughly 4.6 billion years ago, to 540 million years ago. During this period, complex life forms — organisms containing many cells — emerged. The later Precambrian, from about one billion years to 540 million years ago, is also called the ...The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet. Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs . Eon. 1Precambrian Toggle Precambrian subsection 1.1Hadean Eon 1.2Archean EonLab 7: Geologic Time Introduction Geological processes have affected the Earth since its inception 4.6 billion (4,600,000,000) years ago. It is difficult for us to imagine the vastness of time which 4.6 billion years represents, or to perceive the amount of time required for many geological processes to occur (e.g., formation of The period is the basic unit of geological time in which a single type of rock system is formed. Two or more periods comprise a geological Era. Two or more Eras form an Eon, the largest division of geologic time. Some periods are divided into epochs. The major periods in the geologic history of the Earth are (mya=million years ago): EON.What are the 6 eras of Earth? It is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. Name of a major division of geologic time from c. 5 billion to 570 million years ago. It is now usually divided into the Archean and Proterozoic eons.Jun 13, 2019 · geology The study of Earth’s physical structure and substance, its history and the processes that act on it. People who work in this field are known as geologists. Planetary geology is the science of studying the same things about other planets. Holocene The current period in geologic time. Meaning “entirely recent,” the Holocene began at ... No previous Montessori skills, training, or resources required!The Clock of Eras is a graphic aid used by Montessori to help us visualize geologic time by ...The BGS geological timechart provides colourful reference material for use in schools, colleges and at home, setting out the geological timescale and geochronological terms we use at BGS. You can browse the timechart …As of April 2022 there are currently ten defined eras/erathems, namely the Eoarchean, Paleoarchean, Mesoarchean, Neoarchean, Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Paleozoic, Mesozoic and Cenozoic, with none from the Hadean eon. A period is a major rank below an era … See moreSep 16, 2022 · Geologic Time . The geological time scale in Figure \(\PageIndex{1}\) is one of the crowning achievements of science in general and geology in particular. It is a reference and communication system for comparing rocks and fossils found throughout the world and is geology's equivalent of the periodic table of the elements. Geologic time, the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins with the Archean Eon (4.0 billion to 2.5 billion years ago) and continues to the present day. Modern geologic time scales also include the Hadean Eon (4.6 billion to 4.0 billion years ago). At GSA you'll find the resources, confidence, and connections you need to reach fulfilling new heights in your geoscience career.Noun. 1. geological era - a major division of geological time; an era is usually divided into two or more periods. era. geologic time, geological time - the time of the physical formation and development of the earth (especially prior to human history) eon, aeon - the longest division of geological time. geological period, period - a unit of ...Earth’s history is divided into a hierarchical series of smaller chunks of time, referred to as the geologic time scale. These divisions, in descending length of time, are called eons, eras, periods, epochs, and ages. These units are classified based on Earth’s rock layers, or strata, and the fossils found within them. From examining these ...25‏/07‏/2023 ... What would become the basement rocks of Florida were once part of other continents. During the early part of the Cenozoic Era, Florida was ...17‏/12‏/2022 ... From largest to smallest, the chapters are called eons, eras, periods, epochs and ages. ... geology as a science,” she said. It demands we ...16‏/10‏/2017 ... The geologic eras are subdivided into smaller time units called periods. The periods are also based upon changes from older to younger types ...shown on the poster.The largest time span of the geologic time scaleis the eon.It is an indefinitely long period of time that contains at least two eras.Geologic time is divided into two eons.The more ancient eon is called the Precambrian, and the more recent is the Phanerozoic.Each eon is subdivided into smaller spans called eras.The20‏/07‏/2018 ... The International Commission on Stratigraphy, or ICS, is the global governing body that formally names geological eras, associating each rock ...13‏/06‏/2019 ... After the Precambrian come the Paleozoic Era and Mesozoic Era. Last but not least is the Cenozoic (Sen-oh-ZOE-ik) Era, the one in which we live.May 15, 2022 · Continental Drift. Figure 18.12.1 Pangaea. A body of evidence, both geological and biological, supports the conclusion that 200 million years ago, at the start of the Mesozoic era, all the continents were attached to one another in a single land mass, which has been named Pangaea. The geologic time scale is divided into eons, eras, periods, epochs, and ages. Our activities, and the time scale for download above, focus primarily on two of those divisions most relevant for an introduction to geologic time: eras and periods. The beginning and end of each chunk