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Dating Fossils and Methods Used
Transcript of Dating Fossils and Methods Used
Geologists use a chronology known as the geological timescale. It is divided into sections of time called periods. The geological periods is measured in millions of years, EX. 30 Ma means that the rock was formed 30 million years ago. The five main ways fossils can be formed are Freezing (refrigeration), Asphalt, Amber, Carbonization (distilation), and Permineralization. There are two main methods of dating fossils one method is called Relative Dating This video is about the law of superposition Dating Fossils and Methods Used Relative Dating - useful to determine the period in which the fossil or object was from, also to determine if one fossil is older or younger than another
- cannot determine actual age in years of fossil The main concept that is used for relative dating is the law of superposition.
The law was created by Nicholas Steno a Danish scientist.
The law of superposition simply states that each layer in a sequence of sedimentary rocks is younger than the layer below it and older than the layer above it. Main Methods of Dating Fossils Radiocarbon Dating
Dating fossils using Carbon-14 QUIZ
TIME! Work Cited Second Method Used to Date Fossils The second method used to date fossils is the Absolute Dating method which is used to get an absolute date in years
The main method in Absolute dating is radioactive decay which is:
A process where an isotope of an element spontaneously loses particles from its nucleus to create a daughter isotope
Occurs at a specific rate
Uses half-life to compare parent isotopes to daughter isotopes to determine the age of the fossil or rock
2 main elements used are Uranium-235s half-life of 704 million years to determine rocks and fossils. Second element is Carbon-14s half-life of 5,730 years. What is Radiocarbon Dating?
Radiocarbon dating is the method of estimating the age of fossils, rocks or artifact
Some of the types of materials that radiocarbon dating can determine the age of are
The age of an object can also be determined from carbonate deposits such as calcite, dissolved carbon dioxide and carbonates in oceans, lakes or groundwater sources. How is carbon-14 produced?
Cosmic rays enter the earth's atmosphere
The cosmic rays collide with nitrogen-14 (7prt. and 7neu.) which creates carbon-14(6 prt. and 8 neu.) and a hydrogen atom Carbon-14 dating is used to determine the age of an artifact that is up to 40,000 years old.
All living organisms absorb carbon by eating and breathing
After the organism is fossilized and found scientists can determine the age by:
burning a small piece to convert into carbon dioxide gas
radiation counters are used to detect any of the elections given off by decaying carbon-14 as it turns back into nitrogen
by measuring the ratio of carbon-12 to carbon-14 and comparing it to the ratio of a living organism, the age of the object can be determined in years Freezing (refrigeration)-This is the best means of preserving ancient artifacts. Preservation of artifacts is very rare. Various things must happen. The animal must be fully frozen from the time of death until discovery. Asphalt- pits in the ground filled with sticky asphalt or tar. The tar pits were formed by crude oil seeping through fissures in the earth. The lighter elements of the oil evaporate leaving thick sticky asphalt. An example is downtown Los Angeles, there lies a 23 acre park called The La Brea Tar Pits. Permineralization-This is the most common method of fossil preservation. Minerals fill the cellular spaces and crystallize. Amber- most commonly where Insects, spiders, and even small lizard have been found. A insect lands on a tree branch in an area that is now the Baltic sea. While looking for nurtients, the bug steps in sticky sap that the tree has made to protect itself (fugus mostly), the insect struggles to escape, time passes it becomes more and more entombed in the sap until it gets fully covered. How Fossils are Formed?
(Continuation) Carbonization (distillation)- this process of fossilization is most know for preservation of plant leaves, and some soft body parts of fish, and reptiles. It decomposes leaving behind only the carbon. This carbon creates an exact impression in the rock, sometimes with great detail. Information
http://www.youtube.com/watch?v=J2GNJ6tfbY0(How Fossils are Dated)
http://www.youtube.com/watch?v=SEDfRy6DQns(How fossils are made)