3. 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!
4. 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.
5. Or they can form HALF-GRABENS
These features build MOUNTAINS.
6. Which type of Graben is this?
This type covers an
area THIS big in the
USA (known as
Basin and Range)
7. 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 As we go through the
next few slides, write
•Continental – Continental down an example of
each type/
•Oceanic - Oceanic combination.
8. 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.
9. Andes Mountains
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.
10. 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.
11. 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!
12. Continent-Continent Collision:
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.
13. 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.
14. The San Andreas Fault
• 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).
15. 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?
16.
17. 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
18. Check your answers
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.
19. 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?
20. Copy the table below and use the information from the lessons to:
21. HOMEWORK
By 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.
