Geology 309 - Lecture 7
Basaltic Eruptions - subaerial
I. Fissure eruptions
A. Classic example: Laki fissure eruption 1783
Largest eruption in historical time, 14 cubic km of basalt, 27
km long fissure. Book describes environmental effects in
first part of Chapter 17
II. Hawaiian eruptions
A. Classic example: Hawaii, the big island
B. Definition - weak ejection of very fluid magma as fire fountains from
summit caldera or from fissures on flanks (pulsating).
1. low viscosity, low yield strength (approaching Newtonian).
Exsolving volatiles can vesiculate without violent explosions
2. Basaltic magmas only
3. Deposits - depends on eruption rates. Low, moderate, high eruption
rates will affect whether scoria, spatter, or re-agglutinated lava will
form.
III. Strombolian eruptions
A. Classic example: the Island of Stromboli
B. Definition - intermittent discrete bursts of magma. Higher
viscosity and yield strength than Hawaiian.
1. Mildly explosive eruptions of incandescent pyroclasts to a height of a
few 100' (up to 1000') from summit vent of a
cinder cone and extrusion of lava on flanks
(intermittent). More gas than Hawaiian.
2. Basalt as well as basaltic andesite
3. Can have aa or block lava flows coming out of base of cinder cone
at same time as explosive activity above
Click here
for website with downloadable Strombolian eruption videos shown in class
from the 2000 eruption of Etna
Paricutin
as a classic example.
(Make sure to click on the
Slide show
to see a cool visual of the evolution of the lava flows associated
with Paricutin)
Click here for another link to Paricutin