Download Seafloor Spreading (LT 1, 3-5)

Write the following on the Goal Sheet in your
notebook.
October 7 Goal: I can explain the evidence for seafloor
spreading (LT # 4)
Rate your understanding of this topic at this
moment, and how much effort you plan to give
to class today.
Plate Tectonics
Learning Targets
Indicator: Earth’s crust consists of major and minor tectonic plates that move relative to each other. Learning Targets:
I can …
1. Explain how our understanding of plate tectonics has developed through the contributions of Alfred Wegener, Harry Hess, and Robert Dietz
2.
3.
4.
5.
Explain 4 pieces of evidence for the theory of continental drift.
Describe the process of seafloor spreading
Explain at least three pieces of evidence for seafloor spreading
Explain how evidence of polar wandering supports plate tectonics
6. Explain which layer of earth is divided into tectonic plates
7. Tell that the tectonic plates float on the asthenosphere
8. Identify and describe the geothermal movements that cause plate motion.
Vocabulary:
continental drift, seafloor spreading, convection, tectonic plate, Mesosaurus, Glossopteris, Pangaea, mantle, asthenosphere, lithosphere, magnetic field, trench, subduction, rift valley, mid­ocean ridge, polar wandering, geothermal
Di
etz
on Page 7
He
ss
sound waves
at
proposed the theory of seafloor spreading
magma
cools, contracts and begins to sink helping
to form the
obtains rock samples from the seafloor
younger
sink below
reversed itself many times in the past
reverses back and forth over time in strips parallel to the mid­ocean ridges
What did they find from all these core samples?
The youngest rocks are found at the
mid-ocean ridges. As you travel away
from the mid-ocean ridge on either side,
the rocks get progressively older. This
suggests that new rock (crust) is being
formed at the mid-ocean ridge, and is
pushing the seafloor away from the midocean ridge like a conveyer belt.
page 10
mid­ocean ridge
deep sea trench
A/C
B
Ocean floor near the center slit is youngest
rocks age as move towards side slits
the pattern of reversals in Earth's magnetic field that is recorded in rocks as magma cools
hot magma rises (because it is less dense) and pushes on crust causing it to move ­ cooler magma sinks back into mantle (convection current)
mid-ocean ridge
page 11
page 12
the youngest rocks are at the
mid-ocean ridge and get
progressively older as move
away (new rock formed at ridge)
the magnetic field gets recorded
into rocks when lava cools and
the pattern of reversals is the
same on both sides of the ridge.
the ocean floor gets pushed
under continental crust along
with ocean water which gets
trapped in mantle, continental
crust gets folded into mountains
page 12
https://www.e­education.psu.edu/earth520/content/l3_p5.html
Polar wandering is.....
seen by the layers of lava rocks from a
volcano. As you travel deeper into older
rocks, the rock's magnetic north points a
different direction - so either the
magnetic north pole has moved or the
continent has.
S. America
page 13
Rift Valley
(African rift valley)
New Ocean Basin
(Red Sea)
Mature Ocean
(Atlantic)
Mid­Ocean Ridge
Sediments
October 15
October
Question:
Notebooks:Savanna & Meltie
Timekeeper: Jesse
Proposed by Harry Hess in 1960s
seafloor spreads allowing magma to rise Theory of creating new ocean floor at mid­ocean ridges; Continental Drift
old ocean floor destroyed at trenches (subduction)
Theory of
Seafloor Spreading
Evidence: Pillow­shaped rocks found on seafloor
Theory of
can only form when magma cools underwater
Pattern of reversals in magnetic field (recorded in rock) is the same on both sides of mid­ocean ridge
youngest rocks found at mid­ocean ridges; rocks get older as move away from the ridge
Proposed by W. Jason Morgan and Theory of Xavior Le Pichon in 1967
Earth's lithosphere is divided into Continental Drift
plates which move relative to each other; plate movements are caused Theory of
by convection currents in Earth's Seafloor Spreading
asthenosphere; these movements cause earthquakes and volcanoes
Theory of Plate Tectonics