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	Geologic time scale - Wikipedia, the free encyclopedia
		The geologic time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth.
		The table of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy, and uses the standard color codes of the United States Geologic Survey.
		Different spans of time on the time scale are usually delimited by major geologic or paleontologic events, such as mass extinctions.
	en.wikipedia.org /wiki/Geologic_time (1763 words)

	Fathoming Geologic Time
		Geologic time is divided into units based on major geological and biological events, such as mountain building phases ('orogeny' in Geo-speak) or mass extinctions (relatively brief periods during which several - sometimes many - lineages die out).
		Many of these blocks of time have strange, exotic-sounding names that are generally derived from the region where they were first clearly differentiated from other such blocks.
		Familiarity with the sequence of the major units of geologic time will greatly enhance your understanding of the evolution of life in general and that of sharks in particular.
	www.elasmo-research.org /education/evolution/geologic_time.htm (1252 words)

	Geologic Time Scale
		The time scale at left is both a reference and a key to the display cases at the museum click on a geologic period to go to that case.
		The two types of geologic time are analogous to the difference between "lunchtime" ("relative time") and the numerical time on a clock, like 12:00pm to 1:00pm ("absolute time").
		This geologic time scale is based upon data from Harland et al., (1990) and Gradstein and Ogg, (1996).
	www.humboldt.edu /~natmus/lifeThroughTime/Timeline/TimeScale.html (419 words)

	Geologic Time
		The immensity of geologic time is very difficult to appreciate from our human perspective, but appreciation is necessary to understand the history of the Earth.
		Geologic time was originally subdivided based on the relative positions of sedimentary rocks.
		The Geologic Column is the chronologic arrangement of rock units from oldest at the bottom to youngest at the top.
	www.geo.ua.edu /intro03/time.html (1599 words)

	Geologic Time Scale - Geological Time Line - Geology.com
		This is because geologic time is divided using significant events in the history of the Earth.
		Eons are the largest intervals of geologic time and are hundreds of millions of years in duration.
		Finer subdivisions of time are possible and the periods of the Cenozoic are frequently subdivided into epochs.
	geology.com /time.htm (409 words)

	Geological Time Scale
		Think of relative time as physical subdivisions of the rock found in the Earth's stratigraphy, and absolute time as the measurements taken upon those to determine the actual time which has expired.
		The overall duration and relative length of these large geologic intervals is unlikely to change much, but the precise numbers may "wiggle" a bit as a result of new data.
		The time scale is depicted in its traditional form with oldest at the bottom and youngest at the top -- the present day is at the zero mark.
	www.talkorigins.org /faqs/timescale.html (669 words)

	A Geologic Time Chart from Rockman
		The study of Geologic Time in relation to the age of the earth is called Geochronology.
		While discrepancies of 2 to 10 million years in determining the age of a rock are not unusual, in terms of geologic time, such discrepancies are relatively minor.
		The most recent Geologic Time is at the top of the chart; the oldest at the bottom.
	www.rocksandminerals.com /geotime/geotime.htm (804 words)

	Palaeos Timescale: Detailed Geological Timescale
		The Geological Time-Scale is hierarchical, consisting of (from smallest to largest units) ages, epochs, periods, eras and eons.
		The Geological time-scale is usually represented as a vertical table to be read from the bottom up; the oldest eras and periods at the bottom, the youngest at the top.
		Geologic Ages of Earth History - Jeff Poling - a detailed and up to date chart showing every era, period, epoch and age of the geological time scale, together with time when began and during in millions of years.
	www.palaeos.com /Timescale/timescale.html (543 words)

	GEOLOGY 112: Geologic Time (Site not responding. Last check: 2007-10-07)
		Geologic time can be referred to as absolute and relative.
		Absolute time is the determination of an absolute age in years before present through the use of radiometric dating techniques.
		Radiometric dates have been assigned to the Geologic Time Scale but the time scale was developed using the appearance and disappearance of fossil assemblages.
	www.odu.edu /webroot/instr/sci/tmmathew.nsf/pages/112time (421 words)

	CVO Menu - The Geologic Time Scale
		An era of geologic time from the beginning of the Tertiary period to the present.
		An era of geologic time between the Paleozoic and the Cenozoic.
		An era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic.
	vulcan.wr.usgs.gov /Glossary/geo_time_scale.html (670 words)

