Download Crust Solid surface, with great expanses of wate Mantle

PLATE TECTONICS
QUICK REVIEW: EARTH’S
STRUCTURE
CRUST
MANTLE
CORE
QUICK REVIEW: EARTH’S
STRUCTURE
CRUST: Top layer,
rocky
MANTLE: middle,
Hot, rock & metal
CORE: innermost,
Very hot, very dense
Iron & Nickel
Partly liquid
NEW INFO: EARTH’S
STRUCTURE
TECTONIC PLATES – sections of the crust and
upper mantle that are stuck together
TECTONIC PLATES – “float” on top of the rest
of the mantle and are slowly moving
(a few centimeters per year)
7 major plates on the Earth-
the African, North American, South
American, Eurasian, Australian,
Antarctic, and Pacific plates
+ several smaller plates
THE EARTH’S TECTONIC PLATES
The place where the two plates
meet is called a
plate boundary
There are 3 TYPES of Plate Boundaries.
THE EARTH’S
TECTONIC PLATES:
3 Types of Boundaries:
Divergent
Convergent
Transform
Convergent boundaries
Occur when plates crash into each
other
Example:
Indian Plate is crashing into Eurasian
Plate
Subduction occurs at
Convergent Boundaries
• When one plate slides underneath another
• Crust (solid) melts back into magma
(liquid)
Ring of Fire - Japan
• Sits where Philippine plate and Pacific
plate are subducting under Eurasian plate
• Feel earth tremors every few weeks
• Lots of earthquakes, volcanoes and
tsunamis (tidal waves)
• 2011 Tsunami in Japan caused by
underwater earthquake
Ring of Fire
Divergent boundaries
Occur when plates move apart as new rock
is pushed up from mantle
Sea-floor Spreading
Mid-Atlantic Ridge is an
example of a divergent
boundary
• Under Atlantic ocean
• South American Plate is pulling away from
African Plate
• Magma (liquid) comes up from mantle and
cools to form new crust (solid rock)
• Volcanic mountains form deep underwater
• Extra heat at great depths provides home
to many strange animals
So, old crust subducts and melts into magma
at Convergent Boundaries
And, new crust is formed from cooling magma
at Divergent Boundaries
Transform Boundaries
Places where plates slide past each other
are called transform boundaries
Transform Boundaries
• San Andreas Fault in
California
– 5 Major Earthquakes in
past 20 years!
Loma Prieta Earthquake 1989
WHAT HAPPENS AT BOUNDARIES?
MOUNTAINS – at convergent boundaries – one of the plates is pushed
upwards and forms Mountain ranges!
EARTHQUAKES – Plates are giant slabs of rock pushing on each other.
They do not glide by smoothly! Sometimes they build up huge amount of energy
and then slip violently – an Earthquake!
VOLCANOS – at convergent boundaries – one plate subducts and the
pressure melts it! The newly formed liquid rock (magma) can be pushed to the
surface – a Volcano!. At Divergent boundaries, magma is always flowing out – a
slow stead oozing volcano!
TSUNAMI– when earthquakes occur under water – they can trigger huge
tidal waves - Tsunamis
WHAT HAPPENS AT BOUNDARIES?
So, even thought he plates are only
moving a few centimeters per year –
that much Earth moving at all has a
lot of energy and can release it in
Very dramatic ways
Tidal wave caused by underwater earthquake
• types of boundaries
WHAT HAPPENS AT BOUNDARIES?
HEY WAIT!
IF ALL THE PLATES ARE MOVING
DOES THAT MEAN THE
CONTINENTS ARE MOVING TO?
DO NOT TRY TO COPY PICTURES ON NEXT SLIDES
– BUT DO TAKE SOME GENERAL NOTES
THE EARTH’S PLATES TODAY
THE EARTH’S PLATES
30 MILLION YEARS AGO
THE EARTH’S PLATES
65 MILLION YEARS AGO
THE EARTH’S PLATES
140 MILLION YEARS AGO
THE EARTH’S PLATES
200 MILLION YEARS AGO
This “super-continent” was
called Pangaea
THE EARTH’S PLATES
100 MILLION YEARS IN FUTURE?
ACTIVITY
• Plate tectonics puzzle