Presentation on theme: "Geologic Time Linda Kennedy, Department of Geography, UNCG, July 2011 An Introduction."— Presentation transcript:
Geologic Time Linda Kennedy, Department of Geography, UNCG, July 2011 An Introduction
Age (millions)EraPeriod 2CenozoicQuaternary 66Tertiary 144MesozoicCretaceous 208Jurassic 245Triassic 286PaleozoicPermian 320Pennsylvanian 360Mississippian 408Devonian 438Silurian 505Ordovician 570Cambrian 4,500Precambrian Earth is how old? Our planet formed approximately 4.5 billion years ago (4,500,000,000). Geologists divide this immense length of time into progressively smaller (and more manageable) units of time using fossils, radiometric dating, and rock sequences. We will discuss the major characteristics of the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras. Geologic Time theres just so much of it!
Geologic Time theres just so much of it! History written in stone Evidence from rocks allows geologists: To identify the geological processes that resulted in the formation of each rock. To reconstruct atmospheric/climatic conditions and changes through time. To reconstruct plant/and or animal life prevalent during the formation of rocks
It is very difficult for humans to conceptualize a time frame as large as 4,500,000,000 years. To help we will imagine that Earth formed at 9:00 am this morning and it is now only10:00 am. What has occurred on planet Earth during the past hour? Geologic Time theres just so much of it! Present
Precambrian 9:00 – 9:53 The Precambrian Era 4.5 billion – 570 million years ago
Most of the past hour – 53 minutes –is known as the Precambrian era. Earths crust formed at approximately 9:01 but much of it has been recycled or altered from its original state (metamorphosed). Precambrian rock in North Carolina is located in the western portion of the state, in the Blue Ridge Mountains and includes granites, gneisses, and schists. Granite is magma that cooled deep in the crust and schist and gneiss are examples of rocks that have been heated and pressurized, altering their original form. Life during the Precambrian included single-celled, and simple multi-celled organisms. The Precambrian Era 4.5 billion – 570 million years ago
The Precambrian Era 4.5 billion – 570 million years ago Banded iron is believed to have formed when oxygen released by blue green algae combined with iron present in ancient ocean waters to form iron oxide precipitates that settled to the ocean floor. Stromatolites are dome shaped mineral formations built by microbes. They continue to survive today in the waters around Australia. Fossil stromatolites are one of the most common forms of fossil life identified in Precambrian rocks.
The Precambrian Era 4.5 billion – 570 million years ago Mount Airy, Surry Co. The worlds largest open faced granite mine. The granite formed when magma cooled deep in the crust. Overlying rock has since been eroded away, exposing the granite. Rock formed during the Precambrian is a valuable resource in North Carolina North Carolina is the nations top producer of mica, a mineral used in a variety of industries. Mica
Paleozoic 9:53 – 9:56.9 The Paleozoic Era old life 570 – 245 million years ago
The Paleozoic Era old life 570 – 245 million years ago If all of Earths geologic history is represented by one hour then the Paleozoic era occurred between 9:53 am and 9:56.9 am. The Paleozoic is characterized by the development of diverse sea life and the emergence of the first land plants, first insects, first amphibians, and first retiles. The end of the Paleozoic is marked by a mass extinction of life on Earth. Rocks formed during the Paleozoic are located in a SW-NE trending belt in central North Carolina, and are characterized by intrusive and extrusive volcanic rocks, and metamorphosed sedimentary deposits.
The Paleozoic Era old life 570 – 245 million years ago Age (millions ) PeriodOrganism PermianReptile diversity explodes PennsylvanianLarge scale coal formation in swamps MississippianLand plant diversity explodes, first flying insects, first reptiles DevonianFirst insects (flightless), first amphibians SilurianFirst fish and land plants OrdovicianStarfish and crinoids appear CambrianExplosion of marine life – bivalves, sponges, trilobites, jellyfish, coral Life
The Paleozoic Era old life 570 – 245 million years ago Cambrian: Trilobites & Sponges Ordovician: Crinoids & Starfish Silurian: First fish & land plants Devonian: First amphibians Mississippian: First reptiles Labidosaurus hamatus Ichthyostega
The Paleozoic Era old life 570 – 245 million years ago Rock formed during the Paleozoic is a valuable resource in North Carolina Metamorphic, sedimentary and igneous rocks of Paleozoic age are quarried throughout North Carolina, including the High Point area, for use in a variety of construction projects.
Mesozoic 9:56.9 – 9:58.7 The Mesozoic Era middle life 245 – 70 million years ago
The Mesozoic Era middle life 245 – 70 million years ago The Mesozoic era occurred between 9:56.9 am and 9:57.8 am. During this brief 1.8 seconds, the dinosaurs came and went, and the first birds and mammals emerged. The end of the Mesozoic, like the Paleozoic before it, was marked by a mass extinction. Mesozoic rocks occur principally in southeastern North Carolina, and are characterized by sedimentary deposits of sandstone, shale, and clays.
The Mesozoic Era middle life 245 – 70 million years ago Age (millions) PeriodOrganism CretaceousFirst flowering plants, T-Rex, Triceratops, Dteranodon JurassicDinosaurs grow large: Stegasaurus, Archaeopteryx TriassicReptiles dominate land – crocodiles, turtles and early dinosaurs emerge Life
The Mesozoic Era middle life 245 – 70 million years ago Triassic: early dinosaurs and turtles Jurassic: Archaeopteryx, Stegasaurus and first flowering plant Cretaceous: T-Rex and Triceratops
The Mesozoic Era middle life 245 – 70 million years ago Deposits formed during the Mesozoic are a valuable resource in North Carolina Sand and gravel extraction is the largest income producing mining in North Carolina.
Cenozoic 9:58.7 – 10:00 The Cenozoic Era new life 70 million years ago – present
The Cenozoic Era new life 70 million years ago - present It is only during the last 1.3 seconds that the first human ancestor appeared, ice ages occurred, and modern man evolved. Unconsolidated sands and clays of the Coastal Plain date to the Cenozoic era.
The Cenozoic Era new life 70 million years ago – present Mammals dominate land, human evolution occurs. Climate ameliorates 10,000 years ago, allowing the development of agriculture and human civilization.
The Cenozoic Era new life 70 million years ago – present Deposits formed during the Cenozoic are a valuable resource in North Carolina Aurora, N.C. Phosphate mine. North Carolina is the nations second largest producer of phosphate. North Carolina and Florida account for 95% of the total phosphate produced in the U.S.
Resources General N.C. Department of Environment and Natural Resources United States Geological Survey (USGS) N.C. Geological Survey USGS Studies in N.C. Relief Map of North Carolina Lesson plans/Activities Geosphere links for teachers Resources for K-12 Earth Science Educators USGS resources for secondary schools Mining Institute