of time in the geologic time scale is determined by when some ... Geology is an undergraduate degree program focusing on the Earth's physical structure, composition, and history. It encompasses various disciplines such as ...Mesozoic – The Mesozoic Era, also called the Age of Reptiles and the Age of Conifers, is the second-to-last era of Earth’s geological history, lasting from about 252 to 66 million years ago and comprising the Triassic, Jurassic and Cretaceous Periods. Occurred: 251.902 (+/- 0.24) million years ago – 65 million years ago. Continental Drift Figure 18.12.1 Pangaea. A body of evidence, both geological and biological, supports the conclusion that 200 million years ago, at the start of the Mesozoic era, all the continents were attached to one another in a single land mass, which has been named Pangaea.This drawing of Pangaea (adapted from data of R. S. Dietz and J. C. Holden) is based on a computer-generated fit of ...To memorize the Epochs of Cenozoic Era: Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene (or Recent): Pretty Eager Old Men Play Poker Hard. Pigeon Egg Omelets Make People Puke Heartily. Put Eggs On My Plate Please Homer. The missing Era: Precambrian. Archean, ProterozoicCretaceous Period, in geologic time, the last of the three periods of the Mesozoic Era. The Cretaceous began 145.0 million years ago and ended 66 million years ago; it followed the Jurassic Period and was succeeded by the Paleogene Period (the first of the two periods into which the Tertiary Period was divided).Geological Era. The inclusions are real “bottles” in which fluids have remained trapped even for millions of years and which can give information regarding the temperature, pressure, density, and composition of the fluids existing in that particular geological environment in past geological eras.The geologic time scale divides Earth’s 4.6 billion-year story into grandly named chapters. Like nesting dolls, the chapters contain sub-chapters, which themselves contain sub-sub-chapters.Terminology. The largest defined unit of time is the supereon composed of Eons.Eons are divided into Eras, which are in turn divided into Periods, Epochs and Stages.At the same time paleontologists define a system of faunal stages, of varying lengths, based on the kinds of animal fossils found there. In many cases, such faunal stages have been adopted in …Apr 28, 2023 · Fossils Through Geologic Time. Fossils are found in the rocks, museum collections, and cultural contexts of more than 260 National Park Service areas and span every period of geologic time from billion-year-old stromatolites to Ice Age mammals that lived a few thousand years ago. Visit the parks that preserve fossils from each major time period. era: [noun] a fixed point in time from which a series of years is reckoned.This era is commonly referred to as "the era of the dinosaurs" since they were the ones dominating the planet at that time. It is divided into three periods: ...The Geologic Time Scale is divided into four eons, ten eras, 22 periods, and several epochs and ages. Each eon, era, period, and epoch is defined by major geological or paleontological events. The eons are the Hadean, Archean, Proterozoic, and Phanerozoic. The Phanerozoic Eon is the eon of visible life, and is divided into three eras: the ...Geologic time, the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins with the Archean …Geological time scale. The vast expanse of geological time has been separated into eras, periods, and epochs. The numbers included below refer to the beginnings of the division in which the title appears. The numbers are in millions of years.The units form a hierarchy in which each type of unit encompasses one or more smaller units—an eon contains two or more eras; an era encompasses several periods; and a period includes epochs. More than 80 percent of the total geologic record is contained within an interval called Precambrian time.Paleozoic (541-252 million years ago) means ‘ancient life.’. The oldest animals on Earth appeared just before the start of this era in the Ediacaran Period, but scientists had not yet discovered them when the geologic timescale was made. Life was primitive during the Paleozoic and included many invertebrates (animals without backbones) and ... ... eras or time periods. Reference. Geological Time Scale. extinction. noun. process of complete disappearance of a species from Earth. geologic timeline. noun.The modern Geologic Time Scale as shown above is a compendium of both relative and absolute age dating and represents the most up-to-date assessment of Earth's history. Using a variety of techniques and dating methods, geologists have been able to ascertain the age of the Earth, as well as major eras, periods, and epochs within Earth's history.Apr 25, 2017 · The demise of species later created fossils, which scientists have since dug up and used to help them analyze the earth's geological eras. 10. Eoarchean (4-3.6 billion years ago) The Eoarchean (4-3.6 billion years ago) era was the earliest time on earth after the initial forming of our planet from the dust and gas that came from the sun. This ... Standard 8-2.4: Recognize the relationship among the units—era, epoch, and period—into which the geologic time scale is divided. Eons: Longest subdivision; based on the abundance of certain fossils Eras: Next to longest subdivision; marked by major changes in the fossil record Periods: Based on types of life existing at the timeOnline exhibits: Geologic time scale: Cenozoic Era. The Holocene Epoch. 