Mapmaker, National Geographic's classroom GIS tool, features a number of map layers, such as this layer showing Earth's volcanoes.
A volcano is a vent in Earth’s surface from which lava, rock, ash, and hot gases erupt. Most volcanoes are located along the boundaries of tectonic plates, although some, such as those that built the Hawai’ian Islands, are found over hot spots. Scientists suspect that hot spots occur over mantle plumes.
Scientists use a variety of different classification systems to categorize volcanoes for study. This map layer classifies volcanoes as either composite, cinder cone, shield, fissure, caldera, or unknown types. Composite volcanoes, also called stratovolcanoes, are built by two types of eruption; lava flow and pyroclastic flow. Often the eruption begins with an explosion of ash and debris and ends with thick lava flows. The material from these eruptions builds up forming steep slopes with a crater at the top. One of Earth’s most famous volcanoes—Krakatau, located in Indonesia—is classified as a composite volcano.
Cinder cone volcanoes, sometimes called pyroclastic cones, are formed from the build-up of small, loose, pyroclastic debris. Since these hot fragments are small, they cool quickly as they erupt, which prevents them from sticking together. As a result in locations with high winds, the volcanic vent may be located upwind of the cone. An example of this type of volcano is Cerro Negro in Nicaragua.
Shield volcanoes, primarily composed of the igneous rock, basalt, are building over longer periods of time as layer after layer of lava flows and hardens. These appear to be dome-shaped mountains. One example of this type is Mauna Loa, in Hawai’i.
Fissure vents follow the paths of dikes (magma filled fractures in the rock). These dikes may run out the side of another type of volcano or along the ground near a rift zone where two plates are spreading. Iceland has a number of fissure vents as the island sits on two diverging plates, the North American Plate and the Eurasian Plate.
Caldera volcanoes, like Crater Lake in Oregon, United States, are large oval depressions formed by the collapse of the magma chamber after a previous eruption.
The United States Geologic Survey estimates that Earth is home to about 1,500 active volcanoes. Use this layer to explore the awesome force of nature shaping our landscape.
Use this Map Layer in the Classroom
Tectonic Plates and Physical Features: In this activity, students will analyze maps of tectonic plates to predict the location of physical features.
volcano that has had a recorded eruption since the last glacial period, about 10,000 years ago.
type of dark volcanic rock.
large depression resulting from the collapse of the center of a volcano.
hill created by tiny bits of lava blown out of a volcano and fallen down around the volcanic vent. Also called a scoria cone.
steep volcano made of hardened lava, rock, and ash. Also known as a stratovolcano.
bowl-shaped depression formed by a volcanic eruption or impact of a meteorite.
remains of something broken or destroyed; waste, or garbage.
volcano that has erupted in the past but is unlikely to erupt soon.
release of material from an opening in the Earth's crust.
volcano that will no longer erupt.
narrow opening or crack.
intensely hot region deep within the Earth that rises to just underneath the surface. Some hot spots produce volcanoes.
rock formed by the cooling of magma or lava.
molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.
underground reservoir that holds molten rock.
middle layer of the Earth, made of mostly solid rock.
hill created by tiny bits of lava blown out of a volcano and fallen down around the volcanic vent. Also called a cinder cone.
current of volcanic ash, lava, and gas that flows from a volcano.
large, gently sloping volcano made from fluid lava.
steep volcano made of hardened lava, rock, and ash. Also known as a composite volcano.
massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate.
crack in the Earth's crust that spews hot gases and mineral-rich water.
an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.