The Deep Oceans

Take-Away Points The earth has two kinds of crust Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust How we probe the sea floor Features on the sea floor and edges of continents are products of plate tectonics Submarine landslides are important on continental margins Deep ocean sediment comes from the continents and marine organisms

1. The earth has two kinds of crust The Two-Story Planet 1. The earth has two kinds of crust

Earth Has Two Kinds of Crust 2. Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust

Continental and Oceanic Crust Continental Crust (Granitic) Residue of Long-Continued Partial Melting Thick and Light Ancient: > 2.5 b.y. Oceanic Crust (Basaltic) Derived Directly From Mantle Thin and Dense Young: < 200 m.y. 2. Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust

Investigating the Sea Floor Coring Deep-Sea Drilling Sonar Seismic Refraction Gravity Surveys Magnetic Surveys 3. How we probe the sea floor

3. How we probe the sea floor Piston Coring 3. How we probe the sea floor

3. How we probe the sea floor Deep Ocean Drilling Project Mohole Original Intent: Drill to Earth’s Mantle Drill in Oceans where Crust is Thinnest Hidden Agenda: Complete History of Oceans Challenge: Replacing Drill Bits in 5 km of Water Plate Tectonics Showed that Mantle is Exposed in a Number of Places 3. How we probe the sea floor

3. How we probe the sea floor Deep Ocean Drilling Original Objective Abandoned Renamed Deep Sea Drilling Program Now Called Ocean Drilling Program 3. How we probe the sea floor

3. How we probe the sea floor Sonar 3. How we probe the sea floor

3. How we probe the sea floor Seismic Refraction 3. How we probe the sea floor

Makeup of Ocean Crust 4. Features on the sea floor and edges of continents are products of plate tectonics

Anatomy of a Mid-Ocean Ridge

Continental Margins Shelf Slope Rise Active: Subduction Zones. Sometimes Called Leading Edge Passive: No Subduction. Sometimes Called Rifted or Trailing Edge 4. Features on the sea floor and edges of continents are products of plate tectonics

A Continental Margin 4. Features on the sea floor and edges of continents are products of plate tectonics

Evolution of a Passive Margin 4. Features on the sea floor and edges of continents are products of plate tectonics

Anatomy of a Passive Margin 4. Features on the sea floor and edges of continents are products of plate tectonics

Features of the Deep Ocean Mid-Ocean Ridges Abyssal Plains Fracture Zones Oceanic Trenches Seamounts Submarine Canyons Submarine Fans 4. Features on the sea floor and edges of continents are products of plate tectonics

Crest of the Mid-Atlantic Ridge 4. Features on the sea floor and edges of continents are products of plate tectonics

Sea-Floor Spreading, Mid-Atlantic Ridge Features on the sea floor and edges of continents are products of plate tectonics

Turbidity Flows – Grand Banks, 1929 5. Submarine landslides are important on continental margins

Where Sediment Comes From 6. Deep ocean sediment comes from the continents and marine organisms

Atlantic Sediments

6. Deep ocean sediment comes from the continents and marine organisms Deep Ocean Sediments 6. Deep ocean sediment comes from the continents and marine organisms

Take-Away Points The earth has two kinds of crust Continents have thick, light, granitic crust, Oceans have thin, dense, basaltic crust How we probe the sea floor Features on the sea floor and edges of continents are products of plate tectonics Submarine landslides are important on continental margins Deep ocean sediment comes from the continents and marine organisms