Classifying Volcanoes

What causes a volcano to erupt?

• Pressure builds up in the magma chamber, forcing magma up through the main vent.

• Movement along a fault line opens the crust and forces magma out of the main and side vents

• Convection currents in the mantle push magma out of the vents

Answer explanation

A volcano erupts when pressure builds up in the magma chamber. This pressure forces magma to rise through the main vent, leading to an eruption. The other options do not accurately describe the primary cause of volcanic eruptions.

Volcanoes can be: (Choose 3)

• Dormant

• Closed

• Active

• Extinct

• Open

Answer explanation

Volcanoes can be classified as dormant (inactive but may erupt), active (currently erupting or showing signs of activity), and extinct (no longer capable of erupting). 'Closed' and 'open' are not classifications for volcanoes.

This type of volcano is low to the ground and very wide. Their eruptions involve low viscosity lava that flows for many miles.

• Stratovolcano

• Shield

• Cindercone

Answer explanation

Shield volcanoes are characterized by their low profile and wide base, formed by low viscosity lava that can travel long distances. This matches the description provided in the question.

Type of volcano that is tall and mountainous. It's height is caused by a highly viscous magma that rises and cools before exiting unto Earth's surface. It's also called a composite volcano.

• Stratovolcano

• Shield

• Cindercone

Answer explanation

The correct answer is Stratovolcano, which is characterized by its tall, mountainous structure formed from highly viscous magma. This type of volcano is also known as a composite volcano due to its layered composition.

These volcanoes are usually small and have a large crater. They are made from short-lived eruptions where lava and rock are blown into the air, cool, and fall back down unto the volcano's sides.

• Shield

• Cindercone

• Stratovolcano

Answer explanation

Cindercone volcanoes are characterized by their small size and large craters, formed from explosive eruptions that eject lava and rock, which then cool and accumulate on the slopes, fitting the description provided.

Tags

NGSS.MS-ESS2-1

This volcano is most likely which type of volcano?

• Felsic

• Composite

• Shield

• Cinder cone

Answer explanation

A shield volcano is characterized by its broad, gently sloping sides formed by the eruption of low-viscosity lava. This type of volcano typically produces less explosive eruptions compared to composite or cinder cone volcanoes.

Tags

NGSS.MS-ESS2-2

Name the volcano type pictured:

• cinder cone

• stratovolcano

• shield volcano

• caldera

Answer explanation

The volcano type pictured is a stratovolcano, characterized by its steep, conical shape and layers of lava and ash. This type of volcano typically has explosive eruptions and is commonly found at convergent plate boundaries.

How do changes in a volcano's surface warn of an impending eruption?

• Caving in near the crater shows that magma has moved toward the main vent

• Inflation can show magma close to the surface

• The crater sinking down shows that magma is moving to the side vents

Answer explanation

Inflation indicates that magma is accumulating near the surface, which can signal an impending eruption. This change in the volcano's surface is a key warning sign for monitoring volcanic activity.

Tags

NGSS.MS-ESS3-2

How does seismic activity warn of an eruption? (Choose 2)

• Major earthquakes can trigger an eruption

• Increased minor earthquakes can warn of magma moving beneath the surface

• A sudden decrease in seismic activity can warn of a build up in pressure, meaning an eruption is coming soon

• Afterschocks following a major earthquake can trigger an eruption

Answer explanation

Increased minor earthquakes indicate magma movement, signaling potential eruptions. Conversely, a sudden decrease in seismic activity suggests pressure buildup, which can also precede an eruption.

Tags

NGSS.HS-ESS2-1

NGSS.HS-ESS2-3

What is a steam eruption?

• When gasses such as water, carbon dioxide, and sulfur dioxide are released into the air

• When underwater volcanoes erupt, causing the magma to heat up ocean water

• When magma rises toward the surface, causing the groundwater to boil and releasing steam

Answer explanation

A steam eruption occurs when magma rises toward the surface, heating groundwater to the point of boiling, which then releases steam. This process distinguishes it from other types of eruptions.