1. Subduction, Seafloor Spreading, and Ring of Fire:

2. Sea-Floor Spreading Objectives: 1.What is the process of Sea- floor Spreading? 2.What happens to the ocean floor at deep ocean trenches?

3. Vocabulary: 1.Mid-ocean Ridge – Longest chain of mountains extending into all of Earth’s oceans, that curves like the seam of a baseball along the sea floor.

4. Mid-Ocean Ridge

5. 2.Sea Floor Spreading – The process that adds new material to the ocean floor at the mid-ocean ridge. Molten material erupts and spreads out through the valley that runs along the center of the Mid-ocean Ridge. It then pushes aside the rock that was already there.

6. 3.Deep Ocean Trench – This forms from Subduction (The Oceanic Crust bends downward forming a deep underwater canyon on the ocean floor).

7. 4.Subduction – When the ocean floor sinks beneath a deep ocean trench and gets swallowed by the mantle.

8. Subduction Diagram

9. Sea-floor Spreading and Subduction can change the size and shape of the oceans. (See Diagram next 2 slides) The Pacific Ocean, aka “The Ring of Fire”, has lots of Subduction Zones, thus it is getting smaller.(See Diagram next 2 slides) The Atlantic Ocean is expanding.

10. Subduction and Seafloor Spreading:

11. Ring of Fire Diagram: