Transcript Plate Tectonics

Plate Tectonics
Earth on the move
Lyell’s breakthrough.
Uniformitarianism
Uniformitarianism (notes)
• Uniformitarianism: The forces active
today are the forces that were active in
the past.
• “ The present is the key to the past” …
concept developed by Charles Lyell
• Leads to the understanding that the Earth
that is many millions of years old.
Alfred Wegener’s Evidence for
Continental Drift (circa 1915 AD)
• The same Fossils of animals
and plants in distant continents.
• Ancient mountains, glaciers
and coal deposits become
continuous once continents
are put back together again
• Identical sedimentary rocks
found in identical layers at
remote regions of the world
• Look on page 21 of text.
Alfred Wegener’s Theory
of Continental Drift
• Makes a theory for
the continents once
having been together
in a super-continent
called PANGAEA
• BUT, he has no
mechanism or
explanation for what
could move the
massive continents.
−60 °C (−76 °F)
•
Six months later, on May 12, 1931,
Wegener's body was found halfway
between Eismitte and West camp. It
had been buried (by Villumsen) with
great care and a pair of skis marked
the grave site. Wegener had been fifty
years of age and a heavy smoker and
it was believed that he had died of
heart failure brought on by
overexertion. His body was reburied in
the same spot by the team that found
him and the grave was marked with a
large cross.,
• Published in
1915
What is this?
How do we know it existed
Mid Atlantic Ridge
From Space
Paleomagnetism
Paleomagnetic info from the sea floor
(page 27)
Plate Boundaries
• We have discovered 3 types of plate movement
• All three can cause Earthquakes
• Divergent – ( plates moving apart)
• mid-ocean ridges, new ocean floor and rift
valleys form from these
• Convergent (move together)– ocean trenches
and most mountains form from these
• Transform (or) Strike Slip Boundaries
(move side to side) Only form earthquakes.
Divergent Boundary
Rift Valley
Two types of Convergent Plate
boundaries
• The boundary
where the two
continental plates
meet is called a
COLLISIONARY
boundary.
• Creates Folded
mountains and
earthquakes
Subduction Boundary
• A special type of convergent plate boundary
• In locations around the world, ocean crust
subducts, or slides under, a continental plate.
• This creates the geologic features we see
below
Subduction in Action
Transform boundaries –Or
A Strike Slip fault (also called a
lateral fault), They don’t create
or consume crust. Rather, two
plates move against each other,
building up force, then releasing
this force in a sudden and often
violent jerk.
This sudden jerk creates an
earthquake.
Earth’s Weather is Created by
Convection Cells
Convection Cells are what
power plate movement.
Do you know what’s happening
here?
Is that happening in this picture as well?