The Tales Rocks Tell and the Changes to the Story

Principle of Superposition and Unconformities

Mountains BrainPOP has good examples of unconformities

Nicholas Steno (1638-1686)Danish Catholic Bishop and

ScientistStarted in anatomy but fossils

expanded his work into geology

Introduced the concept of the Principle of Superposition, Unconformities and fossils being part of once living organisms.

Scottish FarmerStarted in medicine but

chemistry expanded his work into geology

Introduced the concept of the Rock Cycle (before Hutton it was thought that rocks precipitated out of water)

Introduced the concept of Deep Time (Earth is millions of years old)

Before Hutton the Earth was thought to be about six thousand years old (Oct. 22, 4004 BC)

James Hutton (1726-1797)

In rock layers (strata) the oldest rocks are on the bottom and the newest rock is on the top.

This allows you to find the relative age (older/newer) of the rocks based on their position.

Analogies:The dirty clothes pileMagazines

Principle of Superposition:

Unconformities are changes that occur in the rock layers (strata).

Unconformities can be caused by plate tectonics (earthquakes), volcanic activity (magma pushing and lava flows), erosion (water and glaciers), lack of deposition (no new sediment is deposited over a long period), etc.

Unconformities:

What happened?

B

A

C

D

E F

This is NOT a man made

layer.

Turn to page 196 in your ScienceSaurus.

Angular Unconformity (A re-write)

Disconformities (missing chapters)

The Grand Canyon (AZ)

Under Armour’s “new line”:

“Un-Ken-Formity”Doesn’t it look like someone took Play-Doh and “squished” it up?

Devil’s Bridge - Sedona, AZ