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| Activity 3._ The Geological Time Scale |
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The Age of the Earth
Earth is billions of years old and has had a long history of development and change. Most scientists agree now that the Earth is about 4.6 billion year old. How much is a billion? Even ONE BILLION year is difficult for most humans to imagine! When time spans such incredibly large numbers, it is called Deep time. As you read the following, answer the questions on this worksheet.
1. How has Earth changed?
Earth has changed in many ways, but maybe the most amazing change is the moving and drifting of its crustal plates. View this animation of changes that scientist think happened over that past 730 million years.
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2. How much is a billion?
How long do you think it would take you to count to 1 billion? Read about geologic time and find the answer to that question here.
3. How is geologic time counted?
Here is a table showing how the 4.6 billion years of Earth's history are divided up.
Click to view full chart4. Some Latin roots
Learn these latin word and the strange names of geologic time will make more sense to you.
zoic refers to animal life(Source: http://www.mc.maricopa.edu/dept/d43/glg/Study_Aids/geotime.html
paleo means ancient
meso means middle
ceno means recent
5. Different views of deep time
Here are different ways to show the same information. Each shows the time periods of geologic time.
Which one is most interesting to you? Which one is best to help you memorize?
Los Angeles Natural History Museum Geologic Time White Mountain Research Station Time Chart Kansas State University Geology Dept. Time line
6. Learn about each time period
Go to the UCMP Web Geological Time machine. Click and learn about each time period.
7. Fossils
Fossils are the recognizable remains, such as bones, shells, or leaves, or other evidence, such as tracks, burrows, or impressions, of past life on Earth. Scientists who study fossils are called paleontologists. Remember that paleo means ancient; so a paleontologist studies ancient forms of life. Fossils are fundamental to the geologic time scale. The names of most of the eons and eras end in zoic, because these time intervals are often recognized on the basis of animal life. Rocks formed during the Proterozoic Eon may have fossils of relative simple organisms, such as bacteria, algae, and wormlike animals. Rocks formed during the Phanerozoic Eon may have fossils of complex animals and plants such as dinosaurs, mammals, and trees.
(Source: http://pubs.usgs.gov/gip/fossils/scale.html)
Three concepts are important in the study and use of fossils: (1) Fossils represent the remains of
once-living organisms. (2) Most fossils are the remains of extinct organisms; that is, they belong
to species that are no longer living anywhere on Earth. (3) The kinds of fossils found in rocks of
different ages differ because life on Earth has changed through time.
If we begin at the present and examine older and older layers of rock, we will come to a level where
no fossils of humans are present. If we continue backwards in time, we will successively come to levels
where no fossils of flowering plants are present, no birds, no mammals, no reptiles, no four-footed vertebrates, no land plants, no fishes, no shells, and no animals. The three concepts are summarized
in the general principle called the Law of Fossil Succession: The kinds of animals and plants found as
fossils change through time. When we find the same kinds of fossils in rocks from different places,
we know that the rocks are the same age.
(Source: http://pubs.usgs.gov/gip/fossils/succession.html)
8. Earth changed over millions of years - looking back
Read the information on this web site: Putting Time into Proportion. Study this part of the time line. Click on each time period to see what the Earth looked like.
| Copyright © 1999 Gallaudet University
Laurent Clerc National Deaf Education Center All Rights Reserved Mon Jan 6 05:23:32 2003 |
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