HS - ESS1.C (A) - Earth's Formation - FINAL (RC 4/1/2014)

Module: Earth’s Formation

DCI: ESS1.C (A) Continental rocks, which can be older than 4 billion years, are generally much older than the rocks of the ocean floor, which are less than 200 million years old.

PE: HS-ESS1-5 Evaluate evidence of the past and current movements of continental and oceanic crust and the theory of plate tectonics to explain the ages of crustal rocks.

[Clarification Statement: Emphasis is on the ability of plate tectonics to explain the ages of crustal rocks. Examples include evidence of the ages oceanic crust increasing with distance from mid-ocean ridges (a result of plate spreading) and the ages of North American continental crust increasing with distance away from a central ancient core (a result of past plate interactions).]

The ideas are: 

- continental rocks are older than the rocks of the ocean floor

- continental rocks can be older than 4 billion years

- ocean floor rocks are less than 200 million years old

The big picture here is that we are using the age discrepancy of the two types of rocks to support the idea that the tectonic plates are moving away from each other at the ocean floor. 

Possible Question Starters: 

A diagram of the Mid-Atlantic Ridge is provided. 

Which piece of evidence, collected from the rocks surrounding the Mid-Atlantic Ridge, would support the idea that tectonic plates are moving away from each other? 

correct answer - rocks further away from the ridge are older than those that are closer