Cinder cones are considered secondary cones because they generally form in areas of other volcanic activity, including on composite and shield volcanoes. Cinder cones are peaks formed when pyroclastic materials are ejected into the air from a vent and fall back to the ground around the vent in a cone-shaped pile resembling a mound of cinders.
The cones are small, steep-sided, and symmetrical. These volcanoes can form individually over a vent. They can also form in the crater or on the flank of another larger volcano. Wizard Island in Crater Lake National Park in Oregon formed after the summit of Mount Mazama collapsed.
Followings are the steps involved in the formation and growth of a cinder cone.
Vent Formation
Below the ground a magma reservoir forms. It grows in size until the pressure is too great and vents form in the crust. Cinder cones are the most common volcano, and are often found in clusters of up to 100 cones. They can align along fissures, or be parasitic cones on the flanks of a composite or shield volcano.
Cone Formation
Cinder cones typically erupt only once. The magma in the vent contains vesicles (gas bubbles) that cause lava to be thrown up into the air, where it cools and hardens before it falls back to the ground around the vent. These solid lava fragments are called cinders. They pile up in the shape of a cone around the vent.
Lava Flows
Cinder cone eruptions can also include lava flows. Rather than create a conduit through the porous, weak pile of cinders, the lava flows out at the base of the cone, from a vent called a "boca." "Boca" is Spanish for "mouth."
Endangered Volcanoes
Cinder cones can grow to be about 600 to 900 feet tall. The shortest eruptions last less than a month and the longest over 10 years. People mine cinder cones, sometimes destroying them, because the cinders can be used for road construction, road sanding in winters, and decorative "lava rocks" for grills and landscaping. Source: NPS
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