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Relative vs Absolute Age Dating
Transcript of Relative vs Absolute Age Dating
The Relative Age is the age of a rock or fossil described in comparison to that of another rock or fossil. It is not the
age, instead it is an educated guess as to the approximate age based of the things found around the fossils or rocks.
How Relative Age is Determined
There are several methods used to find the relative age of a fossil
Law of Superposition- describes that in undisturbed sedimentary rock layers, older rock layers lie under younger rock layers.
Intrusions- an intrusion is an igneous rock that has "crept" though the sedimentary rock layers. It is important to remember the difference between the two different kinds of rock.
Index Fossil- fossil of an organism that existed for only a short period of geologic time and lived in many place. They can provide fairly precise information about the age of a rock layer.
The actual age, in years, of a rock or fossil. In other words, how old the fossil is (how long ago it was made).
How Absolute Age is Determined
There are several methods scientists use to determine the actual age, absolute age of rocks and fossils
Radioactive Dating- this method measures the age of a material by comparing the amount of a radioactive substance with the amount of its decay product.
Radioactive Decay- as unstable (radioactive) atoms get older, they loose energy. This process is measurable; certain atoms loose this energy at a set rate (like having the cruise control on in a car to keep it at a certain speed).
Carbon-14 - this particular atom is used to date organic material 50,000 years old or less.
Uranium- as this element looses energy, it decays into lead. This takes billions of years making it ideal for finding the age of rocks.
Half-Life- as radioactive elements decay (lose their energy) they turn into other elements. The half-life is the amount of time it takes for half of those elements to turn into another element (known as the parent element).
What is all means
There are many methods for determining the age of rocks, fossils, and organisms. Geologists use these methods to help them to understand Earth's History. The theory of
Uniformitarianism (states that the Earth is always changing)
makes it important to understand our past as it will give us clues to the future.
Relative vs. Absolute Age Dating
How scientists determine the age of fossils, rocks, and other geological artifacts.
Draw a Venn Diagram and compare and contrast relative and absolute age dating
Relative Age Dating
Absolute Age Dating
Cast vs Mold
There are several ways in which fossils are created:
Mold- forms when sediments bury an organism and the sediments change into rock; the organism decays leaving a cavity in the shape of the organism
Cast- forms when a mold is filled with sand or mud that hardens into the shape of the organism
Petrified (permineralized)- forms when minerals soak into the buried remains, and changing them into rock.
Preserved- forms when entire organisms or parts of organisms are prevented from decaying by being trapped in rock, ice, tar, or amber
Carbonized- forms when organisms or their parts are pressed between layers of soft mud or clay that hardens squeezing almost all the decaying organism away leaving the carbon imprint in the rock
Trace- forms when the mud or sand hardens to stone where a footprint, trail, or burrow of an organism was left behind