The Four Eras of the Geologic Time Scale
- Precambrian Time: 4.6 billion to 542 Million Years Ago. Precambrian Time started at the beginning of the Earth 4.6 billion years ago. ...
- Paleozoic Era: 542 Million to 250 Million Years Ago. ...
- Mesozoic Era: 250 Million to 65 Million Years Ago. ...
- Cenozoic Era: 65 Million Years Ago to the Present. ...
What are the 12 geologic time periods?
What are the 12 geologic time periods? The names of the eras in the Phanerozoic eon (the eon of visible life) are the Cenozoic ("recent life"), Mesozoic ("middle life") and Paleozoic ("ancient life"). The further subdivision of the eras into 12 "periods" is based on identifiable but less profound changes in life-forms. Click to see full answer.
What are the 4 geological eons?
- Precambrian.
- Geochronology.
- Tertiary Period.
- Silurian Period.
- Earth.
- Devonian Period.
- Cambrian Period.
- Triassic Period.
What are the 4 eras of Earth?
The four eras that make up the geologic time scale are:
- Precambrian Era: This is the first era of the earth’s history and it is also the longest. ...
- Paleozoic Era: The 400 million years following the Precambrian Era make up the Paleozoic Era. ...
- Mesozoic Era: This era was dominated by the dinosaurs. ...
- Cenozoic Era: Since the end of the Mesozoic Era, the earth has existed within the Cenozoic Era. ...
What does the geologic time scale represent?
What is the Geologic Time Scale? What does the time scale represent? The geologic time scale divides up the history of the earth based on life-forms that have existed during specific times since the creation of the planet. These divisions are called geochronologic units (geo: rock, chronology: time).
What are the 4 ERAS from oldest to youngest?
The four main ERAS are, from oldest to youngest: PreCambrian, Palaeozoic, Mesozoic and Cenozoic.
What are the 4 ERAS of Earth history?
Earth's history is characterized by four eons; in order from oldest to youngest, these are the Hadeon, Archean, Proterozoic, and Phanerozoic.
How many geological eras are there?
Ten eras are recognized by the International Union of Geological Sciences: the Eoarchean Era (4.0 billion to 3.6 billion years ago), the Paleoarchean Era (3.6 billion to 3.2 billion years ago), the Mesoarchean Era (3.2 billion to 2.8 billion years ago), the Neoarchean Era (2.8 billion to 2.5 billion years ago), the ...
How many eras are there in history?
History is divided into three separate eras: Ancient Period – 3600 BC – 500 AD. Middle Ages – 500 AD – 1500 AD. Modern Era – 1500 – present.
What is the first era of Earth's history?
Precambrian. The Precambrian includes approximately 90% of geologic time. It extends from 4.6 billion years ago to the beginning of the Cambrian Period (about 539 Ma). It includes three eons, the Hadean, Archean, and Proterozoic.
What are the major eras?
Historians rely on written records and archaeological evidence to understand more about human history. They use these resources to divide human existence into five main historical eras: Prehistory, Classical, Middle Ages, Early Modern, and Modern eras.
What era are we currently in?
Cenozoic eraCurrently, we're in the Phanerozoic eon, Cenozoic era, Quaternary period, Holocene epoch and (as mentioned) the Meghalayan age.
What are the ages of the Earth?
4.543 billion yearsEarth / Age
What geologic period is the era of mammals?
Eons, eras, and periods are usually separated by a significant geologic event and are unique in their climate, landscape, and biodiversity. The Cenozoic era , for example, is known as the "Age of Mammals." The Carboniferous period, on the other hand, is named for the large coal beds that were formed during this time ("carboniferous" means coal-bearing). The Cryogenian period, as its name suggests, was a time of great glaciations.
When were the colors of the geologic time scale specified?
The dates shown on this geologic time scale were specified by the International Commission on Stratigraphy in 2015. The colors were specified by the Committee for the Geologic Map of the World in 2009.
