Transcript Section 11.2 Seafloor Spreading

Do now:
Read 4.2
Objectives:
You will learn to explain seafloor
spreading.
You will learn to recognize how
age and magnetic clues support the
theory of seafloor spreading.
- invention of echo-sounding
____________________
devices
allowed the construction of accurate
maps of the ______
ocean floor
- using sound waves, researchers
underwater system of
discovered an ___________
ridges or __________,
mountains and valleys
_______,
continents
like those found on the ____________
Harry Hess proposed this
- Early 1960s: __________
theory
magma from Earth’s
- the idea that _______
mantle rises to the surface at mid_______
ocean ridges and cools to form new
seafloor which new magma slowly
________,
pushes away from the ridge
__________________
____________
- there
were no rocks older than
180 million years, however, some
___________
___________
continental rocks are almost
_________
4 billion years old
- youngest rocks were at
mid-ocean ridges
_________________
- age of rocks became ______
older farther
from the ridges on both sides
- magnetic data is recorded by a
magnetometer
______________
ocean floor showed
- rocks on the ______
magnetic reversals
- the magnetic alignment of the rocks
reverses back and forth in strips
parallel to the mid-ocean ______
ridge
________
LET’S REVIEW!
• The invention of _____________ allowed the
construction of accurate maps of the ocean
floor.
• What are mid-ocean ridges?
• Who discovered the idea of seafloor
spreading?
• What is a trench? When is one formed?
• What two pieces of evidence proved the
theory of seafloor spreading to be correct?
- Read section 4.2 and do
questions #1-5 Due Wednesday
- Notes Packet due Thursday
- Study for 4.2 quiz Thursday