This is a
site about volcanoes and the damage they cause. A volcano is an opening
in Earth's surface. It forms a mountain when layers of lava and volcanic
ash erupt and build it. Most of Earth's volcanoes are not active,
or they are dormant. But lots of volcanoes are active, most spew
smoke, ash, steam, or flows of lava. Some eruptions emit toxic fumes
that cause a lot of damage to the plants and animals on Earth's surface.
Those fumes could be the cause of loss of the ozone layer.
How
Volcanoes Form and Erupt
Volcanoes
erupt because of heat and pressure that melts rock and forms magma.
Rocks that are deep into earth's mantle are already melted. Other
rocks are hot enough that a tiny rise in temperature or drop in pressure
could melt them. Magma is slowly forced up toward earth's surface.
After millions of years the magma pushes its way up to earth's surface,
it flows out through an opening called a vent. When it cools it makes
layers that form a volcano. After a while pressure builds up and
the magma rises.
Where
Volcanoes Form
Volcanoes can form in three different kinds of places. Each of the
three places are directly related to the movement of Earth's plates.
Volcanoes form at divergent boundaries, plates that are moving apart.
Volcanoes also form at convergent boundaries, plates that move together,
and they also form at places called hot spots.
Divergent boundaries are plates that move apart. The Mid Atlantic
Ridge sits on a divergent boundary. When they move apart they form
deep cracks called rifts. Magma flows up the rifts and quickly cools
because of the sea water. The layers of magma rise and build on the
sea floor. If the volcano erupts above sea level it can form an island.
Convergent boundaries are boundaries that move together. Earth's
plates move together at convergent plate boundaries, one of the plates
slide under each other and magma is formed in the subduction zone.
The under lapping plate gets deep and hot enough that it partially melts.
The magma is forced upward and volcanoes form.
Different
Volcanoes Fuji
The volcano Fiji is located in Honshu, Japan. It is located at 35.4N
and 138.7E. Its elevation is 3,776 meters. Fuji has erupted
at least 16 times since 781 AD. The most recent eruption was in 1707
to 1708 from a vent in the southeast side of the cone. This volcano
caused a lot of damage. The eruption ejected 0.8 cubic km of ash.
Fuji also had two other eruptions, one is 1050 BC and the other in 930
BC. They were very large eruptions and caused a lot of damage.
Kikai
Kikai is in Kyushu, Japan, it is located at 30.8N and 130.3E. Kikai
stands at an elevation of 717 meters. Kikai is a submarine
caldera volcano, three small islands surround it (parts of the caldera
rim). The rim submerged above sea level to from the islands.
the most recent eruption was about 6,300 years ago, it was the largest
eruption on Earth in the last 10,000 years. It was estimated that
about 150 cubic km of ash was emitted .
