Volcanic Vents

erupting lava
Erupting vents on Mauna Loa during the 1984 eruption. Hawaii Volcanoes National Park, Hawaii.

NPS photo.


A volcanic vent is the place at the Earth’s surface where lava flows, tephra (pyroclastic materials consisting of volcanic ash, lapilli, or bombs), and fragmented rocks are erupted. Volcanic gases are also emitted at vents.

Volcanic vents may be located:

  • In summit craters,

  • On a volcano’s flanks,

  • At the base of a cinder cone,

  • Around the margins of a caldera.

Lake Clark National Park & Preserve

summit crater vent with steam column
Redoubt Volcano (1989). Lake Clark National Park & Preserve, Alaska.

USGS photo by W. White.

Low-level steam and ash eruption from the vent in Redoubt Volcano’s summit crater. Photo taken December 18, 1989.

Craters Of The Moon National Monument & Preserve

flat topped cinder cone flat topped cinder cone

Left image
Watchman cinder cone in Craters of the Moon National Monument & Preserve, Idaho.
Credit: NPS photo from Niles et al. (2011).

Right image
Watchman cinder cone photo with feature labels.
Credit: NPS photo from Niles et al. (2011).

The vent shown above is on the south flank of the Watchman cinder cone in Craters of the Moon National Monument. The lava flowed in a small channel with small spatter ramparts on either side.

Crater Lake National Park

diagram of circular caldera features with arrows indicating outward flow of pyroclastics
Illustration of ring-vents for a caldera eruption on Mount Mazama. Crater Lake National Park, Oregon.

Adapted from from
Bacon, C.R., and Wright, H.M., 2017, Geologic field trip guide to Mount Mazama and Crater Lake Caldera, Oregon: U.S. Geological Survey Scientific Investigations Report 2017–5022–J1 (47 p).

The climatic eruption of Mount Mazama that formed the Crater Lake caldera took place from ring-vents. Arrows show direction of movement of pyroclastic flows. These vents are underneath the lake because landslides that occurred soon after the eruption widened the caldera.

Linear Vents

aerial view linear volcanic vent

Many vents are roughly circular, but other vents may be elongate or linear.

Image (right): Linear fissure vent that was active during the May 2018 eruption of Kīlauea in Hawai‘i Volcanoes National Park, Hawai‘i. This vent is not located within the park's boundary.

Photographer: USGS Hawaiian Volcano Observatory, public domain.

Vent Plugs

lava dome vent plug
Novarupta dome, June 2006.

USGS photo by Pavel Izbekov.

Vents are typically filled with a plug of solidified magma at the end of an eruption. The Novarupta Dome formed at the end of the 1912 eruption in Katmai National Park that created the Valley of Ten Thousand Smokes.

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Part of a series of articles titled Volcanic Features.

Previous: Volcanic Craters

Next: Crater Lakes

Crater Lake National Park, Craters Of The Moon National Monument & Preserve, Hawaiʻi Volcanoes National Park, Katmai National Park & Preserve, Lake Clark National Park & Preserve

Last updated: April 18, 2023