, composite cone
, or composite volcano
is a tall conical mountain volcano
composed of both hardened lava
and volcanic ash
. These volcanoes form because the lava that formed them was viscous, and so cooled and hardened before spreading, making the steep mountain. Such lava tends to be high in silica
. At the opposite end of the spectrum are shield volcanoes
, which are formed from less viscous lava, giving them a wide base, and shallow slope.
Because most volcanoes have a stratified (layered) structure, some volcanologists prefer to use the term stratovolcano.