Lesson 1 Earth
A VOLCANIC ERUPTION
A volcano can look like an ordinary mountain until it erupts. The first warning sign for a
volcanic eruption are earthquakes. These earthquakes build up from minor to
major strength and occur due to the pressure building up inside the magma chamber, deep
within the volcano.
As the magma (melted rocks)
forces its way up through the
cracks in the Earth’s surface the
earthquakes build in intensity.
When the magma reaches the
surface it releases an enormous
explosion
which
causes
ash
(finely powdered rock that looks
like dark smoke coming from the
volcano),
cinders
(bits
of
fragmented lava), and pumice
(light-weight rock that is full of air bubbles and is formed in explosive volcanic
eruptions) to be thrown hundreds of meters into the air.
After the initial eruption happens it releases the pent up pressure of the volcano for a
short time until the magma reaches the surface. As magma comes out of the volcano it
changes into lava, which can be fast flowing or can move very slowly. This lava is really
hot, burning everything in its path. As the lava cools down it becomes a solid rock called
igneous rock.
When enough of the magma is released and there is no longer any pressure the volcano
becomes dormant, occasionally letting off steam and other gases. With time vegetation
grows back and often the traces of the eruptions covered.
Julie Woodcock