Geology Exam 2

What is basement rock made of?

Both igneous and metamorphic rock.

What lies above basement rock?

Sedimentary cover.

What are the building blocks of all rocks?

Minerals.

What do geologists call rocks or melts with high silica content?

Felsic.

What do geologists call rocks or melts with low silica content?

Mafic.

How did vesicles form in igneous rock?

Trapped volcanic gases.

True or false: Gases trapped in magma make eruptions less dangerous.

False.

How do geologists use Bowen’s Reaction Series?

To determine the order of mineral crystallization.

What is the first mineral to crystallize in Bowen’s Reaction Series?

Olivine.

True or false: Sills intrude vertically through the host rock.

False. Sills run parallel to existing rock layers.

True or false: Dikes intrude horizontally through the host rock.

False. Dikes cut across existing rock layers.

True or false: A pluton is a large, amorphous body of igneous intrusion.

True.

What are the five mineral criteria listed in the review?

Naturally occurring, formed by geologic processes, crystalline structure, solid state, definable chemical composition.

What mineral class does a rock picked up outside most likely belong to?

Silicate.

True or false: The silicate tetrahedron is the fundamental building block of silicate minerals.

True.

What is fractional crystallization?

Minerals crystallize out of a melt during cooling, changing the remaining melt’s composition.

How did a porphyritic igneous rock form?

It cooled slowly, then quickly.

What is a coherent, naturally occurring solid aggregate of minerals or glass called?

A rock.

What are three ways to melt rock?

Decrease pressure, add heat, add volatiles such as water.

Why does water move the solidus line in a subduction zone?

Water lowers the melting temperature of mantle rock.

What type of volcano has broad, gently sloping sides and fluid lava?

Shield volcano.

What type of volcano has steep sides and alternating layers of lava and pyroclastic debris?

Stratovolcano (composite volcano).

What type of volcano is a small, steep-sided cone made from loose volcanic fragments?

Cinder cone.

According to the review, pyroclastic debris are more what than lava flows?

More felsic.

True or false: Magma is found on Earth’s surface.

False. Molten rock at the surface is called lava.

True or false: Lava is found on Earth’s surface.

True.

What three things are needed for diamond formation?

Carbon, high temperatures, and high pressure.

What process allows carbon to experience the pressure and temperature needed for diamond formation?

Plate tectonics.

What two factors determine melt viscosity?

Silica content and temperature.

What two properties characterize a low-viscosity melt?

High temperature and low silica.

If a mafic igneous rock melts entirel