Science in Action 7 pages 415 to 418 or Science Focus 7 pages 418 to 427
There are several methods used to interpret fossils such as absolute dating, relative dating and fossil records. These methods are important because they give us an idea what and where creatures lived on the earth. Also fossils provide information on environmental changes that have occurred in the past. This information is important since history has a tendency to repeat itself. For example in the past glacial ages occurred which would possibly indicate that similar changes might occur in the future.
ABSOLUTE DATING
Absolute dating is a method used to tell how old an item or fossil is in years. The amounts of certain elements in the rock can tell scientist how old something is. The method employed to find something's age is called radiocarbon dating. Over billions of years some elements can change into others. Such as uranium in rock with change into lead after a period of 4.5 billion years. The time for this element to change 50% of its material is called its half life. Different elements will take different amounts of time to undergo these changes. From knowing how long the elements take to decompose into the daughter material and measuring samples, absolute dating can occur.
RELATIVE DATING
Relative dating is a relationship of the age of the fossils to the age of the strata, or layer of rock, that they are found in. For the most part the further you dig down into sedimentary rock the further you go back in time. Therefore the principal of superposition applies. This principal states that in undisturbed layers of rock, the oldest layers will be on the bottom and the youngest layers will be on the top. Using this concept, we can assume that fossils found in layers of lower layers of rock will be older than those found above it.
FOSSIL RECORDS
Index fossils are fossils which where only on the earth of a short and set period of time. From knowing when these organisms lived and died they can be used to determine the age of the material they were found in. By looking at the layers and the fossils found in them, the time can be determined when certain life forms lived on this Earth.
If you have never been to Drumheller's Tyrrell Museum Website, click here
