Cinder cones are cone-shaped volcanic hills made of loose cinders and other tephra.
Unlike the violently explosive eruptions that create large stratovolcanoes, cinder cones form when runny (low viscosity) lava with lots of gas erupts as liquid fountains. Lava may be spewed hundreds of feet through the air. The molten rock solidifies instantly, often preserving bubbles created by escaping gasses.
If an eruption of this type continues long enough, fragments accumulate layer by layer to form a cinder cone. Cinder cones can grow up to 700 meters (2,300 feet) high, but most are between 30 and 300 meters (100 and 1,000 ft).
Learn more about cinder cones at the USGS Volcano Hazards website or
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