Volcanoes

6.2

What happens when a volcano erupts?

The magma in the asthenosphere is under great pressure. Magma rises into the cracks because magma is less dense than the crust.

Hot Magma

Cool Crust

As the magma rises toward the surface, less pressure is on the magma. This allows dissolved gasses to separate out.

During a volcanic eruption, the dissolved gases rush out, carrying the magma with them.

Once the magma reaches the surface and becomes lava, the gases bubble out.

animation of volcano

Dissolved gases

Magma

What are the main parts of a volcano?

Pipe

• A long tube through which magma moves from the magma chamber to Earth’s surface

Vent

The opening through which molten rock and gas leave a volcano

Lava Flow

The area covered by lava as it pours out of a volcano’s vent

Crater

• A bowl-shaped area that forms around a volcano’s central opening

• Lava collects there

Crater

• A bowl-shaped area that forms around a volcano’s central opening

• Lava collects there

Describe the 3 stages of a volcano.

Active (live): volcano that is erupting or has shown signs that it may erupt in the near future.

Dormant (sleeping): volcano that is not currently erupting but may become active in the future.

Extinct (dead): volcano is unlikely to erupt again.

Active: Kilauea

Name: KilaueaLocation: Hawaii

Last eruption: erupting right nowConsidered to be the world’s most active volcano

Active: Eyjafjallajokull

Name: EyjafjallajokullLocation: Iceland

Last eruption: April 14, 2010Caused the shutdown of air traffic across Europe in 2010

Dormant: Fujiyama

Name: Fujiyama (Mount Fuji)Location: Japan

Last eruption: 1708

Dormant: Mount Shasta

Name: Mount ShastaLocation: California, USA

Last eruption: about 1810

Name: Mount KilamanjaroLocation: Tanzania, Africa

Last eruption: 360,000 years ago

Extinct: Kilamanjaro

Name: Olympus MonsLocation: planet Mars

Last eruption: unknown

Extinct: Olympus Mons

Shield Volcano

• A wide, gently-sloping mountain made of layers of lava and formed by quiet eruptions

• Example: The Hawaiian Islands

Cinder Cone• A steep, cone-shaped

hill or mountain made of volcanic ash, cinders, and bombs piled up around a volcano’s opening

• NO SIDE VENTS!

• Example: Sunset crater in Arizona

Composite Volcano

• A tall, cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials

• Example: Mount St. Helens in Washington and Mount Fuji in Japan

Types of Volcanoes (simple version)

• Shield• Stratovolcano• Cinder Cone

Composite Volcano

Relative Size of Volcano Types

Name that Volcano Type!

• Cinder Cone, Mojave Desert, CA

• View of the NNW flank of Mauna Loa Volcano from the south side of Mauna Kea Volcano, Hawai`i; both are shield volcanoes. The largest volcanoes on Earth are shield volcanoes.

• Cinder cone at Little Lake, California.

• Composite • Colima Volcano, Mexico.• A stubby andesite lava flow advances 900-1,200 m down the

southwest side of Colima Volcano. Lava was first observed in the summit crater on November 20 and began spilling over the crater rim the next day. Colima Volcano is the most historically active volcano in Mexico.

• Cinder Cone: (Pu`u ka Pele) was erupted low on the southeast flank of Mauna Kea Volcano. The cone is 95 m in height, and the diameter of the crater at the top is 400 m. Hualalai Volcano in background.

• Composite• Arenal volcano, in Costa Rica

• Shield volcanoes are among the largest on Earth. The island of Hawaii is made of five overlapping shield volcanoes, of which Mauna Kea is the tallest.