Answer:
There are a few historic examples of simultaneous eruptions from
volcanoes or vents located within about 10 km of each other, but
it's very difficult to determine whether one might have caused
the other. To the extent that these erupting volcanoes or vents
have common or overlapping magma reservoirs and hydrothermal
systems, magma rising to erupt from one volcano may effect the
other volcano's "plumbing" system and cause some form of unrest,
including eruptions. For example, the huge explosive eruption of
Novarupta vent in Alaska triggered the summit of nearby Mt.
Katmai volcano to collapse, thereby forming a new caldera (but
no eruption).
For a few of the historic examples of simultaneous eruptions
from nearby volcanoes, scientists actually consider the
individual volcanoes or vents to be part of a larger volcano
complex consisting of overlapping stratovolcanoes, cinder cones,
fissures, vents, and even calderas. In such cases, the erupting
vents (or volcano) are actually part of the same volcano
complex. For example, Tavurvur and Vulcan cones that erupted at
nearly the same time in September 1994 are vents located within
Rabaul
Caldera in
Papua New Guinea. In such cases, one eruption does not really
"trigger" a nearby
vent to erupt; instead, moving magma "leaks" to the surface at
multiple sites.
