From fifty to one hundred miles below the volcanoes is a place called the
Magma Chamber. Some parts of the volcano in the Magma Chamber are so hot
that it melts rocks that forms a gas. When two divergent boundaries separate,
more gas gets into the Magma Chamber. That's what makes a volcano erupt.
Shield volcanoes have gentle slopes, like a shield, because they are made
of many layers of a kind of volcanic rock that flows easily when melted.
This kind of rock is called Basalt. When it flows out of the vent it forms
thin layers sloping away from the crater. Some shield volcanoes get to be
very large. The volcanoes which make up the islands of Hawaii are shield
Cinder Cones are made of bits of a kind of volcanic rock called Andersite.
Sometimes there are bits of Basalt, too. These bits of rock are called cinders.
They may be tiny, like ash, or larger like gravel. They get blown out of
the vent and harden in the air. When they land, they pile up around the crater
to form a steep cone. Cinder Cones are often smaller than Shield volcanoes,
and they wear away easily.
Composite Cones are made of layers of cinders between layers of lava. the
layers of cinders make the sides steep, and the layers of hardened lava keep
them from wearing away fast. Many famous volcanoes like Mt. St. Helens in
the state of Washington are Composite Cones.
Volcanoes are erupting all over our restless earth every day. Recent erupting
volcanoes include Axial Seamont, erupting January 25-28, 1998 at the location
of 45.55N, 130.00W. In Sakura-Jima, Japan a volcano erupted on January 24,
1998 at 31.58N, 130.67E. Volcanoes can be found on almost every
Click on each continent to learn about volcanoes
in the area.