Page 8 - Curriculum Visions Dynamic Book. To close the book, close the tab.

Central vent volcano
 Caldera—A caldera is a large sunken area at the top of a volcano. It is not just a large vent, but the collapsed top of the volcano. The diagrams illustrate the formation of Crater Lake, Oregon, shown in the photograph below.
1—The volcano erupts violently, so that the rocks are weakened. At the same time, the lava pours out of the vent so fast that the magma chamber is left partly empty.
countryside. As a result, the magma chamber is partly empty. Normally, the magma chamber would be slowly filled from below. However, if the magma chamber is close
to the ground surface, the volcano large and heavy, and the rocks above weak, then the weight of
the volcano might be enough to cause the whole top of the cone to collapse down into the partly empty chamber before it can refill.
Many volcanoes remain active even after a catastrophic event like
the collapse of their cones. In time a new cone will grow from the center of the caldera.
Well-developed calderas include the summit area of Vesuvius in Italy. One of the most famous calderas containing a lake is Crater Lake in Oregon. The rim of the crater is 11km across,
42km around, and is partly filled with a lake nearly 600m deep.
The lake contains an island, Wizard Island, which is the tip
of the new cone that is growing from the lake floor to replace the cone that collapsed about 5,000 years ago. Although it looks small, the new cone is 826m high;
the lower 600m are submerged in the lake. The lake and surrounding area make up Crater Lake National Park.
To the northeast lies Yellowstone National Park, with its famous geysers. These geysers have formed on the floor of another caldera. Geysers are common here because the rock was severely fractured during the formation of the caldera, allowing rain and snow to seep down to the hot rocks above the magma chamber.
Central vent volcano
A steep-sided volcano, usually formed into a cone and made of both lava and ash. It is fed by
a single vertical pipe, or vent. Alternative terms are composite volcano and stratovolcano.
2—The weight of the volcano’s cone causes it to collapse in on the magma chamber, producing a vast pit that can, over the following centuries, fill with water.
8