The opening at the top of a volcano is sometimes called the throat of a volcano. Tuff is pyroclastic debris that has been cemented together to form rock. A vent is an opening of a volcano through which debris, gas, and steam flow. The tube or passageway the magma travels on its way from the magma chamber to the opening of a volcano is also called a vent. A volcano is any opening through which melted rock, ash, gas, steam, and small pieces of rock flow.
Volcanology is the study of volcanoes.
The USGS is the United States Geological Survey. The CVO is the Cascades Volcano Observatory. The HVO is the Hawaiian Volcano Observatory. American Geological Institute.