2. Learning Outcomes
You will be successful if you can:
• Describe the reasons as to why earthquakes
and volcanoes are unpredictable.
• Recall that earthquakes, volcanoes and
mountain building occur at the edges of
tectonic plates.
• Be able to describe how the movement of
tectonic plates contribute to the rock cycle.
3. The Earth’s outer layer is
made up of a dozen giant
SLABS of rock, and some
smaller ones.
These are called TECTONIC
PLATES.
4. There are more than 30 000 earthquakes
every year!
Usually ONE
of these is
very
destructive.
KOBE, Japan
1995
5. The tectonic plates can move in 3 ways:
MOVE AWAY from Earthquakes are common at all
each other. Usually moving plate boundaries. The
under the sea, at most destructive happen at
OCEANIC RIDGES. subduction boundaries: these
may cause TSUNAMIS.
PUSH TOGETHER in
a squashing
movement, making
mountains like the
Himalayas.
SLIDE PAST each
other, like the San
Andreas fault in
California.
9. A volcano is a vent (or valve) in the
Earths surface. It erupts magma,
which forms lava or ash.
They are also
common at PLATE
BOUNDARIES,
where the Earth’s
crust is stretched,
compressed or
uplifted.
10. Review
Crust Mantle Core
Heat Low density Tectonic plates
Africa S America Rock types
Oceanic Plate Fossils High Density
Subduction Earthquakes
Magnetic Continental Radioactive
reversal plate Decay
pattern
