Chapter 10 part 2

Volcanic Material

10.1 The Nature of Volcanic Eruptions

◆ Lava Flows

• Basaltic lavas are more fluid.

- Pahoehoe lava (resembles braids in ropes)
- Aa lava (rough, jagged blocks)

• Types of lava

◆ Gases

• One to 5 percent of magma by weight
• Mainly water vapor and carbon dioxide

Pahoehoe (Ropy) Lava Flow

p.282
Figure 2 a

Slow-Moving Aa Flow

p. 282 figure 2 b

Volcanic Material

10.1The Nature of Volcanic Eruptions

• Pyroclastic materials is the name given to

particles produced in volcanic eruptions.

•
The pieces ejected during eruptions range in size

from very fine duct and volcanic ash (less than 2
millimeters) to pieces that weigh several tons.

Volcanic Material

10.1The Nature of Volcanic Eruptions

◆ Pyroclastic Materials

• Types of pyroclastic material

-
-Ash and dust—fine, glassy fragments
- Pumice—frothy, air-filled lava
- Lapilli—walnut-sized particles
- Cinders—pea-sized particles
•

◆ Pyroclastic Materials continued:

Particles larger than lapilli:
Blocks—hardened lava
Bombs—ejected as hot lava

Pyroclastic Flow

Spirit Lake before and after

Lahar

Lahar

A lahar is a violent type of mudflow
or debris flow composed of a slurry
of pyroclastic material, rocky debris
and water. The material flows down
from a volcano, typically along a river
valley.