Features of Volcanoes
Volcanic Landforms
- Ash and cinder cone:
- An ash and cinder cone is a concave cone, seldom more than 300 m (1,000 ft.) high. It occurs where an explosive eruption ejects fragments from a central crater. Examples can be seen in Idaho, US.
- Composite cone:
- A composite cone, with concave, cone-shaped sides, has alternate ash and lava layers. Fujiyama, in Japan, is an example. If the main pipe has been plugged, gases may blow the top off and the summit may collapse. Crater Lake, in Oregon, US, is an example of the resulting caldera.
- Lava cone:
- A lava cone usually forms from slowly upwelling lava. A steep-sided volcano, like Puy de Dôme in France, grew from sticky acid lava that soon hardened. A shield volcano, like Mauna Loa in Hawaii, US, formed from runny lava that flowed far before it hardened.
- Lava plain (plateau basalt):
- A lava plain occurs where fissures have leaked successive flows of basic lava that have blanketed huge areas of basalt. The Deccan Plateau, in India, is an example.
Emissions from Vents
- Fumarole:
- A fumarole is a small vent emitting jets of steam. Fumaroles can be seen in Alaska, US, Sicily.
- Geyser:
- A geyser is a periodic fountain of steam and hot water forced up by water superheated deep down. Geysers can be seen in Wyoming, US, and Iceland.
- Hot spring:
- A hot spring is heated by hot rocks underground. It releases dissolved minerals, producing crusts of calcium carbonate or quartz. Hot springs can be seen in Iceland and New Zealand.
- Mofette:
- A mofette is a small vent emitting carbon dioxide and other gases. Mofettes can be seen in France and Java.
- Mud cone:
- A mud cone is a low cone deposited by mud-rich escaping water. These cones can be seen in New Zealand and Sicily.
- Smoker:
- A smoker is a submarine hot spring at an oceanic spreading ridge. An example is in the Galápagos Ridge.
- Solfatara:
- A solfatara is a vent emitting steam and sulfurous gas. An example ccan be seen in Italy.
