}
Volcanoes are mountains where hot, melted rock which
we call lava comes from the magma chamber under the ground and out through the
crater at the top – This is called an active volcano.
The materials that pour out is lava, steam, Sulphur gas,
ash and broken pieces of rock.
The name “volcano” has its origin from the name of Vulcan, a god of fire in Roman mythology.
Underneath
the ground the pressure builds up around the molten rock and it has to escape
somewhere. It is forced through the
narrow cracks in the crust which is called the fissures. If the magma comes out of the volcano, it is
called lava.
The lava can be between 700 to 1200 degrees C in temperature.
We have more than 1500 active volcanoes in the world and there are even more underneath the sea.
The tectonic plates of the Earth’s
crust fits together, but they also move.
Once they collide and the one part slides on top of the other, the magma
is squeezed out.
Around the Pacific Ocean there is an area called the ‘Ring of Fire’ and most of the world’s volcanoes are found here.
The
Earth’s crust is made up of huge slabs called plates, which fit together like a
jigsaw puzzle. These plates sometimes
move. When two plates collide, one section slides on top of the other, the one
beneath is pushed down. Magma is squeezed out.
The largest volcano (and mountain) in our Solar System is Olympus Mons on the planet Mars. The volcano is 17 miles (27 km) tall and over 320 miles (520 km) across.
Mauna Loa is one of the five volcanoes that form the island of Hawaii. It is 60 miles long and 30 miles wide, it makes up half of the entire island. Mauna Loa, and Kilauea are the only active volcanoes. Mount St. Helens, in the state of Washington, is one of more than 100 active or potentially active volcanoes in the continental United States, Alaska, and Hawaii. Only Indonesia and Japan have more.
A volcano can be in one of three
states – active, dormant or extinct. One
that has erupted in the last 1000 years and can erupt again is considered
active. One that has not erupted in the
last 1000 years but still have the potential to erupt one day is called dormant
and a volcano that will never erupt again is called extinct.
Watch this video for more info on volcanoes.
Volcanic ash is very good for farmlands in surrounding areas. The nutrients present in volcanic ash help to make the land very fertile. The Maleo bird actually incubates its eggs using the heat from the volcanic sand.
For fun build your own volcano- watch the video for some ideas.