What Is Geologic Dating?
Geologic dating allows scientists to better understand ancient history, including the evolution of plant and animal life from single-celled organisms to dinosaurs to primates to early humans. It also helps them learn more about how human activity has transformed the planet.
What era was the Neoarchean?
The Neoarchean, which began about 2.8 billion years ago, was the era in which oxygenic photosynthesis began. This process, performed by algae and other microorganisms, caused oxygen molecules in water to be released into the atmosphere. Prior to oxygenic photosynthesis, Earth's atmosphere had no free oxygen, a huge impediment to the evolution of life.
What is the most recent geologic eon?
The most recent geologic eon is the Phanerozoic, which began about 540 million years ago. This eon is very distinct from the previous three—the Hadean, Archean, and Proterozoic—which are sometimes known as the Precambrian era. During the Cambrian period—the earliest part of the Phanerozoic —the first complex organisms appeared. Most of them were aquatic; the most famous examples are trilobites, small arthropods (creatures with exoskeletons) whose distinct fossils are still being discovered today. During the Ordovician period, fish, cephalopods, and corals first appeared; over time, these creatures eventually evolved into amphibians and dinosaurs.
How are eons divided?
Eons are divided into eras, which are further divided into periods, epochs, and ages. Geologic dating is extremely imprecise. For example, although the date listed for the beginning of the Ordovician period is 485 million years ago, it is actually 485.4 with an uncertainty (plus or minus) of 1.9 million years.
What is the oldest eon?
Hadean. The oldest of the geologic eons is the Hadean, which began about 4.6 billion years ago with the formation of Earth and ended about 4 billion years ago with the appearance of the first single-celled organisms.
How many timelines show the geologic time scale?
The following five timelines show the geologic time scale. The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. Therefore, the second timeline shows an expanded view of the most recent eon. In a similar way, the most recent era is expanded in the third timeline, the most recent period is expanded in the fourth timeline, and the most recent epoch is expanded in the fifth timeline.
Who first proposed the geologic time scale?
Avicenna also first proposed one of the principles underlying geologic time scales, the law of superposition of strata, while discussing the origins of mountains in The Book of Healing (1027). The Chinese naturalist Shen Kuo (1031–1095) also recognized the concept of " deep time ".
What is the Hadean eon?
The Hadean eon represents the time before the fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga ( billion years ago). Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon.
How long is the Phanerozoic eon?
This is not to scale, and even though the Phanerozoic eon looks longer than the rest, it merely spans 500 million years, whilst the previous three eons (or the Precambrian supereon) collectively span over 3.5 billion years. This bias toward the most recent eon is due to the relative lack of information about events that occurred during the first three eons (or supereon) compared to the current eon (the Phanerozoic).
What is the largest division of time?
The primary and largest catalogued divisions of time are periods called eons . The first eon was the Hadean, starting with the formation of the Earth and lasting over 600 million years until the Archean eon, which is when the Earth had cooled enough for continents and the earliest known life to emerge.
How old is the Earth?
Evidence from radiometric dating indicates that Earth is about 4.54 billion years old. The geology or deep time of Earth's past has been organized into various units according to events that are thought to have taken place. Different spans of time on the GTS are usually marked by corresponding changes in the composition of strata which indicate major geological or paleontological events, such as mass extinctions. For example, the boundary between the Cretaceous period and the Paleogene period is defined by the Cretaceous–Paleogene extinction event, which marked the demise of the non-avian dinosaurs as well as many other groups of life. Older time spans, which predate the reliable fossil record (before the Proterozoic eon ), are defined by their absolute age.
Who established the primary principles of geology?
Establishment of primary principles. In the late 17th century Nicholas Steno (1638–1686) pronounced the principles underlying geologic (geological) time scales. Steno argued that rock layers (or strata) were laid down in succession and that each represents a "slice" of time.
