Catchy video rap!

What type of plate movement is this weirdly ominous video describing?

It is describing plates moving AWAY from each other. These are known as DIVERGENT or

CONSTRUCTIVE boundaries

Sketch me and label me!

Stuff to know about divergent plates:

•As plates diverge, they can form Grabens if they are on Continental crust. This means that some of the land drops as the crust of the earth stretches.

Or they can form HALF-GRABENS

These features build MOUNTAINS.

Which type of Graben is this?

This type covers an area THIS big in the

USA (known as Basin and Range)

If you think logically, these aren’t TOO tricky!

There are two types of crust, so there are 3 types of convergent boundary:

•Oceanic – Continental

•Continental – Continental

•Oceanic - Oceanic

As we go through the next few slides, write down an example of

each type/ combination.

Ocean-Continent Collision:Underneath the ocean water there are a number of long, narrow, curving trenches thousands of kilometers long and 8 to 10 km deep cutting into the ocean floor. Trenches are the deepest parts of the ocean floor and are created by subduction.

Ocean-Continent Collision:

Off the coast of South America, the oceanic Nazca Plate is pushing into and being subducted under the continental part of the South American Plate. At the same time, the South American Plate is being lifted up, creating the Andes Mountains.

Strong, destructive earthquakes and the rapid uplift of mountain ranges are common in this region. Such earthquakes have been known to jolt the land up several meters.

Andes Mountains

Ocean-Ocean Collision:

When two oceanic plate collide, it can result in the formation of volcanoes, too. One oceanic plate sinks beneath the other, and over millions of years, the erupted lava and volcanic debris pile up on the ocean floor. Finally, a volcano rises above sea level to form an island volcano. Such volcanoes are typically strung out in chains called island arcs.

This is how the Aleutian Islands have formed and why they experience numerous strong earthquakes.

Continent-Continent Collision:

The Himalayan Mountains were created when two continental plates met head-on,and neither was subducted. Continental rocks are relatively light and, like two colliding icebergs,resist downward motion. Instead, the crust buckled and was pushed upward and sideways. Viola!

Mountains!

India collided into Asia 50 million years ago, causing the Eurasian Plate to crumple up and override the Indian Plate.

After the collision, the slow continuous convergence of the two plates over millions of years pushed up the Himalayas and the Tibetan Plateau to their present heights.

The Himalayas, towering as high as 8,854 m above sea level, are the highest continental mountains in the world.

Continent-Continent Collision:

Most transform boundaries are found on the ocean floor. A few occur on land, an example is the San Andreas fault in California. Transform boundaries are the result of two plates sliding past each other.

• Stretches about 1,300 km long and in some places tens of kilometers wide.

• Slices through two thirds of the length of California.

• The Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr.

• Land on the west side of the fault (on the Pacific Plate) is moving in a northwesterly direction RELATIVE to the land on the east side of the fault zone (on the North American Plate).

The San Andreas Fault

Sometimes a plate boundary can contain more than one type of movement. Sounds weird?

These plates are divergent, but what is happening at this little bit here?

Shade the cards that are about the world pattern of earthquakes and

volcanoes in red. Then shade those that are about tectonic

plates and active zones in blue. Choose a red card. Find a blue card

that can be linked with it. Keep going until you have matched all of

the statements

Active zones are found around the edges of many of the world’s tectonic plates.Earthquakes and volcanoes occur in linear patterns in some parts of the world.

In places, the North American and Pacific Plates are moving past each other.Volcanoes and earthquakes occur along the west coast of North America.

Many volcanoes and earthquakes are clustered together on islands and continents around the edge of the Pacific Ocean.Around the edge of the Pacific plate is an active zone called the ‘ring of fire’.

The North American and Eurasian plates are moving away from one another.Volcanoes can be found in a line running north to south down the middle of the Atlantic Ocean.

Australia is found in the middle of the Indo-Australian plate.Volcanoes and earthquakes are not found in Australia.

The east coasts of North and South America are not close to active zones.There are no volcanoes or earthquakes on the east coast of North or South America.

There is an active zone where the Nazca and South American plates move together.A belt of volcanoes and earthquakes is located along the west coast of South America.

The Eurasian and Indo-Australian plates are moving towards each other.Many earthquakes happen in the Himalayan mountains to the north of India.

Check your answers

Look at the map below. It shows recent volcanoes and earthquakes. Volcanoes are shown in blue, earthquakes in red. Are they scattered randomly, or is there some kind of pattern? If so, can you explain why?

Copy the table below and use the information from the lessons to:

HOMEWORKBy this time next week I’d like you ALL to have

pictures of the three different types of convergent boundary to stick into your books, plus a sketch of a

transform boundary.

DRAWN. By your own fair hands.(Remember: oceanic-continental, oceanic-oceanic, and continental-

continental)

The library has books, or if you don’t have access to internet at home you are welcome to attend the Humanities Achievement session on

Thursday in H12 at 3pm. There are netbooks available. There are also textbooks in the cupboard in H12, or the electronic copy on Fronter.