Volcanic Processes and Rock Types

The video tutorial explains the differences between magma and lava, highlighting that magma is underground while lava is on the Earth's surface. It introduces extrusive and intrusive igneous rocks, with examples like Pikes Peak and Yosemite. The video also covers factors affecting volcano explosiveness, such as silica and dissolved gases. It discusses the role of dissolved gases and solids in magma, and how cooling rates affect crystal size. Finally, it explains rock composition, focusing on granitic and basaltic rocks, and their impact on density and tectonics.

What is the primary difference between magma and lava?

• Their chemical composition

• Their temperature

• Their location relative to the Earth's surface

• Their color

What are extrusive igneous rocks?

• Rocks formed from magma that cools underground

• Rocks that are only found in oceanic crust

• Rocks formed from lava that cools on the Earth's surface

• Rocks that contain no minerals

Which two factors are crucial for a volcano to be explosive?

• High temperature and low pressure

• Silica content and dissolved gases

• Large magma chamber and high altitude

• Presence of water and carbon dioxide

What role do dissolved gases play in volcanic eruptions?

• They prevent the formation of crystals

• They cool the magma

• They increase the density of the magma

• They build up pressure leading to eruptions

What are volatiles in the context of magma?

• Dissolved gases within the magma

• Solids that form crystals

• Rocks that form on the ocean floor

• Minerals that do not melt

How does the cooling rate of lava affect crystal size?

• Faster cooling results in smaller crystals

• Slower cooling results in smaller crystals

• Cooling rate has no effect on crystal size

• Faster cooling results in larger crystals

What is a characteristic of phaneritic rock texture?

• It has large, visible crystals

• It has no visible crystals

• It contains only small crystals

• It is glassy and smooth

What distinguishes granitic composition from basaltic composition in rocks?

• Basaltic rocks are found only on continents

• Granitic rocks are denser

• Basaltic rocks contain more silica

• Granitic rocks are lighter in color

Why does continental crust float on oceanic crust?

• It is thicker

• It is made of heavier metals

• It is less dense due to high silica content

• It is more flexible

What type of rocks are typically found on volcanic islands like Hawaii?

• Granitic rocks

• Metamorphic rocks

• Sedimentary rocks

• Mafic rocks