Methods of Geological Dating: Numerical and Relative Dating - Video & Lesson Transcript | Methods of Geological Dating: Numerical and Relative Dating - Video & Lesson Transcript |

Describe relative dating techniques using fossil sequence in strata, the grand canyon and relative dating

The brachiopod, crinoid, eurypterid, foraminifera, gastropod, horn coral, pelecypod, and trilobite could probably not be used as index fossils since they overlap more than one stratum.

Geological unconformities All of these processes confuse the stratigraphic record. The first card in the sequence has "Card 1, Set A" in the lower left-hand corner and represents the bottom of the sequence.

Relative Dating

It is based on the principle of superpositionwhich is that if there are layers of deposits, those laid down first will be on the bottom and those laid down last will be on the top. As a result, the amount of fluorine and other trace elements progressively increase.

At the same time, percolating ground water deposits trace amounts of fluorine and other elements, such as uranium, into the bone. This was verified through the use of X-ray fluorescence examination. Mold What is an object created when sediment fills a mond and becomes a rock.

In sedimentary rock What animals are commonly preserved in rock? Dinosaurs What trait probably helped mammals survive? So, how do we know how old a fossil is?

Find a rock layer that has at least one of the fossils you found in the oldest rock layer.


Because of shells What animals are well preserved in amber? Index fossils are fossils that are known to only occur within a very specific age range. After reexamining the strata at the Piltdown site, the evidence of a hoax was published in Relative Dating What do scientists know about an undisturbed sequence of rock layers?

Fluorine Analysis When bones, teeth, or antlers are found at a site, fluorine analysis can be used to tell us whether or not the animals they were from actually lived at about the same time.

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If not, then at least one of them must be physically out of context. Marine sedimentary rocks such as limestone, shale, and sandstone might contain fossils similar to those depicted in this activity.


Since this card has a common letter with the first card, it must go on top of the "TC" card. On a larger scale, even between continents, fossil evidence can help in correlating rock layers. For instance, if we find a fossil bone below the strata 3 rock level shown in the illustration above, we assume that the animal most likely lived at a time before that layer was formed.

It is not uncommon to have students reverse the M and D for example and begin the sequence with DM because that is the way they are printed on the card.

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Most organisms never become fossils What does the fossil record NOT reveal? Scientific measurements such as radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age.

The cards should be duplicated, laminated, and cut into sets and randomly mixed when given to the students. Unfortunately, by Charles Dawson and all of the other people involved with the Piltdown Man discovery and analysis had died, so we do not know for sure who was responsible for the hoax.

This uses radioactive minerals that occur in rocks and fossils almost like a geological clock. Isotopes When is an isotope stable?

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Reptiles were the dominant species When did the Cenozoic era begin? Stratigraphic Section for Set B. Folding What is molten rock that has squeezed into existing rock and hardened?

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Era What is the third largest division of geologic time? As a result, it was difficult to chronologically compare fossils from different parts of the world.

Cast Why is the fossil record incomplete? The sequence must be exactly in the order as written.

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This principle is logical and straightforward. Scientists also use direct evidence from observations of the rock layers themselves to help determine the relative age of rock layers. When it has the same number of protons and electrons What happens during radioactive decay?

Once an organism disappears from the sequence it cannot reappear later.