Download Seafloor Spreading

Do Now
Silently & Independently answer the questions
on the chart on your desk.
1. What is continental drift?
2. Why didn’t people believe continental drift at
first?
3. How do you think continental drift and the
layers of the earth work together?
Seafloor Spreading
February 17, 2016
Goal
Use what we know about the layers of the
earth and continental drift to help Wegener
prove his theory.
Reminder: the problem with Wegener’s theory
was that he could not explain how the
continents move. Today, we will explain one way
the continents move!
What do we already know about the
structure of the earth?
Continental
Crust
Oceanic Crust
Review: The crust is the outer most
layer of the earth.
There are 2 types of crust:
• Oceanic Crust: crust that makes up
the ocean floor
• Continental Crust: crust that makes
up continents
Mountains Under the Ocean!
• Mid Ocean Ridges: a mountain that is
on the ocean floor. Formed from cooling
magma
https://www.youtube.com/watch?v=sgDM6m0lUGY
There are cracks in Mid-Ocean Ridges
• Rift: Deep cracks in the middle of mid-ocean
ridges. Magma pours out of rifts.
• Rift Valley: a valley that forms in a mid-ocean
ridge due to hardened magma
There are canyons under water!
• Deep Ocean Trenches: a canyon under water
where ocean floor sinks and melts back into
the mantle
• Subduction: where old oceanic crust is forced
back down into an ocean trench
https://www.youtube.com/watch?v=v7rHMy52WKQ
Seafloor Spreading is the process that
creates this all!
• Seafloor Spreading: the process that forms new
seafloor by adding crust to the ocean floor.
Seafloor Spreading Process:
1. Begins at the mid ocean ridge
2. Magma from the mantle hardens along the mid
ocean ridge, forming a strip of rock
3. As new crust forms in the middle, it pushes the
older crust to the outside of the trench.
4. As the plates move, the older crust goes back
into the mantle
Seafloor Spreading Animations
http://emvc.geol.ucsb.edu/forteachers/flashmovies/Spreading.s
wf
https://www.youtube.com/watch?v=f-nIb8JkFrg
https://www.youtube.com/watch?v=ryrXAGY1dmE
Go back to your Do Now
Go back to your Do Now and fill in the “after”
column.
Fill it in with the correct answers based on what
you learned today.
If your answer was already detailed, then
rewrite it in the “after” column