1. Continental Margins

2. Most People’s Impression  Ocean is a big, bathtub-like basin.  Shallowest on edges, deepest in middle.  Not at all true!

3. Starting from the Edges  Edges of oceans are called Continental Margins.  Two types: Active and Passive  Active on plate boundary, Passive not.

4. Passive Margins  Most of the world’s continental margins  Nearly all of the Atlantic, Indian, Arctic and Southern Oceans boundaries

5. Characteristics  Three parts:  Continental Shelf  Continental Slope  Continental Rise

6. Continenta l

7. Continental Shelf  Biologically richest part of ocean  Part of the continental crust that just happens to be underwater  Up to 470 miles wide  Usually gets steeper at about 400 feet deep

8. Submarine Canyons  Continental Shelf is cut by many canyons.  Carved by rivers during lower sea levels (Ice Age).  Got even bigger when submerged (more erosion).  Great mix of sea life.

11. Continental Slope  Land abruptly drops downward to meet the continental rise  Can go from 400 feet deep to 10,000 feet in just a few miles  Incredibly varied life depending on the depth

13. Continental Rise  Sediment at the base of the continental slope accumulates to form a less-steep slope called the continental rise.  More erosion, the bigger the rise.  Rise on East Coast formed from the erosion of the Appalachians.  Makes some interesting geology.

14. Active Margins  Surround the Pacific Ocean  Western North and South America  Eastern Asia

15. Active Margins

16. Characteristics: Active Margin  Frequent volcanic and earthquake activity  Narrow or missing continental shelf  Steep continental slope  No continental rise  Deep trenches, possibly filled in with sediments

17. Active Margins

18. Subduction Zone

19.  Ocean Trench – an area where one part of the seafloor Subducts (goes under) another. (Pacific)  Island Arcs – volcanic island chains near Deep- Sea Trenches. (i.e. Philippines)  Marianas Trench is deeper than Mt. Everest is tall by over 2,000 meters. More than 5 times as deep as the Grand Canyon.

20. Chapter 4 Review   On page 127 choose 5 Vocabulary words to define & 5 Thinking Critically questions to answer.