Patterns of the Plates
Earthquakes, volcanoes and fold mountains all occur in similar areas. They occur in long narrow
bands thousands of miles long but only hundreds of kms wide. These narrow bands are the Plate
Boundaries.
Over millions of years the continents have drifted apart from an original supercontinent called
……………. The idea of Continental Drift was first put forward by Alfred Wegener in 1912. His
evidence came from things like:
 The similarity in the shape of the coastlines of S. America and Africa
 Similar glacial deposits from 290 million years ago are found in S. America, Antarctica
and India
 Similar geological sequences are seen in Scotland and eastern Canada.
 Fossil remains are found on different continents
 Coal reserves are found in Antarctica - the climate there must have been much warmer.
The more modern theory of Plate Tectonics comes from much later – 1960s. Supporting
evidence came from:
i)
discovery of the mid-Atlantic Ridge in 1948
ii)
studies of palaeomagenetism in the `1950s
iii)
sea floor spreading – in 1962 Harry Hess confirmed that the newest rocks were in
the middle of the Atlantic (near Iceland) and got older to the edges e.g. USA. He said
that the Atlantic could be widening at 5cm/year.
If the Atlantic was getting wider, and if the earth was not getting bigger, then somewhere
else old crustal rocks must be being ‘eaten up’. Evidence for this came from the fringes of
the Pacific Ocean.
Many of the oceans are under 200 …………………. Years old.
Some of the plates are only oceanic crust e.g. …………………….
Others carry oceans and continents on their back e.g. ……………………..
Continental plates (40kms) are much thicker than ocean plates (10kms) and are thickest under
………………………………. An example of thick continental crust is ………………………
The ………………….. crust is much older than the …………………. Crust.
The crust and the top part of the mantle makes up the lithospheric plates which float on the
underlying ……………………………………
 The main plates are :
1.
2.
3.
4.
5.

1.
2.
3.





6.
7.
8.
The different types of plate boundaries are ….
where two plates converge (move together)
where two plates diverge (move apart)
where two plates slide past each other
Mid-Ocean ridges are found at ……………. Plate boundaries
Mid-Ocean ridges have volcanoes that release …………….. lava
The Pacific Ring of Fire is a …………….. Plate Boundary
The volcanoes of the Ring of Fire have volcanoes that release ……………… lava
Young Fold Mountains are found at certain types of …………….. Plate Boundaries where
two plates …………………………


The San Andreas Fault is an example of a ………………… Plate Boundary and has no
volcanoes – just earthquakes.
The Main Plates: Add some arrows to show direction of movement.
Convergent boundaries = Destructive Plate Boundaries: e.g.
Divergent Boundaries = Constructive Plate Boundaries e.g.
Transform Faults = Conservative Plate Boundaries e.g.
The Main Young Fold Mountains Andes, Rockies, Alps, Pyrenees, Atlas, Caucasus,
Hindu Kush, Himalayas, Southern Alps
Distribution of Volcanoes: Note the well defined arcs such as in the Aleutians, central and
western North and South America, and the east Pacific all of which correlate with the locations
of deep earthquakes. Some volcanic regions such as the Hawaiian Islands are isolated. An
interesting region of substantial volcanic activity is east Africa, a region also experiencing
extensional faulting.
Also label the Pacific Ring of Fire and the Mid-Atlantic Ridge
Distribution of Earthquakes (seismic activity) 90% of all earthquakes occur along plate
margins and by far the greater amount of energy released as seismic waves comes from
subduction zones. Earthquake locations for events between 1965 and 1995. The red dots are
shallow earthquakes, the green are intermediate depth, and the blue and purple are deep.
The map above shows the distribution of earthquakes with magnitudes greater than 5.0 that
occurred between 1965 and 1995. Earthquakes deeper than 500 km are restricted to only a few
regions surrounding the Pacific and part of the Indian oceans. Shallow earthquakes are located
over much of Earth, but are most common in narrow belts.
The deepest earthquakes are located on the rim of the Pacific Ocean (those regions also have
shallow earthquakes, but on this map their symbols are hidden beneath the deep events).
 The deepest earthquakes occur ….

Shallow focus earthquakes occur ….
Colour code the statements
- those about The Distribution of Earthquakes and Volcanoes
- those about places which do not have Tectonic Hazards (i.e. no earthquakes or volcanoes)
- those about plate boundaries and zones of activity
Can you name some of the types of Plate Boundaries (add these to the statements)?
Hawaii is a Hot Spot where volcanoes occur
in the middle of a plate not on a Plate
Boundary
The Cascade Range of volcanoes are in
Washington State in the NW of the USA.
Volcanoes and earthquakes often occur in
the same places and are usually found in
long narrow belts
Volcanoes are found in the middle of the
Atlantic Ocean forming a line running from
north to south.
The main zone of activity lies along the west
coast of the Americas and among the islands
of the Pacific and Indian Oceans
Another belt goes down the middle of the
Atlantic Ocean
Volcanoes and earthquakes happen along
On the west coast of South America, the Nazca
the west coast of North America
Plate and the South American Plate move
together
There is a lot of volcanic activity on Iceland
One belt runs all the way round the Pacific
Ocean and is called the 'Ring of Fire'.
A belt of volcanoes and earthquakes is
located along the west coast of South
America
The North American and the Eurasian Plates are
moving away from each other.
Australia is located in the middle of the IndoAustralian Plate
Zones of activity are found around the edges of
many of the world's plates.
The east coasts of North and South America
are not close to zones of activity.
Many earthquakes happen in the Himalayan
Mountains to the north of India.
The Eurasian and Indo-Australian Plates are
moving towards each other.
No volcanoes or earthquakes are found on the
east coasts of North and South America.
Another belt runs through the islands of the
Indian Ocean.
The San Andreas fault in California has
earthquakes and no volcanoes as two plates
slide past each other.