	Geologic Time
		The Geologic Timescale was initially built from many observations of rock sequences from many parts of the world; no single locality contains the entire geologic time sequence, and correlation of geologic units across different localities allowed geologists to construct a composite timescale.
		This was heavily based on sedimentary rocks that contained fossils, which were placed in a relative time sequence based on Darwin's ideas of evolution.
		Geologists immediately started determining the ages of volcanic rock layers that were interbedded with the fossil-containing sedimentary rocks that were used to determine the first geologic timescale, adding absolute ages to the geologic eras and periods.
	www.geology.wisc.edu /homepages/g100s2/public_html/geologic_time.htm (686 words)

	Virtual Silurian Reef -- Geologic Time (Site not responding. Last check: 2007-10-07)
		he relative geologic time scale recognizes intervals of ancient time based on an older to younger sequence of fossil assemblages.
		umbers for millions of years before present are derived from the absolute geologic time scale, which is based on radioactive decay rates of naturally-occurring isotopes of certain elements.
		Calibration of the two time scales is an ongoing and rather involved procedure in geology, and absolute ages assigned to the eras and periods continue to be revised as more isotopic data accumulate.
	www.mpm.edu /reef/geoltime.html (224 words)

	New Page 1
		Geologic time is divided into eons, eras, epochs, and periods.
		An era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic, spanning the time between 544 and 248 million years ago.
		The major divisions, with brief explanations of each, are shown in the following scale of relative geologic time, which is arranged in chronological order with the oldest division at the bottom, the youngest at the top.
	faculty.ucc.edu /egh-damerow/geologic_time.htm (575 words)

	Geological Time (Site not responding. Last check: 2007-10-07)
		The result is the geologic column, which breaks relative geologic time into units of known relative age.
		Thus in the geologic column shown, the absolute ages in the far right-hand column were not known until recently.
		The half-life is the amount of time it takes for one half of the initial amount of the parent, radioactive isotope, to decay to the daughter isotope.
	earthsci.org /teacher/basicgeol/geotim/geotim.html (2255 words)

	USGS Learning Web :: Lesson Plans :: Global Change :: Geologic Age
		The evidence of the pre-existence of ancient mountain ranges lies in the nature of the eroded rock debris, and the evidence of the seas' former presence is, in part, the fossil forms of marine life that accumulated with the bottom sediments.
		Geologists have done the same thing to geologic time by dividing the Earth's history into Eras -- broad spans based on the general character of life that existed during these times, and Periods -- shorter spans based partly on evidence of major disturbances of the Earth's crust.
		The names used to designate the divisions of geologic time are a fascinating mixture of works that mark highlights in the historical development of geologic science over the past 200 years.
	interactive2.usgs.gov /learningweb/teachers/geoage.htm (1084 words)

	Geologic timescale -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-07)
		The geologic timescale is used by (A specialist in geology) geologists and other scientists to describe the timing and relationships between events that have occured during the (A record or narrative description of past events) history of the (The 3rd planet from the sun; the planet on which we live) Earth.
		The (The 3rd planet from the sun; the planet on which we live) Earth is thought by geologists to be about 4570 million years old.
		Intensification of present (Any period of time during which glaciers covered a large part of the earth's surface) ice age.
	www.absoluteastronomy.com /encyclopedia/g/ge/geologic_timescale.htm (2369 words)

	Geologic Time Scale
		A graphic demonstration of the enormous extent of geologic time compared to recent time.
		The time scale is a combination of actual numbers (for the eons and such) and approximate dates from a time scale (for events, such as "early horses"), both from:
		Many events cannot be pinpointed (the geologic record is not perfect or complete), and in any case, most of the "dividing lines" are probably gradual changes, occurring over many thousands or even millions of years.
	www.nthelp.com /eer/HOAtimetp.html (279 words)

	Making The Geologic Time Scale Real
		The concept of imagining 5 billion years of time, the approximate age of the earth, is extremely difficult for students as well as for most teachers.
		I have them divide into 7 or 8 groups and each group is assigned a significant occurrence in earth history, such as the appearance of the first photosynthetic cells The group then consults the geologic time table for that date and converts the time into yards distance on the playing field.
		This provides an excellent time to discuss man's effects upon the earth in that short time of existence, and more especially in the 20th century.
	www.accessexcellence.org /AE/AEPC/WWC/1991/geologic.html (394 words)

