Finding Relative Age

Do Activity 12-D Part II on p. 263

Answer “Discussion” Questions p.

263

The Law of Superposition: -In sedimentary rock, the older layers are found towards the

bottom and younger layers towards the top.

http://www.purchon.com/ecology/images/strata.jpg

Older rock

Younger rock

The Crosscutting Rule -Any event that disturbs a rock is always more recent than the rock itself.The dike is

younger than the strata

Fossils in the form of shells, bones or imprints become encased in sedimentary layers.

Fossils in deeper layers are ____er than those above.

http://www.bbc.co.uk/schools/gcsebitesize/img/bifossils.gif

Fossils in the form of shells, bones or imprints become encased in sedimentary layers.

Fossils in deeper layers are _OLDer than those above.

http://www.bbc.co.uk/schools/gcsebitesize/img/bifossils.gif

Fossils found in the deeper layers of the Grand Canyon are quite unfamiliar! (Living things have changed!) http://dommy.com/alan/pix/grand-canyon.jpg

?

Olenellus (a trilobite) first appeared about 550 million years ago and became extinct about 250 million years ago. Rock with trilobite fossils are between ____ and ____ million years old.http://sun2.science.wayne.edu/~geology/GEO1010/images/home/Trilobite.gif

An index fossil is a fossil that is useful for indicating the geological time when a sediment was deposited.A paleontologist – a scientist who studies ancient life forms.

http://www.msnucleus.org/membership/html/jh/earth/stratigraphy/images/paleontologist.gif

Do Activity 12E on page 266

The Standard Geological Column -an imaginary collection of all the sedimentary rock layers and their fossils from everywhere in the world!http://www.abheritage.ca/abnature/geological/photos/rock_column_thu.jpg

Named after 2 Celtic Tribes

Named after Jura

mountains in Switzerland

Do Review 12.3 on page 269