Sea Floor Spreading
Chapter 4.4
• What is the
mid-ocean
ridge?
• The mid-ocean ridge is the longest
chain of mountains in the world.
• What do we
use to map the
mid-ocean
ridge?
• The mid-ocean ridge is mapped
using Sonar.
• What idea did • Harry Hess proposed that
Harry Hess
ocean floors move like
propose?
conveyer belts, carrying the
continents along with them.
This movement begins at the
mid-ocean ridge called Sea
Floor spreading.
• How does
• At the mid-ocean ridge,
this
molten material rises from
movement
the mantle and erupts.
at the midThe molten material then
ocean ridge
spreads out, pushing older
begin?
rock to both sides of the
ridge.
Three Types of Evidences:
• What types of
evidence
support the
theory of seafloor
spreading?
1. Evidence from Molten Material
• How does
magnetic
stripes support
the theory of
Sea floor
spreading?
2. Evidence from Magnetic Stripes
In Order to understand
Magnetic Stripes lets talk
about the Earth’s magnetic
North!
Presented by Ms. Macris and Ms. Burke
from UCLA
What exactly is the North Pole?
The Earth acts like a giant magnet
because of it’s metallic core!
Sometimes the magnet flips
over!
Magnetic
reversal
video
How the seafloor got it’s stripes!
• Drilling
Samples
•
Evidence of Sea floor
spreading video
3. Evidence from Drilling Samples
Youngest rock was found in the
center and older further away.
• What is
• Subduction is the process
subduction? by which the ocean floor
sinks beneath a deepocean trench and back into
the mantle.
• animation of subduction
• another animation of plate tectonics
Subduction
• What is
created
where
subduction
occurs?
• The ocean floor plunges into
deep underwater canyons
called deep-ocean trenches.
•
Deep Ocean Trench
How does this help explain
Wagner’s idea of continental drift?
• Why doesn’t the
ocean floor keep
getting wider?
• The Pacific Ocean is getting
smaller and the Atlantic Ocean is
getting bigger.
• Bill Nye sea floor spreading
video