A volcanic cone is a triangle-shaped hill formed as material from volcanic eruptions piles up around the volcanic vent, or opening in Earth’s crust. Most volcanic cones have one volcanic crater, or central depression, at the top. They are probably the most familiar type of volcanic mountain. Major Types of Volcanic Cones Composite conesComposite cones are some of the most easily recognizable and imposing volcanic mountains, with sloping peaks rising several thousand meters above the landscape. Also known as stratocones, composite cones are made up of layers of lava, volcanic ash, and fragmented rocks. These layers are built up over time as the volcano erupts through a vent or group of vents at the summit’s crater. The eruptions that form these cones, called Plinian eruptions, are violently explosive and often dangerous. One of the most famous stratocones in the world is Mount Fuji, Japan. The tallest mountain in Japan, Mount Fuji towers 3,776 meters (12,380 feet) above the surrounding landscape. Mount Fuji last erupted in 1707, but is still considered an active volcano. Mount Rainier, Washington, is another stratocone. Mount Rainier rises 4,392 meters (14,410 feet) above sea level. Over the past half million years, Mt. Rainier has produced a series of alternating lava eruptions and debris eruptions. These eruptions have given Mt. Rainier the classic layered structure and sloping shape of a composite cone. Unlike Mount Fuji, Mount Rainier’s composite cone has been carved down by a series of glaciers, giving it a craggy and rugged shape. Cinder conesCinder cones, sometimes called scoria cones or pyroclastic cones, are the most common types of volcanic cones. They form after violent eruptions blow lava fragments into the air, which then solidify and fall as cinders around the volcanic vent. Usually the size of gravel, these cinders are filled with many tiny bubbles trapped in the lava as it solidifies. Cinder cones stand at heights of tens of meters to hundreds of meters. Cinder cones may form by themselves or when new vents open on larger, existing volcanoes. Mauna Kea, a volcano on the American island of Hawaii, and Mount Etna, a volcano on the Italian island of Sicily, are both covered with hundreds of cinder cones. Other Types of Volcanic Cones Spatter ConesVolcanoes often eject small amounts of gaseous lava blobs into the air. These lava blobs, called spatter, are heavy and viscous. Viscosity refers to a substance’s resistance to flow. In this case, it refers to the spatter’s thickness. The viscosity of spatter means it often does not have time to cool before hitting the ground. The lava blobs in spatter stick together as they land, piling up to form steep-sided spatter cones. Most spatter cones are very small, ranging between 1 and 5 meters (3 to 16 feet) in height, because they result from minor volcanic activity. They often form in linear groups along an eruptive fissure, or long crack, on the flank of an active volcano. A small spatter cone is called a hornito. Spatter cones can be found in and around the Puʻu ʻŌʻō region of Mount Kilauea in Hawaii. Continuously erupting since 1983, Kilauea’s volcanic activity is characterized by the fountaining of hot lava, making it the perfect incubator for spatter cones. Tuff ConesUnlike spatter cones that form from lava fountaining, tuff cones form from the interaction between rising magma and bodies of water. Tuff cones are sometimes called ash cones. When heated rapidly by lava, water flashes to steam and expands violently, fragmenting huge amounts of lava into plumes of very fine grains of ash. This ash falls around the volcanic vent, creating an ash cone. Over time, the ash weathers into a rock known as tuff. Tuff cones have steep sides and often stand between 100 and 300 meters (328 to 984 feet) high. They are much wider and have broader craters than spatter cones because they result from shallow explosions that eject materials sideways rather than upwards. Diamond Head, the famous volcano near Honolulu, Hawaii, is an enormous tuff cone. The mountain is the result of a brief volcanic eruption about 200,000 years ago. During Diamond Head’s eruption period, the mountain rose from the ocean, and lava interacted with water and even a nearby coral reef. Today, Diamond Head’s rim is about a kilometer (.62 mile) from the coast, and rises about 232 meters (760 feet) above sea level.