Geologic Profiles The Earth can tells us its history if we only look at the clues Types of rocks present Ages Formations present Sills Dikes Faults

Igneous Intrusive rocks Form as magma solidifies underground Batholith Dike Sill Pipe or Neck Laccolith or Lopolith Phacolith: anticline or syncline

a sill is a tabular pluton that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. the sill does not cut across preexisting rocks, in contrast to dikes, which do cut across older rocks. http://en.wikipedia.org/wiki/Sill_(geology)

Dikes A dike or dyke in geology is a type of referring to any geologic body that cuts discordantly across be either intrusive or sedimentary in origin. http://en.wikipedia.org/wiki/Dike_(geology)

Volcanic Necks Volcanic neck Igneous intrusion How did Devil’s tower form? http://www.unmuseum.org/devtowergeo.htm http://en.wikipedia.org/wiki/Devils_Tower_National_Monument

Batholith is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock-types, such as granite, quartz monzonite, or diorite (see also granite dome). http://en.wikipedia.org/wiki/Batholith

http://en.wikipedia.org/wiki/Syncline

Determining Age Two Methods 1. Relative Age 2. Absolute Age http://en.wikipedia.org/wiki/Fossil

Relative Age: How old is a rock in comparison to others Examine geologic profiles Examine fossils present in the rock Index fossil: a fossil of a plant or animal that was very common during a specific time period (Who’s on First Activity) Law of Superposition _________________ A B A A B A A B A A C A A B B A B

Absolute Age: determining approximate age of rock Radioactive Dating: can be used on igneous rocks and certain fossils radioactive isotopes are present when rocks are made and living things die Radioactive isotopes decay over time and we can measure the amount left to determine age Short clip on C14 http://videos.howstuffworks.com/hsw/22270-the-earliest-immigrants-carbon-14-dating-video.htm

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