How do composite volcanoes form

The lava that creates shield volcanoes is fluid and flows easily. The spreading lava creates the shield shape. Shield volcanoes are built by many layers over time and the layers are usually of very similar composition. The low viscosity also means that shield eruptions are non-explosive. Cinder cones are the most common type of volcano. A cinder cone has a cone shape, but is much smaller than a composite volcano. Cinder cones rarely reach meters in height but they have steep sides.

Cinder cones grow rapidly, usually from a single eruption cycle Figure below. Cinder cones are composed of small fragments of rock, such as pumice, piled on top of one another. The exact composition of a cinder cone depends on the composition of the lava ejected from the volcano. Cinder cones usually have a crater at the summit. In , a Mexican farmer first witnessed a cinder cone erupting in his field. By , it reached meters and then stopped erupting. Cinder cones are often found near larger volcanoes Figure below.

This Landsat image shows the topography of San Francisco Mountain, an extinct volcano, with many cinder cones near it in northern Arizona. Sunset crater is a cinder cone that erupted about 1, years ago. Supervolcano eruptions are extremely rare in Earth history.

A supervolcano must erupt more than 1, cubic km cubic miles of material, compared with 1. Helens or 25 km 3 for Mount Pinatubo, a large eruption in the Philippines in Not surprisingly, supervolcanoes are the most dangerous type of volcano. Join our community of educators and receive the latest information on National Geographic's resources for you and your students.

Skip to content. Photograph by J. Baylor Roberts, National Geographic. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Mount St. Mount Vesuvius. Also known as a composite volcano. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Media If a media asset is downloadable, a download button appears in the corner of the media viewer.

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Types of Volcanic Cones. View Article. MapMaker: Volcanoes. View Map. These volcanoes usually do not produce streams of lava. In , a farmer in Mexico witnessed the first eruption of a cinder cone in his field Figure 8. By , it grew to a peak of meters tall, and then stopped erupting.

This rapid growth and single eruption cycle is characteristic of cinder cones. For this reason, cinder cones do not reach the sizes of stratovolcanoes or shield volcanoes. The exact composition of a cinder cone depends on the composition of the lava ejected from the Earth. In certain areas of the world, huge calderas have been found to be the remains of volcanic eruptions of enormous scale Figure 8.

These calderas are volcanic features that are formed by the collapse of a huge amount of land due to the powerful eruptions. Caldera comes from Latin word, meaning cauldron. Calderas are generally circular shaped geographic formations like the picture in figure 6.

These are not singular mountains but entire geographical areas. Yellowstone National Park in Wyoming is another caldera that has blown about a hundred times in the last 16 million years.

Supervolcanoes represent the most dangerous type of volcano. An eruption from a supervolcano could change life on Earth as we know it for many years. Supervolcanoes were not even accepted in volcanology until this millennium. Many supervolcano eruptions are thought to have occurred, the most recent in New Zealand less than years ago.

That explosion was thought to have ejected about cubic kilometers of material. A supervolcano eruption near what is now Colorado was thought to have let loose over 5, cubic kilometers of material millions of years ago. In comparison, the Mt. Saint Helens eruption ejected about 1 cubic kilometer of material. The eruptions from supervolcanoes can be so large that the ash ejected into the air blocks the Sun and lowers the temperature on the entire planet. The lowered temperatures caused by these eruptions is called a volcanic winter.

One can only imagine how such a huge eruption would change the world in modern times. The largest supervolcano in North America is the Yellowstone caldera, which had three super eruptions at 2. Long Valley caldera, south of Mono Lake in California, is the second largest supervolcano in North America, erupting extremely hot and explosive rhyolite around , years ago.

An earthquake swarm in alerted geologists to the possibility of another eruption in the future, but the timing of such an event is unknown.