Earth Science Plate tectonics Why have all the mountains not worn away by now?

Mt. Everest- it’s still getting bigger!

Plate Movements There are two types of crust: OCEANIC and CONTINENTAL –If you pushed these two types of plates together, which do you think would go under, and which would go over? The faster moving, denser one would go under. But which is which?

The Plates Oceanic Plates are usually denser, darker and below sea level. So Continental plates must be….?

Where are the Plates? There are 7 MASSIVE plates 10 MEDIUM size plates And about 60 TINY ones. Can you spot them?

Types of Movements Diverging- also known as “Constructive Boundaries” Converging- also known as “Destructive Boundaries”

Types of Plate Boundaries What is an example of a Constructive Boundary? That’s right- Seafloor Spreading- lava comes out of the seafloor and then cools to form new crust, pushing the plates apart. There is a country where this can be seen, what is it? Well done if you guessed Iceland!!

Types of Plate Boundaries ICELAND: It’s growing 2 to 5cm wider per year!!

Types of Plate Boundaries What is an example of a Destructive Boundary? Remember, they are the same thing as Converging Boundaries! See if you can guess from the next slide…

Types of Movements What usually happens at Converging Boundaries?

Types of Movements What usually happens at Converging Boundaries? A convergence is a kind of “crash”. So when two things crash, either- One goes under, the other goes over (this happens if they are different densities; or if they are the same density- They “mash up” as the impact squashes them- makes mountains!

Destructive Boundaries Ocean crust is forced under the Continental crust, into the Asthenosphere. This is known as SUBDUCTION

So the Earth must be growing? Dense heavy oceanic crust can be subducted below less denser continental crust. The friction melts rock This magma rises through the crust to form new volcanoes This is happening in South America (The Andes) The Mariana Trench is the deepest ocean discovered- weird fish!

Or.. Continents Collide! Eventually when plates move together the continental crust collides The heat and pressure make metamorphic rock It also pushes and folds the rocks into high mountains The Himalayas rise to 8848m and are still growing today

Transform Boundaries Two plates sliding past each other. They move slowly, gripping each other, until the pressure builds up… They suddeny slip past each other, QUICKLY They’re not usually one crack, but many. New Zealand, Japan, California