Transcript First Theory – 1880`s

Geology
Rocks!
Development of
Plate Tectonic
Theory
9-12 Science Std: Geo 3a, b
Plate Tectonics: The study of plate motion
Tectonics – derived from Greek word
“tekton” which means “Builders”
Refers to “buildings” or features on
Earth’s surface created or “built” due to
deformation caused by plate movements.
This shows the Earth’s changing
landscape due to the motion of plates at
their boundaries
First Theory – 1880’s
2 features on the earth started the
development of the plate tectonic theory
Similar fossils on
different continents
Origin of Mountain
Ranges
First Theory – 1880’s
Mountain ranges formed
when surface of earth
cooled when formed
Austrian geologist
Edward Suess
This would cause parts of the sea
floor and continents to rise and shrink
Land bridges would form between
continents that are now under water
Like an apple wrinkles and
folds when it dries out
Would explain why similar fossils
are found on different continents
This theory worked for a while………..
But people still had some questions
about how it worked
After a while, scientists found some
evidence that the “shrinking apple” theory
was wrong……
Radioactive Heating – The
earth would never cool
down enough…….
Compression of Alps – not
uniform wrinkles, but
folding of the rock layers
In 1912, German geoscientist Alfred Wegner
proposed a different hypothesis…..
It started with a huge “supercontinent” called “Pangaea”
Ok, so what evidence do you have for
your hypothesis…?
The continents fit
together like a
jigsaw puzzle…….
Ok, so what evidence do you have for
your hypothesis…?
And there were
similar rocks,
geologic structures
and fossils on
opposite sides of
the Atlantic Ocean
“Great Idea – but How did the
continents move?”
Wegner’s Hypothesis - continents moved by slow fluid flow
of material below Earth’s lithosphere
He said that the movement was very slow and has been
happening over millions of years
“Great Idea – but How did the
continents move?”
Wegner’s Hypothesis - continents moved by slow fluid flow
of material below Earth’s lithosphere
He said that the movement was very slow and has been
happening over millions of years
“Great Idea – but How did the
continents move?”
Wegner’s Hypothesis - continents moved by slow fluid flow
of material below Earth’s lithosphere
He said that the movement was very slow and has been
happening over millions of years
“Great Idea – but How did the
continents move?”
Wegner’s Hypothesis - continents moved by slow fluid flow
of material below Earth’s lithosphere
He said that the movement was very slow and has been
happening over millions of years
“Great Idea – but How did the
continents move?”
Wegner’s Hypothesis - continents moved by slow fluid flow
of material below Earth’s lithosphere
He said that the movement was very slow and has been
happening over millions of years
Now we have evidence to show
Wegner’s theory was right
Had to wait for 1940’s to prove
the theory was right…
The submarines needed
very accurate maps of
the ocean bottom
When they made the
maps, they found midocean ridges….
Now we have evidence to show
Wegner’s theory was right
Outlines of continental plates Similar fossils and rock types
So now it’s your turn
If you have your text – turn to page 110
We will be working on Ch 2 Act 5 Step 3
Your job will be to take the world as you know it now…..
So now it’s your turn
If you have your text – turn to page 110
We will be working on Ch 2 Act 5 Step 3
And turn it into the supercontinent “Pangea” of long ago