•What is a Volcano?
•How do volcanoes form?
•What are the 3 types of volcanoes?
•What is the Ring of Fire?
•How are volcanoes beneficial to Earth?
•A volcano is a vent (an opening
at the Earth’s surface) through
which which lava, hot gases, and rock
fragments erupt.
•Eruptions of volcanic mountains are
spectacular sights. In some eruptions,
huge fiery clouds rise over the mountain,
and glowing rivers of lava flow down its
sides.
•In other eruptions, red-hot ash and
cinders shoot out the mountaintop, and
large chunks of hot rock are blasted high
into the air.
•Some eruptions occur on volcanic
islands. Others occur along the
ocean floor, building up the sea bottom.
More than 80 percent of the earth's surface is volcanic in origin. The sea floor and
some mountains were formed by countless volcanic eruptions. It is said that gases
from volcanoes formed the earth's atmosphere.
A Volcanologist is a scientist who studies volcanoes. They investigate the nature and
causes of eruptions and have saved many lives in doing so.
Kanaga Volcano, Alaska
A basic volcano is made of a vent, a pipe, a crater, and a cone. As we learned earlier, a vent
is an opening in the Earth’s surface. The pipe is a passageway in the volcano in which the
magma rises through to the surface during an eruption. The crater is a bowl-shaped
depression at the top of the volcano where volcanic materials like ash, lava, and other
materials are released. When the lava and ashes have cooled, they form the cone. Layers of
lava alternate with layers of ash to build the steep sided cone higher and higher.
The gas-filled magma in the magma chamber is under great pressure
from the weight of the solid rock around it. This pressure causes the
magma to melt a tunnel in a fractured or weakened part of the rock.
The magma moves up through the tunnel to the surface. When the
magma nears the surface, the gases are released. The gas and magma
blast out at the vent. Most magma and other volcanic materials then
erupt through this vent. The materials gradually pile up around the
vent, forming a volcanic mountain, or volcano.
•There are more than 500 active volcanoes in the world. More than half of these
volcanoes are part of the "Ring of Fire," a region that encircles the Pacific Ocean.
•Earth's outer crust is divided into a number of rigid sections of rock, called
plates. The plates slide or drift about continuously over a layer of partly melted
rock. As the plates move, their boundaries collide, spread apart, or slide past
one another. Most volcanic eruptions occur at the plate boundaries or when two
plates move. Plates that are constantly moving and causing volcanic activity
form this“Ring of Fire”
Volcanoes are among the most destructive natural forces on Earth.
Since the 1400's, they have killed almost 200,000 people. But
volcanoes also produce benefits…
•Rocks formed from lava are commonly used in building roads that we drive on.
•In many volcanic regions, people use underground steam as a source of energy.
This is called geothermal energy and is used to produce electric power in such
countries as Italy, Mexico, and New Zealand.
•Weathered volcanic ash greatly improves soil quality believe it or not!
•In Reykjavik, Iceland, most people heat their homes with water piped from volcanic
hot springs.
Let’s Review
• Which of the following may build
up the land?
–A. A volcanic eruption
–B. flooding
–C. wind
–D. A hurricane
Let’s Review
SHORT RESPONSE
• We know that volcanoes can be
very destructive to Earth’s surface.
However, what are some of the
benefits of volcanoes?
Let’s Review
• What is the hot molten rock that comes
out of a volcano called?
– A. Sedimentary Rock
– B. Ash
– C. Vents
– D. Lava
Let’s Review
• Volcanoes can happen under water.
– True
– False
Let’s Review
• What do we call a volcano that will
never erupt again?
– A. Lazy
– B. Dormant
– C. Extinct
– D. Active