Volcanoes and Eruptions Quiz

What type of volcano is characterized by steep slopes and explosive eruptions?

• Shield volcano

• Cinder cone volcano

• Composite volcano

• Lava dome

Answer explanation

Composite volcanoes have steep slopes due to their layered structure of lava and ash. They are known for explosive eruptions, making them distinct from shield and cinder cone volcanoes, which have different shapes and eruption styles.

Which type of volcano has a broad base and gentle slopes, with eruptions that primarily produce lava flows?

• Composite volcano

• Shield volcano

• Cinder cone volcano

• Lava dome

Answer explanation

A shield volcano has a broad base and gentle slopes, formed primarily by the flow of low-viscosity lava. This results in eruptions that produce extensive lava flows, distinguishing it from other types of volcanoes.

A volcano produces thin, fluid lava that travels long distances and creates a broad, low-lying structure. What type of volcano is this, and what can you infer about the magma's viscosity?

• Composite volcano; low viscosity

• Shield volcano; low viscosity

• Cinder cone volcano; high viscosity

• Lava dome; high viscosity

Answer explanation

The volcano described is a shield volcano, known for its broad, low profile and fluid lava that can travel long distances. This indicates that the magma has low viscosity, allowing it to flow easily.

A small volcano forms quickly after a single eruption and is made up of fragments of solidified lava. What can you deduce about its eruption style and longevity?

• The eruption was explosive, and the volcano is likely short-lived.

• The eruption was gentle, and the volcano will last for thousands of years.

• The eruption was continuous, and the volcano is stable over time.

• The eruption was fluid, and the volcano will grow larger over time.

Answer explanation

The small volcano formed quickly from solidified lava fragments indicates an explosive eruption style, which typically produces such debris. This suggests the volcano is likely short-lived, as explosive eruptions often do not sustain long-term activity.

A Plinian eruption is best described as:

• A quiet eruption with fluid lava flows

• An explosive eruption with towering ash columns

• A small, localized eruption with minor ash ejection

• A submarine eruption beneath the ocean

Answer explanation

A Plinian eruption is characterized by its explosive nature, producing towering columns of ash and gas. This distinguishes it from quiet eruptions with fluid lava flows or smaller eruptions with minor ash ejection.

Which eruption type involves a short, explosive burst of ash and rock, often forming pyroclastic flows?

• Strombolian

• Hawaiian

• Vulcanian

• Subglacial

Answer explanation

Vulcanian eruptions are characterized by short, explosive bursts of ash and rock, which can lead to the formation of pyroclastic flows. This distinguishes them from other types like Strombolian and Hawaiian eruptions.

A volcanic eruption occurs where magma interacts with seawater, producing explosive steam and lava fragments. What type of eruption is this, and what hazards might it pose?

• Plinian; widespread ashfall

• Phreatic; localized damage

• Surtseyan; explosive steam and ash clouds

• Strombolian; minor lava flows

Answer explanation

The eruption described is phreatic, as it involves magma interacting with seawater, creating explosive steam. This type of eruption can cause localized damage due to steam explosions and the ejection of volcanic material.

During an eruption, magma with low gas content and low viscosity produces continuous lava fountains and flows. Which eruption type does this describe, and what can you infer about the type of volcano formed?

• Hawaiian; shield volcano

• Plinian; composite volcano

• Vulcanian; cinder cone volcano

• Phreatic; lava dome

Answer explanation

The description of low gas content and low viscosity magma producing continuous lava fountains and flows is characteristic of Hawaiian eruptions, which typically form shield volcanoes due to their broad, gentle slopes.

Which type of magma has the highest silica content, making it the most viscous?

• Basaltic

• Andesitic

• Rhyolitic

• Mafic

Answer explanation

Rhyolitic magma has the highest silica content, which increases its viscosity. In contrast, basaltic and andesitic magmas have lower silica levels, making them less viscous. Therefore, rhyolitic magma is the most viscous.

Basaltic magma is commonly associated with:

• Explosive eruptions

• Quiet, fluid lava flows

• High viscosity

• High silica content

Answer explanation

Basaltic magma is typically low in viscosity and has a low silica content, allowing it to flow easily. This results in quiet, fluid lava flows rather than explosive eruptions.