Section 13-1 Review

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#1Describe three conditions that affect whether magma forms.

Magma forms when . . . • the temperature of the rock rises above the

melting point of the minerals that compose it,

• the pressure of the rock decreases faster than its temperature does,

• when it is mixed with fluids that decrease its melting point.

#2

Explain how magma reaches Earth’s surface.

Magma reaches Earth’s surface because the rising magma is less dense than the surrounding rock of the crust.

#3

Compare magma with lava.

Magma is melted rock beneath Earth’s surface; lava is magma that erupts onto Earth’s surface

Magma Lava

#4

Describe how subduction produces magma.

The denser, subducted plate releases fluids to the surrounding crust and mantle materials, thus lowering their melting points and causing magma to form.

Subduction creating Magma

#5

Identify three tectonic settings where volcanoes commonly occur.

subduction zones

mid-ocean ridges

hot spots

Subduction Zone

Mid-Ocean Ridge

#6

Summarize the formation of hot spots.

The hot spot lies above a column of solid, hot material from the mantle. When the mantle material spreads out at the top of the plume, its pressure drops and the rock melts. The resulting magma forms volcanoes at the hot spot.

Hot Spot

#7

Describe how the presence of ocean water in crustal rocks might affect formation of magma .

Ocean water in ocean rock can lower the melting point of the rock and aid the formation of magma.

#8Yellowstone National Park in Wyoming is far from any plate

boundary. How would you explain the volcanic activity in the park?

The volcanic activity in Yellowstone National Park would be due to mantle plume that cause a hot spot within the continental crust.

Yellowstone Magma Chamber

Yellowstone Volcano History

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