	Geologic time 1 (Site not responding. Last check: 2007-10-07)
		Geologic Time, a USGS on-line book by William L. Newman at http://pubs.
		One potential explanation of the geological history of the area is represented in the reconstruction that follows.
		time intervals represent absolute time and were determined after the relative order of the geological time scale was established.
	enterprise.cc.uakron.edu /geology/natscigeo/Lectures/time/gtime1.htm (1597 words)

	Relative Geologic Time (Site not responding. Last check: 2007-10-07)
		Most people's concept of time passage is based on human scale: 100 years is a long time.
		A relative scale timeline will give some idea of the enormous amount of time that had passed from the formation of Earth until the appearance of even the simplest invertebrates.
		Using the Geologic Time Scale chart, divide the timeline into eons and eras.
	www.csun.edu /geology/Class_Notes/ES300L/Geotime/Relative/Relativehtml.html (704 words)

	Geologic Time Scale
		In this geologic column, it is younger on the top than on the bottom, just like the piles of paper on my desk, or a layered sequence of sedimentary rock.
		The Mesozoic was the time that dinosaurs lived, the Paleozoic was before the dinosaurs with fossil plants and sea animals, and the Precambrian is the oldest group of rock: mysterious because so little is known about it.
		Aside from the dinosaurs made famous by the movie of this period, erosion of the highlands was continuing in north Arkansas, and sediments from this time are not exposed at the surface in the state.
	rockhoundingar.com /geology/timescale.html (1469 words)

	Geologic time overview
		The 4.55 billion-year geologic time scale is subdivided into different time periods of varying lengths.
		The time scale on the right shows the subdivisions of geologic time in a form that will fit on a single page.
		To see the entire geologic time scale drawn to scale so you can see the divisions of time in their correct proportions, click here.
	www2.nature.nps.gov /geology/usgsnps/gtime/gtime1.html (572 words)

	Geologic Time
		The Geologic Timetable is a summary of the major events in earth’s history preserved in the fossil record.
		The longest segments of geologic time are called eras.
		Answer the following questions based on the geologic timeline information you were given, as well as the notes we took in class on geologic time.
	www.summitcds.org /parker/geologic_time.htm (864 words)

	Earth Floor: Geologic Time
		It is so old that the world's mountains have been built up and worn down many times, the continents have wandered across the face of Earth like tumbleweeds, and plants and animals have changed many times, from amoebas to dinosaurs to people.
		The age of Earth is so long compared to all periods of time that we humans are familiar with, it has been given a special name: Geologic time.
		The age of Earth is as vast in time as the universe is vast in space.
	www.cotf.edu /ete/modules/msese/earthsysflr/geotime.html (456 words)

	Geologic Time - Part of Kuban's Paleo Place (Site not responding. Last check: 2007-10-07)
		Geologic Time Scale by GSA - Detailed Geologic Time Scale by the Geologic Society of America.
		Geologic Time Scale - This chart is upside down (shows older dates at top, opposite real geologic column), but includes summaries of the dominant life forms in each period.
		Geologic Time Scale - Imagemap derived primarily from the Geologic Time Scale of W.H. Harland, et al.
	paleo.cc /kpaleo/paletime.htm (314 words)

	Practice questions: Geologic Time
		Half the time required for an atom of a given radioisotope to decay.
		Half the time required for all the atoms of a given radioisotope to decay.
		The time required for half of the nuclear material to leave an atom.
	www.usd.edu /esci/exams/geoltime.html (549 words)

	AllRefer.com - period, in geologic time (Geology And Oceanography) - Encyclopedia
		period, unit of time on the geologic timescale.
		Periods are of variable length, generally lasting tens of millions of years, with characteristic fossils found preserved in the sediments deposited during the period.
		It is also used to designate a characteristic of geologic time, such as the glacial period.
	reference.allrefer.com /encyclopedia/P/period3.html (186 words)

	Geologic Time
		Students will be able to compare and relate the span of Earth history to events of historical time and of the human lifetime.
		The idea that a time scale will be analogous to a map scale should help to "set" the lesson and provide some advance organization.
		After a list of events and their scale distances have been formulated, construct the geologic time scale on 5 meters of adding machine paper, beginning with formation of the Earth.
	www.beloit.edu /~SEPM/Time_and_Design/geologic_time.html (291 words)

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