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Absolute Age Radioactive DatingRelative Age Index Fossil

1. _______________________ organism that lived for only a short time which can be used to tell the age of the rock layer it exists in

2. _______________________ a technique used by scientists to determine the absolute age of objects

3. _____________________________ the age of an object or event described in comparison to other objects or events

4. _________________________ Example: The Earth is younger than the Sun

5. _______________________ Test used by scientists to find the exact age of rocks and fossils

6. _______________________ Found in rock layers and allow scientists to determine the relative age of the rocks

Key Idea Scientists can find of relative age of rock

layers based on their order in the earth.

Rock Layers Sedimentary rocks are formed when

sediments are cemented together by heat and pressure to form rocks

This conversion of sediments into rock happens after the sediments are buried by new sediments. Sedimentary rocks form in horizontal layers.

Rock Layers

Horizontal/Vertical Review

Verti

cal

Horizontal

Rock Layers When the sedimentary rock buried deep

enough they undergo more heat and pressure to become different kinds of rock.

Quick Review: if sedimentary rocks undergo heat and pressure to become a new type of rock, what type of rock is it now??

Rock Layers These layers can be used to help

scientists to date rocks and fossils.

Law of SuperpositionThe Law of Superposition states that each undisturbed layer of sedimentary rock is older than a layer above it.

Law of Superposition The bottom layer of rock forms first, which

means that it is the oldest

Each layer above that is younger than the one below and the top layer is the youngest of all.

This ordering is a type of relative dating because you can’t be sure when each layer was formed, so you know the layer’s age in relation to the other layers

Unconformities An undisturbed rock layer means the

horizontal rock layer is intact, it has no disruptions.

Bent

FAULT

FOLDING

IGNEOUS INTRUSION

Igneous Intrusion Here molten rock forces its way up through

sedimentary layers. Because the sedimentary rock have to be present before the molten rock can cut through, the igneous rock must be younger than the layers it cuts through.

The molten rock can erupt and flow to the surface of the earth and form its own layer of igneous rock on top of the sedimentary rock

Unconformity If there is an unconformity, then the

youngest layer may not be on top. Scientists can determine the original order by comparing the disturbed rock layers with a similar stack of undisturbed rock layers.

Geologic Column

Gallery Walk! 2 minutes at each station

Write down the order of age of each layer of the geologic column from OLDEST to YOUNGEST

Unconformities When a rock layer is disturbed, it is

called an unconformity

Exit Ticket1. Which statement is true?A. The oldest layers of rock and soil are closest to the surface of the earth.B. The youngest layers of rock and soil are farther away from the surface of the earth.C. Carbon-14 dating is an example of relative dating, and the law of superposition is an example of absolute dating.D. Absolute geologic dating and relative geologic dating are two methods used by scientists to determine the age of geologic evidence.

2. Which is a process that allows scientists to compare rock layers with others in a sequence to determine their age?A. radiometric datingB. absolute datingC. relative dating