Chapter 18: Volcanic Activity

Question 1

Viscosity

Answer 1

Physical property that describes a material’s resistance to flow

Question 2

Pluton

Answer 2

Intrusive igneous rock bodies; exposed at Earth’s surface as a result of uplift and erosion

Question 3

Batholith

Answer 3

Largest plutons; irregularly shaped masses of coarse-grained igneous rocks that cover at least 100 square kilometers and take millions of years to form

Question 4

Stock

Answer 4

Irregularly shaped plutons that are similar to batholiths but smaller

Question 5

Laccolith

Answer 5

Lens-shaped pluton with a round top and flat bottom

Question 6

Sill

Answer 6

Forms when magma intrudes parallel to layers of rock; range from a few centimeters to hundreds of meters in thickness

Question 7

Dike

Answer 7

A pluton that cuts across the preexisting rocks

Question 8

Vent

Answer 8

Opening at the top of the volcano

Question 9

Crater

Answer 9

At the top of the volcano, around the vent, a bowl-shaped depression

Question 10

Caldera

Answer 10

Larger depressions up to 50km in diameter, often form after the magma chamber beneath a volcano empties from a major eruption

Question 11

Shield Volcano

Answer 11

A mountain with broad, gently sloping sides and a nearly circular base

Question 12

Cinder-Cone Volcano

Answer 12

When eruptions eject small pieces of magma into the air; form as this material (tephra) falls back to Earth and piles up around the vent

Question 13

Tephra

Answer 13

Erupted materials; classified by size

Question 14

Pyroclastic Flow

Answer 14

Rapidly moving clouds of tephra mixed with hot, suffocating gases

Question 15

Hot Spot

Answer 15

Unusually hot regions of Earth’s mantle where high temperature plumes of magma rise to the surface

Question 16

Composite Volcano

Answer 16

Formed of layers of hardened chunks of lava from violent eruptions alternating with layers of lava that oozed downslope before solidifying. Cone-shaped, concave slopes, larger than cinder cones very explosive and dangerous