Development of a Theory Chapter 6 Lesson 2. Mapping the Ocean Floor Echo Sounder – tool helped...

Development of a Theory

Chapter 6 Lesson 2

Mapping the Ocean Floor

• Echo Sounder – tool helped scientists mapping the depths of the ocean floor.

• Found MOUNTAIN RANGES called Mid-ocean Ridges.

Seafloor Spreading

• This is process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away.

• https://www.youtube.com/watch?v=k-_Z6p5cjKg

• Short video for you guys!! Pretty cool and it has Bill Nye

Seafloor Spreading Continued

• Floor spreads apart at plates, it spews out lava. Creates basalt.

• Pillow lava…• Older basalt away from center. Newer is close

to ridge.• This helped Wegener’s theory (of course he is

frozen in Antarctica, so he has no idea… no we may not go there and dig him up!!!!!)

Pillow Lava.. Cools super quick

Topography of the Seafloor

• Remember that topography means the shape of the land…. And the seafloor!!!!

• Rugged mountains on seafloor can form 2 ways…

• Lava build up creating mountains• Lava cools and cracks, moves and creates the

ranges.

Topography of the Seafloor Cont’d

• Abyssal plains – when the sediment accumulates and creates flat surfaces on the ocean floor.

Supporting Wegener

• So…. If the floor is spreading and crust is getting bigger…. The continents are MOVING when new lava comes out!

• Being PUSHED by new lava!

Normal Polarity

• Compass needle will point North.

• This picture shows theEverything going to the North.

Magnetic Reversal

• When the magnetic field changes direction!

Reversed Polarity

• When the needle points South on a compass.

Rocks show Magnetic Reversal

• Basalt is iron rich.• Iron is magnetic.• It will point in different directions based on

the polarity of the Earth.

Video

• So now that you are completely confused by the magnetic stuff….

• Watch a video.

• https://www.youtube.com/watch?v=BCzCmldiaWQ

Last Video

• https://www.youtube.com/watch?v=ZzvDlP6xd9o