Strata, Fossils, & Dating Methods

Objective: •1. Define strata as layers of rock. Understand that lower layers are older and top layers are younger.•2. Define absolute dating as determining the age of a specific rock or fossil. Rock age can be determined by radiometric dating. •3. Define relative dating as determining the order of geologic events. The age of different strata or fossils can be described as “older” or “younger” than others.•4. When given a scenario of strata and fossils, be able to determine the relative ages. When given a chart of radiometric dating methods, be able to determine absolute age.

•The shape of the Earth’s surface is always changing.•Mountains form and erode. Sediment moves from place to place. •Tectonic plates move and volcanoes erupts.

New rock is laid down on the Earth’s surface in horizontal layers.

Each new layer of rock is laid down on top of the previous rock.

Horizontal layers of rock are called strata.

•Upper layers are younger. •Lower layers are older.

Sometimes the horizontal layers are shifted up or down by geologic events.

Movement in the surface of the Earth can cause layers to get tilted vertically.

There are two ways to measure the age of a material (rock or fossil).

Radiometric dating can be used to take the absolute age of the material. The absolute age is the measured age of the specific material in question. For example, is the material 10,000 years old or 10,000,000 years old? OR

The relative age can be taken. The relative age is the age of the material in relation to the surrounding materials. For example, is the material older or younger than the surrounding material?

This information can help us determine when different organisms lived and when they went extinct.

A

B

C

Practice:1) Which stratum is

youngest ?2) Which stratum is

oldest?3) Which strata formed

beneath a body of water?

4) Which strata formed during a dry period?

5) a. Which stratum formed during a challenging time for life?b. What could possibly be to blame for the lack of fossils in this layer?

DE

F

Practice Continued:6) Which organisms still exist today?7) Which organism has been extinct the longest?8) Which two known fossils can help us determine

the relative age of the unknown fossil?

A B C D E F G H I

Today’s Dig

Quiz-Quiz-Trade•Between four students, quarter one sheet of paper. Write your student number and period at the top of your piece. •Create two of your own questions about the diagram for a classmate to answer.