The Geologic Timescale
THE GEOLOGIC TIMESCALE
Divisions of Geologic Time * Eras are subdivided into periods...periods are subdivided into epochs.
* Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.
FOUR Eras… * PRE-CAMBRIAN – 88% of earth’s history * Paleozoic (ancient life) * 544 million years ago…lasted 300 million yrs * Mesozoic (middle life) * 245 million years ago…lasted 180 million yrs * Cenozoic (recent life) * 65 million years ago…continues through present day
Today… * Today we are in the Holocene Epoch of the Quaternary Period of the Cenozoic Era.
Paleozoic Era (Ancient Life) * The Cambrian period is the 1st period of the Paleozoic Era. “Age of the Trilobites” * Explosion of life in the oceans began during this era. * Most of the continents were covered in warm, shallow seas. * Invertebrates were dominate - Trilobites * Fish emerged during this time * Fish led to the arrival of amphibians * The end of the Paleozoic era is called the “Age of Amphibians” * Early land plants including mosses, ferns and cone-bearing plants. * The early coal forming forests were also formed during this time.
* Much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during the Paleozoic. * The Cambrian (beginning) opened with the breakup of the world-continent Rodinia and closed with the formation of Pangaea, as the Earth's continents came together once again. * This event is thought to have caused the climate changes that led to mass extinction event. * The Appalachian mountains were formed during this time. * At the end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species and 70% of land animals. * Possible causes
Divisions of Geologic Time * Eras are subdivided into periods...periods are subdivided into epochs.
* Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.
FOUR Eras… * PRE-CAMBRIAN – 88% of earth’s history * Paleozoic (ancient life) * 544 million years ago…lasted 300 million yrs * Mesozoic (middle life) * 245 million years ago…lasted 180 million yrs * Cenozoic (recent life) * 65 million years ago…continues through present day
Today… * Today we are in the Holocene Epoch of the Quaternary Period of the Cenozoic Era.
Paleozoic Era (Ancient Life) * The Cambrian period is the 1st period of the Paleozoic Era. “Age of the Trilobites” * Explosion of life in the oceans began during this era. * Most of the continents were covered in warm, shallow seas. * Invertebrates were dominate - Trilobites * Fish emerged during this time * Fish led to the arrival of amphibians * The end of the Paleozoic era is called the “Age of Amphibians” * Early land plants including mosses, ferns and cone-bearing plants. * The early coal forming forests were also formed during this time.
* Much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during the Paleozoic. * The Cambrian (beginning) opened with the breakup of the world-continent Rodinia and closed with the formation of Pangaea, as the Earth's continents came together once again. * This event is thought to have caused the climate changes that led to mass extinction event. * The Appalachian mountains were formed during this time. * At the end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species and 70% of land animals. * Possible causes