Formation of Volcanoes

Which of the following most completely defines a volcano?

• a cone-shaped structure on land where pyroclastic material is ejected

• a partly molten region of Earth's mantle where subducting rock is melted

• a ridge system between two diverging plates through which magma escapes

• a vent or hole in Earth's surface through which melted rock or ash erupt

_____ is the thickness of a liquid or its resistance to flow.

• Felsic

• Mafic

• Liquefaction

• Viscosity

When magma has a high viscosity, how is it most likely to erupt?

• quietly

• explosively

• constantly

• most likely will not erupt

Due to it's lower viscosity, which magma type would be the least explosive?

• Felsic

• Mafic

• Ultrafelsic

• Ultramafic

Volcanoes are found along:

• convergent plate boundaries.

• divergent plate boundaries.

• Both A and B

• None of the above

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NGSS.MS-ESS2-3

Volcanoes can form at divergent boundaries when which of the following occurs?

• Plates move toward each other causing the more dense plate to sink and melt, which allows for magma to rise back to the surface.

• Plates move apart from each other allowing for less dense magma to rise up through the fissure.

• Plates move over top a magma plume creating a line of volcanic mountains.

• Plates move side by side, heating the rock and melting it.

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NGSS.MS-ESS2-2

NGSS.MS-ESS2-3

Volcanoes can form at convergent boundaries when which of the following occurs?

• Plates move toward each other causing the more dense plate to sink and melt, which allows for magma to rise back to the surface.

• Plates move apart from each other allowing for less dense magma to rise up through the fissure.

• Plates move over top a magma plume creating a line of volcanic mountains.

• Plates move side by side, heating the rock and melting it.

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NGSS.MS-ESS2-2

Which kind of volcanism is most likely to occur at location A in the following map?

• Location A is a hot spot in oceanic crust, so it is likely to erupt lava with a low silica content, resulting in relatively quiet volcanism.

• Location A is a hot spot in oceanic crust, so it is likely to erupt lava with a high silica content, resulting in explosive volcanism.

• Location A is a mid-ocean ridge at a divergent boundary, so it is likely to erupt lava with a low silica content, resulting in relatively quiet volcanism.

• Location A is a mid-ocean ridge at a divergent boundary, so it is likely to erupt lava with a high silica content, resulting in explosive volcanism.

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NGSS.MS-ESS2-1

A geologist notes that melted rock is escaping from Earth's interior at location A and identifies location A as a volcano. A student objects that location A is too far from any plate boundaries to be a volcano.

Is the student's objection correct? Why?

• Yes; location A is too far from any plate boundaries to be a volcano.

• No; although volcanoes can be located far from plate boundaries, volcanoes erupt lava and ash, not melted rock.

• No; although many volcanoes are located at plate boundaries, volcanoes are also located far from plate boundaries at hot spots.

• No; although volcanoes are located at plate boundaries only, location A is close enough to the boundary between the North American and Pacific plates to be a volcano.

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What process causes the volcanoes of the Hawaiian Islands to form?

• subduction zones

• hotspots

• convergent boundaries

• divergent boundaries