Factoid
Galán is a caldera in Catamarca
Province, Argentina, considered
to be the best exposed large
caldera in the world. It was
formed 2.2 million years ago
when 1,050 km3 of material was
erupted, producing ignimbrite
deposits stretching up to 100 km
away. The caldera was originally
the site of a large lake, but
resurgence of the eastern caldera
floor has confined the salty
Laguna Diamante to the caldera's
western edge.
What is a caldera?
A caldera is a cauldron-like
volcanic feature on large central
volcanoes, a special sort of
volcanic crater (from one to
several kilometers in diameter),
formed when a magma chamber
was emptied. The depression
then originated either in very big
explosive eruptions or in erosion
and collapse of the magma
chamber roof. The previous
emptying of this magma chamber
is often accomplished during a
series of effusive eruptions in the
volcanic system, even kilometers
away from the magma chamber
itself.