Transcript Plate Tectonics

Plate Tectonics
ESPS 2015
Hagen
ESSENTIAL QUESTIONS
Explain and give evidence of Continental Drift
Describe the process of sea-floor spreading
List and analyze the 3 types of boundaries
SPONGE ACTIVITY
Give one piece of scientific evidence that is true
and one piece that is false
https://www.youtube.com/watch?v
=zocutif0cQY
Why do Continents Drift?
Earths crust is not a uniform covering, its made of 8 major
and minor plates – North American/Pacific/Juan de Fuca
plate
As these plates move, the continents are rafted along
passively (like a piggyback ride on top of Aesthenosphere,
which is on top of the mantle
1960’s the Theory of Continental Drift or Plate tectonics
became established
Continental Drift
1900’s-----1912
Alfred Wegener first proposed the theory of continental
drift. Wegener provided evidence that the there was once a
giant land mass, but did not explain how the continents
moved
His theory stated that the continents used to be one large
super-continent or “Pangea” and through time they have
broken apart and moved.
Continental Drift
• Wegener hypothesized that there was a gigantic supercontinent 200
million years ago, which he named Pangaea, meaning "All-earth".
EVIDENCE!!!!!! Give some space below each type of evidence
1. Continental Fit – Example of South America and Africa.
2. Fossils – Fossils in S. America and Africa Dated the same
3.
Glacial Patterns – Glacial scars on N. America and Asia/Europe that
had the same dates
http://www.classzone.com/books/earth_science/terc/content/
visualizations/es0806/es0806page01.cfm
Continental Drift Evidence:
When you look at a map you can
see the how the edges of continents
fit together like a puzzle
The theory of continental drift
states that continents have
moved from their current
locations and will continue to
move over time
Tectonic plates move with
speed ~1 cm/year to ~10
cm/year.
The speed is different from
plate to plate, and can depend
on how much active the plate
currently is.
Continental Drift Evidence
Fossils show that the same reptiles
lived on different continents despite
being so far apart. Plants too.
Continental Drift Evidence
Geological features show
that colder climates were
once warmer and warmer
climates were once cold
(e.g. glaciers and plant
fossils)
Rock clues show the same
rock features on different
continents
Evidence Activity
Cut out continents and then
paste them on the map
Be sure to match up fossil
evidence with rock and desert
evidence
Homework tonight
Case of the Mesosaurus
Continents today
Seafloor Spreading
At one time the bottom of the
ocean was a foreign as space;
with the discover of using
sound waves to map the ocean
floor lead to amazing
discoveries
A system of ridges and valleys
was discovered running through
the center of the Atlantic Ocean
Sea floor spreading is the
process by which new sea floor
is created, pushing two tectonic
plates further apart
Seafloor Spreading
As scientists began
studying the ages of the
ridge they found that as
they moved towards the
center of the ridge the
rocks got younger and
younger
This means that new rock
was forming at the center
of the ridge and being
pushed outwards as new
rock filled in
Seafloor Spreading
Evidence of Seafloor spreading:
The rocks age as they
move away from the ridge
The new rock contains iron
which is magnetic; over the
course of the Earth’s history
the magnetic poles have
switched; when the iron in
the rock cools it lines up
with the pole; the iron
samples have reversed
several times
Theory of Plate Tectonics
With the discovery of seafloor
spreading showed more than
why the continents are the way
they are – they showed why we
have the geological features that
we do
The Theory of Plate Tectonics
combines continental drift and
seafloor spreading and states
that there are several plates that
move around the mantle of the
Earth
Theory of Plate Tectonics
Where two plates interact
are called plate boundaries
3 types of boundaries are
called divergent,
convergent and transform
These boundaries form
earthquakes and volcanoes
Divergent boundaries
move apart and cause
seafloor spreading
Theory of Plate Tectonics
Convergent boundaries move
together and form volcanoes
Ocean – ocean boundaries
(hot spots)
Ocean – continental
boundaries (magma
chambers)
Continental – continental
boundaries (mountains)
Transform boundaries move
past one another and form
earthquakes
Theory of Plate Tectonics