Another type of classical cone-shaped volcano is the stratovolcano.
However, when it comes to size and the ability to pack a serious punch,
stratovolcanoes outclass cinder cones in a big way. In fact, it is
quite common to find much smaller cinder cones adorning the flanks
of these giant mountain-sized volcanoes. A stratovolcano also has
steep sides with a distinguishing cone shape and is frequently composed
of several different vents that erupt lava, sometimes in different
ways.
Pyroclastic flows*,
lava domes**,and cinder cones sometimes characterize stratovolcanoes.
Usually, these types of volcanoes erupt explosively and violently,
sometimes completely blowing their tops!
Some of the most powerful and destructive volcanoes in human history
have been stratovolcanoes. They can send cubic miles of rock and ash
into the atmosphere in an extremely violent series of eruptions known
as a plinian-type eruption. The build up
of extreme - really extreme - pressure beneath the surface from gases
trapped in the magma trying to escape eventually breaks loose in a
violent paroxysm, liberating enormous volumes of overlying rock, steam
and ash into the atmosphere. With some historically famous and cataclysmic
volcanoes, the build up of pressure beneath the crust of the volcano
was so extremely intense that the entire volcanic mountain blew up,
leaving just the root of the original mountain remaining.
Here are some classic examples of these awesome explosions...
Krakatoa
In 1883 this volcanic island in the Sunda Strait experienced
a series of extremely violent eruptions that sent ash over 50 miles
up into the atmosphere and whose explosions could be heard 2,200 miles
away. 36,000 people lost their lives on the nearby islands of Java
and Sumatra when enormous tsunamis generated by the tremendous release
of energy from the eruptions swept over the island. The eruptions
ejected so much material from the interior of the volcano that when
the eruptions were over, there was just a crescent-shaped fragment
of the original island remaining. It completely blew itself up.
Tambora
In 1815 this Indonesian volcano erupted in a series of extremely
violent explosions that are said to be the largest in recorded history.
Ash was thrown 50 km into the atmosphere and global temperatures around
the world fell an average of 3°C. Although it doesn't sound like
much of a drop, in the higher latitudes the effect of the ash in the
atmosphere cooled summer temperatures so much 1815 became known as
the year without a summer.
If the eruptions of a stratovolcano
continue long enough to evacuate enough earth from
beneath the surface, the entire
top of the mountain can completely collapse into the empty chamber
below, leaving a caldera. Although a caldera is usually what happens
after a stratovolcano blows its top or spills all its guts, there
is another insidious and extremely powerful type of volcanic caldera
eruption that truly qualifies as an Extreme Volcano.
