Tephra is the term used to describe the rock ejecta thrown out during a volcanic eruption. This occurs in various sizes, each with its own associated risks.
|
Diameter of Rock Fragments |
Term Used |
|
< 0.2 cm |
ash |
|
0.2 to 6.4 cm |
lapilli |
|
> 6.4 cm (may be meters in diameter and weigh tons) |
blocks or bombs |
Secondary thickening refers to mixtures of ash and water that form aggregates which fall faster and tend to revert to ash on landing.
|
Type of Fragment |
Time Aloft |
Maximum Distance from Volcano |
|
massive blocks |
seconds to minutes |
few kilometers |
|
smaller blocks and bombs |
several minutes |
up to 80 kilometers |
|
large lapilli |
minutes to hours |
hundreds of kilometers |
|
small lapilli |
minutes to hours |
hundreds of kilometers |
|
coarse ash |
hours to days |
thousands of kilometers |
|
very fine ash |
up to 3 years |
global |
|
Type of Fragment |
Hazard |
|
ash |
cause roof collapse, bury, inhalational injury, suffocate, blinding, skin irritation, burns |
|
lapilli |
missile, roof collapse, bury, burns |
|
bomb |
missile, burns |
|
blocks |
crush |
People at risk from breathing very fine ash:
(1) very small children or the elderly
(2) patients with asthma or chronic respiratory diseases
(3) smokers
The presence of quartz or cristobalite in the ash can cause pulmonary silicosis if breathed over an extended period of time.
Specialty: Emergency Medicine, Critical Care
ICD-10: ,
