Geologic Time
Linda Kennedy, Department of Geography, UNCG, July 2011
An Introduction
Age (millions)
Era Period
2 Cenozoic Quaternary
66 Tertiary
144 Mesozoic Cretaceous
208 Jurassic
245 Triassic
286 Paleozoic Permian
320 Pennsylvanian
360 Mississippian
408 Devonian
438 Silurian
505 Ordovician
570 Cambrian
4,500 Precambrian
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 Timethere’s just so much of it!
Geologic Timethere’s just so much of it!
History written in stoneEvidence from rocks allows geologists:
To identify the geological processesthat resulted in the formation of each rock.
To reconstruct atmospheric/climaticconditions and changes through time.
To reconstruct plant/and or animal lifeprevalent during the formation of rocks.
http://www.abdn.ac.uk http://news.nationalgeographic.com http://events.ucr.edu
http://dinobase.gly.bris.ac.uk
http://uts.cc.utexas.edu http://nsidc.org
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 Timethere’s just so much of it!
Present
Precambrian9:00 – 9:53
The Precambrian Era4.5 billion – 570 million years ago
Most of the past hour – 53 minutes –is known as the Precambrian era. Earth’s crust formed at approximately 9:01 but much of it has been recycled or altered
from it’s 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 Era4.5 billion – 570 million years ago
The Precambrian Era4.5 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.
http://gsc.nrcan.gc.ca/paleochron/03_e.php
http://gsc.nrcan.gc.ca/paleochron/03_e.php
http://www.eps.mcgill.edu
The Precambrian Era4.5 billion – 570 million years ago
Mount Airy, Surry Co. The world’s 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.
http://ncpedia.org/symbols/rock
Rock formed during the Precambrian is a valuableresource in North Carolina
North Carolina is the nations top producer of mica, amineral used in a variety ofindustries.
Mica
http://www.minfind.com
Paleozoic9:53 – 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 Earth’s 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
)Period Organism
286-245 Permian Reptile diversity explodes
320-286 Pennsylvanian Large scale coal formation in swamps
360-320 Mississippian Land plant diversity explodes, first flying insects, first reptiles
408-360 Devonian First insects (flightless), first amphibians
438-408 Silurian First fish and land plants
505-438 Ordovician Starfish and crinoids appear
570-505 Cambrian Explosion of marine life – bivalves, sponges, trilobites, jellyfish, coral
Life
The Paleozoic Era“old life” 570 – 245 million years ago
Cambrian:Trilobites &Spongeshttp://www.fossilmuseum.net http://www.palaentology.geo.uu.se
Ordovician:Crinoids &Starfishhttp://www.oum.ox.ac.ukhttp://museumvictoria.com.au
Silurian:First fish & land plants http://tolweb.org http://ww.cavehill.uwi.edu
Devonian:First amphibianshttp://www.exploratorium.edu
Mississippian:First reptileshttp://www.bluesci.org
Labidosaurus hamatus
Ichthyostega
The Paleozoic Era“old life” 570 – 245 million years ago
Rock formed during the Paleozoic is a valuableresource in North Carolina
http://www.wakestonecorp.com
Metamorphic, sedimentaryand igneous rocks ofPaleozoic age are quarriedthroughout North Carolina,including the High Point area,for use in a variety ofconstruction projects.
Mesozoic9:56.9 – 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 birdsand 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)
Period Organism
144-66 Cretaceous First flowering plants, T-Rex, Triceratops, Dteranodon
208-144 Jurassic Dinosaurs grow large: Stegasaurus, Archaeopteryx
245-208 Triassic Reptiles 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 andfirst floweringplant
http://www.itsnature.org http://www.askabiologist.org.uk http://news.ufl.edu
Cretaceous: T-Rex and Triceratops
http://news.bbc.co.uk http://www.nmnaturalhistory.org
http://www.impactlab.net http://www.itsnature.org
The Mesozoic Era“middle life” 245 – 70 million years ago
Deposits formed during the Mesozoic are a valuableresource in North Carolina
http://www.boggspaving.com
Sand and gravelextraction is the largest incomeproducing miningin North Carolina.
Cenozoic9:58.7 – 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
http://www.gsi.ie
http://www.dailymail.uk.co
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 valuableresource in North Carolina
Aurora, N.C. Phosphate mine. North Carolina is the nations secondlargest producer of phosphate. NorthCarolina and Florida account for 95% of the total phosphate produced in the U.S.
http://www.wazengineeriing.com
Resources
General
N.C. Department of Environment and Natural Resourceshttp://portal.ncdenr.org
United States Geological Survey (USGS)http://www.usgs.gov
N.C. Geological Surveyhttp://www.geology.enr.state.nc.us
USGS Studies in N.C.http://pubs.usgs.gov/fs/fs-033-96
Relief Map of North Carolinahttp://geology.com/shaded-relief/southeast.shtml
Lesson plans/Activities
Geosphere links for teachershttp://nesen.unl.edu/scienceresources/linksgepsphere.asp
Resources for K-12 Earth Science Educatorshttp://www.geosociety.org/educate/resources.htm
USGS resources for secondary schoolshttp://education.usgs.gov/common/secondary.htm
Mining Institutehttp://www.mii.org