PLATE TECTONICS

QUICK REVIEW: EARTH’S STRUCTURE

CRUST

MANTLE

CORE

QUICK REVIEW: EARTH’S STRUCTURE

CRUST: Top layer, rockyMANTLE: middle,Hot, rock & metal

CORE: innermost,Very hot, very denseIron & NickelPartly 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:

DivergentConvergentTransform

Convergent boundariesOccur when plates crash into each otherExample: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 boundariesOccur when plates move apart as new

rock is pushed up from mantleSea-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 BoundariesAnd, new crust is formed from cooling magma at Divergent Boundaries

Transform BoundariesPlaces 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 MOVINGDOES 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 PLATES30 MILLION YEARS AGO

THE EARTH’S PLATES65 MILLION YEARS AGO

THE EARTH’S PLATES140 MILLION YEARS AGO

THE EARTH’S PLATES200 MILLION YEARS AGO

This “super-continent” was called Pangaea

THE EARTH’S PLATES100 MILLION YEARS IN FUTURE?

ACTIVITY• Plate tectonics puzzle