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Types of Volcanoes
Some of our Earth’s most spectacular mountains are large composite volcanoes.
This type of volcano is built of alternating layers of lava flows, volcanic ash and cinders.
Mount Rainier and Mount Saint Helens in Washington state, Mount Shasta in California,
Mount Vesuvius in Italy and Mount Fujiyama in Japan are all composite volcanoes.
Some are active while others are currently inactive (dormant). Find these mountains on
the classroom map.
A sleeping giant awoke on May 18, 1980. An enormous blast blew off the top and
side of this mountain in Washington state. There had been warnings of volcanic activity
in the form of earthquakes and venting of steam for two months. Mount St. Helens had
been dormant since 1831.
Mt. St. Helens blew a cloud of rock, ash and gas which was spread over a large
area, killing trees, animals and at least 70 people. This large volcano is a relatively new
mountain. Geologists estimate its age to be only about 40,000 years old. During the past
4,500 years, Mt. St. Helens has been the most explosive volcano in the continental United
States. Its eruption was not unexpected.
Gr. 4 Earth, Wind & Fire
1 of 3
Mesa Public Schools • Mesa, AZ
Types of Volcanoes
Cinder cone volcanoes are the simplest type of volcano. They are built entirely of
cinders and other igneous (volcanic) material. The hot, molten lava is exploded from the
vent of the volcano by the build up of gas inside the volcano. As this gas-filled lava is
blown violently into the air, it breaks into many small pieces. These pieces harden and
fall around the vent to form a cone.
On February 20, 1943, a farmer was plowing his corn field in a village called
Paricutín, located near Mexico City, Mexico. He noticed a thin wisp of smoke rising from
the ground. The ground was becoming very hot. The farmer watched the smoke until
about 4 o’clock in the afternoon. At that time small explosions started to occur. Smoke
and ash were rising from the hole in the ground and a cone began to form. Two days
after the eruption began, the first lava flowed from a fissure (crack in the earth).
For 9 years the activity from the volcano continued. Scientists from many parts of
the world came to study this active volcano. It eventually covered about 100 miles with
ash and destroyed the town of San Juan. Then, as quickly as it had started, it stopped.
Now Paricutín is just another small, inactive volcano. Geologists were able to learn a
great deal about volcanoes from studying Paricutín while it was active.
Gr. 4 Earth, Wind & Fire
2 of 3
Mesa Public Schools • Mesa, AZ
Types of Volcanoes
Shield volcanoes are built almost completely of fluid lava flowing out in all directions from a central summit vent, or group of vents. This produces a broad, gently sloping cone with a shape much like that of a warrior’s shield. The volcano builds up slowly. Each deposit of the hot fluid lava spreads out over great distances and then cools in
thin sheets. These building cycles can continue for thousands and thousands of years.
The Hawaiian Islands are peaks of a long line of shield volcanoes called the
Hawaiian Chain. Some of these volcanoes project above the ocean creating islands while
others remain below the surface. Most of these are found on the Pacific Plate. The big
island of Hawaii is the upper part of five different shield volcanoes.
Mauna Loa and Kilauea are two very active volcanoes on the island of Hawaii.
Mauna Loa is the largest and most active shield volcano in the world. When Kilauea’s
magma rises up from within the mountain, it spills out and forms a lava lake. Sometimes
this lava lake spills over its sides, and other times the lava will just sit and bubble.
Sometimes the lava will disappear altogether.
Gr. 4 Earth, Wind & Fire
3 of 3
Mesa Public Schools • Mesa, AZ