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 Geologic Time Scale is a tool for understanding how the Earth formed and came to be the way it is today. This is a simplified answer leaving much to be explained. Geologic time takes in all that has happened on earth since the Archaen Eon about 4 billion years ago. Informally it goes back to the Hadean 4.6 billion years ago.Generally, the eras used to describe the modern Earth are the Quaternary geological era and the Cenozoic evolutionary era. In the future, there may also be a historical era that the current time period, the 21st century, will belong to.Continental Drift. Figure 18.12.1 Pangaea. A body of evidence, both geological and biological, supports the conclusion that 200 million years ago, at the start of the Mesozoic era, all the continents were attached to one another in a single land mass, which has been named Pangaea.The geologic time scale is divided into eons, eras, periods, epochs, and ages. Our activities, and the time scale for download above, focus primarily on two of those divisions most relevant for an introduction to geologic time: eras and periods. The beginning and end of each chunk of time in the geologic time scale is determined by when some ...Geologic time began ticking when Earth formed ~4.6 billion years ago. Scaling this large amount of time to our calendar year, each of the 12 months of the geologic calendar year represents 383 million years (4.6 billion / 12). ... The Cenozoic Era is in a fingerprint, and with a single stroke of a nail file, you eradicate human history (McPhee ...Although American biologist Eugene Stoermer coined the term in the late 1980s, Dutch chemist and Nobelist Paul Crutzen is largely credited with bringing public attention to it at a conference in 2000 as well as in a newsletter printed the same year. In 2008 British geologist Jan Zalasiewicz and his colleagues put forth the first proposal to …The Anthropocene (/ ˈ æ n θ r ə p ə ˌ s iː n, æ n ˈ θ r ɒ p ə-/ AN-thrə-pə-seen, an-THROP-ə-) [failed verification] is a proposed geological epoch dating from the commencement of significant human impact on Earth's geology and ecosystems, including, but not limited to, human-caused climate change. The nature of the effects of humans on Earth can be …The Eocene (IPA: / ˈ iː ə s iː n, ˈ iː oʊ-/ EE-ə-seen, EE-oh-) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era.The name Eocene comes from the Ancient Greek ἠώς (ēṓs, "dawn") and καινός (kainós, "new") and refers to the "dawn" of modern …Apr 16, 2022 · What are the 5 geological eras in order? Geological Eras. Cenozoic Era: Topic. Last major division of geologic time lasting from 65 million years ago to the present. … Mesozoic Era: Topic. [Gr.,=middle life], major division of geologic time (see Geologic Timescale, table) from 65 to 225 million years ago. … Paleozoic Era. … Precambrian ... The coastal plain is North Carolina's largest geologic region, accounting for about 45 percent of the state. During the Mesozoic era, the coastal plain was a broad sloping region well above sea level. Its loose soil continually eroded from rains and streams flowing toward the ocean. During the Cenozoic era and occasionally the Mesozoic era, …Standard 8-2.4: Recognize the relationship among the units—era, epoch, and period—into which the geologic time scale is divided. Eons: Longest subdivision; based on the abundance of certain fossils Eras: Next to longest subdivision; marked by major changes in the fossil record Periods: Based on types of life existing at the time The 'Age of Dinosaurs' (the Mesozoic Era) included three consecutive geologic time periods (the Triassic, Jurassic, and Cretaceous Periods). Different dinosaur species lived during each of these three periods. For example, the Jurassic dinosaur Stegosaurus had already been extinct for approximately 80 million years before the...A geologic era is a subdivision of geologic time that divides an Eon into smaller buckets. The Phanerozoic Eon is divided into three such timeframes: the ...Geology is the study of earth, the materials of which it is made, the structure of those materials and the effects of the natural forces acting upon them and is important to civil engineering because all work performed by civil engineers in...The Quaternary ( / kwəˈtɜːrnəri, ˈkwɒtərnɛri / kwə-TUR-nə-ree, KWOT-ər-nerr-ee) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). [4] It follows the Neogene Period and spans from 2.58 million years ago to the present. [5]The Geologic Time Scale is divided into four eons, ten eras, 22 periods, and several epochs and ages. Each eon, era, period, and epoch is defined by major geological or paleontological events. The eons are the Hadean, Archean, Proterozoic, and Phanerozoic. The Phanerozoic Eon is the eon of visible life, and is divided into three eras: the ...The students will also be interacting with their journals using INB templates for the geologic time scale. Each INB activity is designed to help students compartmentalize information for a greater understanding of the concept. The geologic time scale INB templates allow students to focus their notes on the Geologic Time Eras.Timeline of glaciation. Climate history over the past 500 million years, with the last three major ice ages indicated, Andean-Saharan (450 Ma), Karoo (300 Ma) and Late Cenozoic. A less severe cold period or ice age is shown during the Jurassic - Cretaceous (150 Ma). There have been five or six major ice ages in the history of Earth over the ...Devonian Period, in geologic time, an interval of the Paleozoic Era that follows the Silurian Period and precedes the Carboniferous Period, spanning between about 419.2 million and 358.9 million years ago.The Devonian Period is sometimes called the “Age of Fishes” because of the diverse, abundant, and, in some cases, bizarre types of …Paleozoic (541-252 million years ago) means ‘ancient life.’