Grade 6 Earth's Surface 2
Wk 12 – 6/8
Earth's Surface – Earthquakes and Volcanoes
Write or draw everything you know about earthquakes.
Earthquakes
If you push a ruler very hard on both ends, it will break in two. Earth's
plates work in a similar way. If there is lots of pressure, the rock surface
will break. When the rocks break, a fault is
formed.
A fault is a break in Earth's crust where rocks
can slide past each other.
As Earth's plates move, pressure builds up along
the fault lines. The rocks bend and stretch, nearly like a rubber band. If
the rocks stretch too far, they will snap and energy will be released as they
suddenly slide past each other.
The snap and slide of rocks as energy is released in Earth's crust is known
as an earthquake.
Earthquakes can happen close to Earth's surface or very deep inside the
crust or mantle. The point inside Earth where an earthquake begins is
called the focus. The point on Earth's
surface directly above the focus of an
earthquake is the epicenter.
When an earthquake begins, the energy
travels away from the focus in waves.
Cause and Effect
What causes an earthquake?
What might the effect be of a large earthquake?
Earthquakes
Cause
Effect
Volcanoes
Answer the following questions.
How many different types of volcanoes are there?
Do volcanoes always look like mountains?
How are some islands made?
Watch Magic school bus or
demonstration of erupting volcano.
Some mountains form when plates push together, but some form in another
way. Mountains called volcanoes form when
molten rock, or magma, is pushed to the
surface and builds up.
Most volcanoes are along the boundaries of
Earth's plates.
Volcanoes don't just happen on land, but in the water as well. Volcanoes can
even make islands, like Hawaii. Hawaii has many volcanoes that have been
erupting for a long time.
There are many types of volcanoes but we can put them into three basic
groups.
*Split into 3 groups and read about 1 type of volcano each. Using the
interactive whiteboard, explain about it using words and pictures.
Use the descriptions to draw
the volcano, using colour.
Shield Volcano
Shield volcanoes have a wide base, are slightly
domed and may erupt many times over millions
of years. Shield volcanoes erupt very slowly with
lava flowing out of them.
Composite Volcano
Are very large volcanoes with steep sides. They
erupt many times over millions of years pushing
rock, ash and lava into the air. We usually hear
about composite volcanoes the most.
Cinder Cone Volcano
Cinder cone volcanoes have steep sides. They
erupt quickly pushing only rock and ash into the
air. They don't grow very high because the rock and ash they are mad out
of erodes quickly.
Go back and check your answers to the volcano questions. Did you get
them right? If not write the correct answer next to your guess.
Draw conclusions
The black dots are where there have
been earthquakes. Why do you think
there
have
not
been
many
earthquakes in Australia?
My Dictionary
earthquakes: _________________________________________
fault: _______________________________________________
focus: ______________________________________________
epicenter: ____________________________________________
volcano: ______________________________________________
shield: _______________________________________________
composite: ____________________________________________
cinder: _______________________________________________
____________: ________________________________________