1. Sea Floor Spreading Inside Earth Ch. 1.4
Sea Floor Spreading Song =

2. Introduction A. Deep in the ocean the temp is near _freezing_(0C)
B. Many things live in the deep ocean.
1. Giant __tubeworms_ and clams
2. Provide evidence for Wegener’s hypothesis of __Continental Drift__.
500 × 340 - nsf.gov
Brain Pop = Ocean Floor

3. I. Mid Ocean Ridges
A. Sonar = device that bounces sound waves off underwater objects and records them 
B. Mid-ocean ridges are _mountain chains underwater and the island of Iceland.
C. Mapping the ridges makes scientists want to know more about them.

4. 1181 × 1181 - marinesciencetoday.com

5. II. What is Sea Floor Spreading
A. _Harry Hess_ an American geologist studied mid- ocean ridges.
B. His idea was of sea-floor spreading that continually adds new __material___ to the __ocean floor.
Sea Floor Spreading (Nye clip) =

6. Sea Floor
C. Sea floor spreads apart along both sides of mid-ocean ridge as __new crust is added.
D. As the ocean floor moves, the _continents_ move too.
E. _Older_ rock gets pushed further out from the ridge.

7. Sea Floor

8. III. Evidence from Sea Floor Spreading
A. Molten Material
1. A submarine, Alvin went to the ocean floor to find evidence of sea-__floor__ _spreading__. Molten material is erupting from the mantle and hardens quickly when it hits the cold ocean water.
Brain Pop = Submarine

9. Evidence B. Magnetic stripes
1. Scientists found that the rock makes up the ocean floor lies in patterns of _magnetized__ “stripes”.
2.These stripes hold a record of __reversal___ in Earth’s magnetic field.
Magnetic Field Reversal =

10. Evidence C. Drilling samples
1. Drilling into oceanic rock has given us the _ages_ of the rock.
2. Scientists determined that the _youngest__ rocks were __closest__ to the center of the mid-ocean ridges and the older rocks were farther away from the ridges.

11. IV. Subduction at the Trenches
A. deep ocean trenches = underwater canyon
B. Subduction = ocean floor moves back into the mantle through deep ocean trenches

12. Subduction C. Subduction and Earth’s oceans
1. Pacific Ocean is __Shrinking__;
2. Atlantic Ocean is _Expanding___.