Understanding Volcanoes

What is a volcano?

• A volcano is an opening in the Earth's crust that allows molten rock, ash, and gases to escape.

• A volcano is a geological formation that traps air and water.

• A volcano is a type of mountain that only erupts once.

• A volcano is a large body of water formed by tectonic activity.

Answer explanation

A volcano is correctly defined as an opening in the Earth's crust that allows molten rock, ash, and gases to escape. The other options incorrectly describe geological features or processes.

What are the three classifications of volcanoes?

• Shield, Composite, Cinder Cone

• Volcanic, Seismic, Tectonic

• Active, Dormant, Extinct

• Lava, Ash, Gas

Answer explanation

Volcanoes are classified based on their activity levels: Active (erupting or likely to erupt), Dormant (inactive but could erupt), and Extinct (no longer erupting). This classification helps in understanding volcanic behavior.

What is the difference between magma and lava?

• Magma and lava are the same substance regardless of their location.

• Magma is always found on the surface; lava is found underground.

• Magma is underground molten rock; lava is magma that has erupted to the surface.

• Lava is a type of rock that forms only in volcanoes; magma does not.

Answer explanation

Magma is molten rock found underground, while lava is the same substance that has erupted to the surface. This distinction is crucial in understanding volcanic processes.

What happens inside a magma chamber?

• Magma accumulates, undergoes crystallization, and may lead to volcanic eruptions.

• Magma is expelled directly into the atmosphere without any buildup.

• Magma chambers are filled with water instead of molten rock.

• Magma cools and solidifies completely without any movement.

Answer explanation

Inside a magma chamber, magma accumulates and can undergo crystallization. This process can build pressure and potentially lead to volcanic eruptions, making this the correct choice.

What can cause a volcanic eruption?

• High temperatures melting ice caps

• Movement of tectonic plates and buildup of pressure in magma.

• Heavy rainfall causing landslides

• Earthquake vibrations disrupting soil

Answer explanation

Volcanic eruptions are primarily caused by the movement of tectonic plates, which leads to the buildup of pressure in magma beneath the Earth's surface. This pressure eventually results in an eruption.

What are the two types of volcanic eruptions?

• Explosive eruptions and effusive eruptions

• Lava flows and gas emissions

• Submarine eruptions and phreatomagmatic eruptions

• Shield eruptions and volcanic domes

Answer explanation

The two main types of volcanic eruptions are explosive eruptions, which involve violent explosions and ejection of materials, and effusive eruptions, characterized by the steady flow of lava. This makes the first choice correct.

What is the main reason why volcanoes form hills or mountains?

• The magma chamber expands pushing the land upwards

• Layers of rock and ash build up from repeated eruptions

• The volcanic vents on the sides push the land upwards

• The lava flow creates a mound of hardened rock

Answer explanation

Volcanoes form hills or mountains primarily because layers of rock and ash accumulate from repeated eruptions. Each eruption deposits materials that build up over time, creating the characteristic shape of a volcano.

What is the main factor that determines the shape of a volcano?

• The location of the volcano (on land or under water)

• The type of rock and minerals in the surrounding crust

• The rate and intensity of the volcanic eruptions

• The size and depth of the magma chamber

Answer explanation

The shape of a volcano is primarily influenced by the rate and intensity of eruptions. High-intensity eruptions typically create steep, conical shapes, while low-intensity eruptions lead to broader, shield-like formations.