Relative Age of Rocks What is relative age

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Relative Age of Rocks

Relative Age of Rocks

What is relative age? • The relative age of a rock is its age

What is relative age? • The relative age of a rock is its age compared to the ages of other rocks • Absolute age is the number of years since the rock formed – Found using radioactive dating- ratio of radioactive and stable isotopes found in rock • It can be difficult to determine the absolute age of a rock, so we can use relative age.

Relative age assumes that… The lower layers are older than the upper layers. Lower

Relative age assumes that… The lower layers are older than the upper layers. Lower layers would have been deposited first. YOUNGEST OLDEST

Relative age assumes that… An object cannot be older than the materials it is

Relative age assumes that… An object cannot be older than the materials it is made up of. The chocolate chips had to be made BEFORE the cookies.

Igneous Rocks Did they cause metamorphosis in the surrounding rock? YES = igneous rock

Igneous Rocks Did they cause metamorphosis in the surrounding rock? YES = igneous rock is younger than surrounding rocks gcsescience. com

Igneous Rock Did they cross cut preexisting rock? YES = they are younger than

Igneous Rock Did they cross cut preexisting rock? YES = they are younger than the rock they cross cut

Igneous Rock Were sediments deposited on them after they formed? YES = they are

Igneous Rock Were sediments deposited on them after they formed? YES = they are older than the sediments.

Photo by Marli Miller, University of Oregon. Used by permission. About. com(fair use policy)

Photo by Marli Miller, University of Oregon. Used by permission. About. com(fair use policy) Intrusion of diorite, caused limestone above and below to become marble.

Principle of Superposition In sedimentary rocks, the oldest rocks are on the bottom, and

Principle of Superposition In sedimentary rocks, the oldest rocks are on the bottom, and the youngest are on the top. YOUNGEST OLDEST

Principle of original horizontality Sedimentary layers are deposited horizontally. Layers that are not horizontal

Principle of original horizontality Sedimentary layers are deposited horizontally. Layers that are not horizontal have been deformed by movements of the Earth’s crust. teacher 2. smithtown. k 12. ny. us

Principle of faunal succession Fossils of plants and animals occur in a definite order,

Principle of faunal succession Fossils of plants and animals occur in a definite order, a period of geologic time can be determined by its fossils. Index Fossil = fossil of organism that is easily identified, occurred over a large area, and lived during a well-defined period of time. uvm. edu

Principle of crosscutting relations Geologic features, like faults and igneous intrusions, are younger than

Principle of crosscutting relations Geologic features, like faults and igneous intrusions, are younger than the rocks they cut through. earthscienceinmaine. wikispaces. com

Principle of Inclusions Rock that contains inclusions of preexisting rocks is younger than the

Principle of Inclusions Rock that contains inclusions of preexisting rocks is younger than the rocks that the inclusions came from. http: //imnh. isu. edu/exhibits/online/geo_time/geo_principles. htm