The explosion of a volcanic cone followed by the cone's collapse creates this bowl-shaped crater
The eruption 
and the pyroclastic flow that followed killed 29,000 people almost .... A caldera is 
a large bowl-shaped crater that is formed by the collapse of a volcanic cone after
... [DOC] [TLE] Volcano - The shape of the land, Forces and changes, Spotlight on ... [PAR] Lava (magma that has erupted from a volcano) can create interesting rock ... back 
down to form a cone around a bowl-shaped depression or crater at the summit.