How Magma Designs a Volcano (Shape and Composition)

What is the primary factor that determines whether magma is runny or sticky?

• Temperature

• Pressure

• Silica content

• Water content

What type of volcanic eruption is typically associated with high silica magma?

• Gentle eruptions

• Effusive eruptions

• Explosive eruptions

• Submarine eruptions

Which rock type is formed from low-silica magma and is typically dark in color?

• Rhyolite

• Andesite

• Basalt

• Granite

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What type of volcano is characterized by broad, gently sloping sides, formed from low silica magma?

• Stratovolcano

• Cinder cone

• Shield volcano

• Lava dome

What is a characteristic eruption style of shield volcanoes?

• Highly explosive, blasting ash and rock.

• Slow, steady, and calm effusive eruptions.

• Rapid formation with multiple vents.

• Primarily forms rhyolite rock.

Which of the following best describes a composite volcano?

• Small, steep, short-lived, formed from a single burst of activity.

• Large, with gentle slopes, built by calm, effusive eruptions of mafic magma.

• Tall, steep, symmetrical, formed by layering intermediate to felsic magma.

• Characterized by mafic and gas-rich magma that blasts into the air.

How are cinder cone volcanoes primarily formed?

• Through repeated explosive eruptions of viscous, felsic magma.

• By the slow, steady accumulation of runny, mafic lava flows.

• From a single burst of activity where mafic, gas-rich magma blasts into the air and falls as cinders.

• By layering both effusive and explosive materials over hundreds of thousands of years.

How does high silica content affect magma and its eruption style?

• It makes the magma mafic, runny, and leads to effusive eruptions.

• It makes the magma felsic, viscous, and leads to explosive eruptions.

• It causes the magma to be gas-rich, forming simple, steep piles of rock.

• It results in basalt rock type and calm, steady building of wide volcanoes.