May 13, 2014Open up your ISN. Call the next

available left side page #84.Title the page “Vocabulary”.Call the following page #85.

Title the page “The Rock/Fossil Record Goals”

Today’s goal:Explain how scientists determine the relative age

of rock layers.

The Rock RecordChapter 8 section 1

5/13/14ISN 86 – “DIAGRAMS”

ISN 87 – “NOTES”

And no…..we are not talking about this rock

These are the types of rocks I am referring to…

State the principles of uniformitarianism…. What does this

principle tell us?

• Current geologic processes, like erosion, shaping the Earth now, shaped the Earth in the past.

Basically…. The past is the key to the present!

Explain how the law of superposition can be used to determine the relative

age of rocks…

• Relative age of rocks: Indicates that one layer is older or younger than another layer but does not indicate the rock’s age in years.

• Law of superposition: States that an undeformed sedimentary rock layer is older than the layers above it and younger than the layers below it.

Law of superposition-Top layers are youngest

-bottom layers are the oldest

Unconformities: An interruption in the geologic record

There are 3 types of unconformities

1. Nonconformity: When a stratified rock rests upon unstratified rock.

2. Angular unconformity: The boundary between a set of tilted layers and a set of horizontal layers.

3. Disconformity: The boundary between horizontal layers of old sedimentary rock and younger, overlying layers that are deposited on an eroded surface.

Applying the law of crosscutting relationships to determine the relative age of rocks…

• Law of crosscutting relationships: States that a fault or igneous intrusion is always younger than the rock layers it cuts through. The law of crosscutting relationships can be used to determine the relative ages of rock layers and the faults an intrusions within them.