Some volcanoes have a very simple cone shape. They are built up by just one eruption, or by very few subsequent eruptions. These cones, or domes, are built up over a few weeks or months.
Examples
--Sunset Crater in Arizona
--the small volcanoes of Craters of the Moon National Monument in Idaho
--Chaine des Puys volanic province in central France
At the other extreme, are "complicated" volcanoes - built up by multiple eruptions over long periods of time (thousands or even hundreds of thousands of years.) Phases of lava and pyroclastic accumulation are interspersed with phases of destruction caused by explosive activity, the collapse of a volcano's flanks, or subsidence of basement rock. During these eruptions, and during the intervals between, erosion due to runoff shapes these volcanoes.
Examples
the volcanoes of the San Francisco Peaks
near Flagstaff, Arizona
the volcanoes of the Cascades in the Pacific Northwest
Cantral Volcano in northern France
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Bibliography
Living Mountains, How and Why They Erupt, by Jacques Kornprobst and Christine Laverne
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