. The oldest animals on Earth appeared just before the start of this era in the Ediacaran Period, but scientists had not yet discovered them when the geologic timescale was made. Life was primitive during the Paleozoic and included many invertebrates (animals without backbones) and ... A remarkable feature of the table above is how often evolutionary changes coincided with geologic changes on the earth. But consider that changes in geology …

The BGS Geological Timechart is based on geochronology. This is the branch of earth sciences that deals with the concept of geological time and dating the sequence of events throughout the Earth’s history. Intervals of geological time are given formal names and grouped into a hierarchy according to their length (in decreasing time intervals .... Mass media in the 1920s

geology eras

The Cenozoic (/ ˌ s iː n ə ˈ z oʊ. ɪ k, ˌ s ɛ n-/ SEE-nə-ZOH-ik, SEN-ə-; lit. 'new life') is Earth's current geological era, representing the last 66 million years of Earth's history. It is characterised by the dominance of …The units form a hierarchy in which each type of unit encompasses one or more smaller units—an eon contains two or more eras; an era encompasses several periods; and a period includes epochs. More than 80 percent of the total geologic record is contained within an interval called Precambrian time.ice age, also called glacial age, any geologic period during which thick ice sheets cover vast areas of land. Such periods of large-scale glaciation may last several million years and drastically reshape surface features of entire continents. A number of major ice ages have occurred throughout Earth history. The earliest known took place …Earth has existed for 4.5 billion years. In that time, it has undergone amazing transformations as a variety of geologic processes have changed the planet. Have …Identify eons, eras, periods, and epochs on the time scale, and study the history and development of the geologic time scale. Updated: 03/19/2022 Table of ContentsThe Cenozoic, Mesozoic, and Paleozoic are the Eras of the Phanerozoic Eon. Names of units and age boundaries usually follow the Gradstein et al. (2012), Cohen et al. (2012), and Cohen et al. (2013, updated) compilations. Numerical age estimates and picks of boundaries usually follow the Cohen et al. (2013, updated) compilation. Paleozoic Era, also spelled Palaeozoic, major interval of geologic time that began 538.8 million years ago with the Cambrian explosion, an extraordinary diversification of marine animals, and ended about 252 million years ago with the end-Permian extinction, the greatest extinction event in Earth history. The major divisions of the Paleozoic Era, …Geology is an undergraduate degree program focusing on the Earth's physical structure, composition, and history. It encompasses various disciplines such as ...The geologic temperature record are changes in Earth's environment as determined from geologic evidence on multi-million to billion (10 9) year time scales. The study of past temperatures provides an important paleoenvironmental insight because it is a component of the climate and oceanography of the time.Noun. 1. geological era - a major division of geological time; an era is usually divided into two or more periods. era. geologic time, geological time - the time of the physical formation and development of the earth (especially prior to human history) eon, aeon - the longest division of geological time. geological period, period - a unit of ...Scientists have identified the geological site that they say best reflects a proposed new epoch called the Anthropocene — a major step toward changing the official timeline of Earth’s history ...The BGS Geological Timechart is based on geochronology. This is the branch of earth sciences that deals with the concept of geological time and dating the sequence of events throughout the Earth’s history. Intervals of geological time are given formal names and grouped into a hierarchy according to their length (in decreasing time intervals ...epoch, unit of geological time during which a rock series is deposited.It is a subdivision of a geological period, and the word is capitalized when employed in a formal sense (e.g., Pleistocene Epoch). Additional distinctions can be made by appending relative time terms, such as early, middle, and late.The use of epoch is usually restricted to divisions of the …Scientists have identified the geological site that they say best reflects a proposed new epoch called the Anthropocene — a major step toward changing the official timeline of Earth’s history ...To make geologic time easier to comprehend, geologists divided the 4.6 billion years of Earth’s history into units of time called eons. Then they further divided the eons into two or more eras, eras into two or more periods, periods into two or more epochs, and epochs into two or more ages. These units are called geochronologic units, (geo ....

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