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Types and Processes Gallery - Pyroclastic Cones

Pyroclastic Cones
Pyroclastic cones are the most abundant of volcanic structures. These small cones, named from a combination of the Greek words for fire (pyro) and broken (klastos), are built of fragmental material. They are found both as subsidiary features on larger stratovolcanoes and shield volcanoes or as independent volcanic structures. Pyroclastic cones typically range from a few tens of meters to a few hundred meters in height and are most often formed during single eruptions, when explosively ejected material accumulates around the vent. The slopes of pyroclastic cones consequently approach the angle of repose of its constituent materials. Pyroclastic cones, also known as cinder cones or scoria cones, can form rapidly, but remain active for long periods of time. Parícutin, the famous volcano born in Mexican cornfield in 1943, reached 80% of its 424 m height during its first year, but remained active for 9 years. Tuff cones are a variety of pyroclastic cone formed by more energetic explosions involving groundwater that extensively fragment ejecta, producing finer-grained ash deposits; they typically have steeper slopes and wider craters than cinder cones.

Bora-Bericcio
Mount Bericcio, a rhyolitic pumice cone along the Wonji Fault Belt in Ethiopia, is part of the Bora-Bericcio volcanic complex. Produced by the accumulation of rhyolitic pumice around its vent, Bericcio is capped by a small summit crater. Erosion of the unconsolidated pumice has produced abundant small valleys on the flanks of the cone. Small pumice cones are found on the east flanks of both Bora and Bericcio.

Photo by Giday Wolde-Gabriel, 1984 (Los Alamos National Laboratory).


Kaikohe-Bay of Islands
This basaltic scoria cone is one of 30 Pleistocene to early-Holocene eruptive centers in the Kaikohe-Bay of Islands volcanic field in NW-most North Island, New Zealand. The most recent eruptions produced scoria cones and lava flows near Te Puke about 1,300-1,800 years ago. The volcanic field also contains small shield volcanoes, along with small rhyolitic lava flows and domes.

Photo by Jim Cole (University of Canterbury).


Barren Island
An eruption in 1991 dramatically modified the morphology of the central scoria cone on the small Barren Island, one of the Andaman Islands, north of Sumatra. During the eruption the height of the cinder cone was reduced from 305 to 225 m, and the diameter of its crater increased from 60 to about 200 m. Two small scoria cones also formed in the lava field west of the main cone.

Photo courtesy of D. Haldar, 1992 (Geological Survey of India).


Asosan
Kometsuka scoria cone, on the NW side of the central cone complex of Aso volcano on the island of Kyushu, was constructed about 1,800 years ago. The cone formed during explosive eruptions that were accompanied by lava flows. The Aso caldera walls are visible in the distance.

Copyrighted photo by Dick Stoiber, 1981 (Dartmouth College).


Tolbachik
Lava fountaining at a scoria cone along Kamchatka's Tolbachik S-flank rift zone in late-July 1975. This was the first of three large cones that formed along the northern part of the rift zone during the early stage of the eruption. The lava fountains reached heights up to 1-2.5 km above the vent and ash plumes rose 10-18 km. After 27 July, eruptions from the first cone were dominantly effusive. Activity at the first cone ceased on 9 August.

Photo by Oleg Volynets, 1975 (Institute of Volcanology, Petropavlovsk).


Okmok
A steam-and-gas plume rises in December 1980 from a scoria cone in Alaska's Okmok caldera. Known only as Cone A, it is one of numerous unnamed cones within the 10-km-wide caldera. Erosional furrows produce linear stripes on the flank of the cone. Eruptions in 1945 and 1958 produced lava flows onto the caldera floor. The wall of Okmok caldera forms the skyline ridge.

Photo by Chris Nye, 1980 (Alaska Division of Geological & Geophysical Surveys, Alaska Volcano Observatory).


Bachelor
Kwohl Butte is one in a 25-km-long chain of scoria cones and small shield volcanoes south of Mount Bachelor in the central Cascade Range of Oregon. Despite the youthful appearance of the cone, geologic mapping indicates construction of the chain was completed about 12,000 years ago.

Photo by Lee Siebert, 1981 (Smithsonian Institution).


Newberry
As many as 400 scoria cones that dot the flanks of the massive 30 x 60 km wide Newberry shield volcano in Oregon are seen in this view from Paulina Peak on the south rim of Newberry caldera. The scoria cones at Newberry are most abundant on the north and south flanks. Many are of Pleistocene age, but cones along a rift on the NW flank and some on the south flank have erupted during the Holocene.

Photo by Lee Siebert, 1972 (Smithsonian Institution).


Crater Lake
The Wizard Island scoria cone has a symmetrical 90-m-wide crater at its summit, formed above the west floor of Oregon's Crater Lake caldera within a few hundred years of caldera formation. A lava flow created the peninsula in the foreground on the NW side of the cone, which forms a small island on the west side of Crater Lake.

Photo by Lee Siebert, 1981 (Smithsonian Institution).


Washington
The contrasting morphology of rounded Hayrick Butte on the left and flat-topped Hoodoo Butte on the right, north of Mount Washington in the central Oregon Cascades, reflects dramatic differences in their origin. Hoodoo Butte is a "tuya," a volcanic cone formed by eruptions that ponded in a cavity melted through a glacial ice sheet. Hayrick Butte formed slightly later, when the Pleistocene ice sheet had melted, and formed the classic rounded profile of a scoria cone.

Photo by Lee Siebert, 1995 (Smithsonian Institution).


Pinacate
Cerro Colorado tuff cone is one of the most prominent features of the Pinacate volcanic field in Mexico. This aerial oblique view from the NW shows the 1-km-wide crater with the highest point on the S rim. Tuff beds that compose the S rim dip inward up to 20-25 degrees. Cerro Colorado's crater was formed during several episodes of phreatomagmatic eruptions from multiple vents, during which portions of the tuff cone slumped into the crater.

Photo by David Roddy, 1965 (U.S. Geological Survey).


San Quintín Volcanic Field
The Volcán Sudoeste scoria cone, and smaller cones at its base, are part of the San Quintín volcanic field in México's Baja Peninsula. They are seen here from the north on the slopes of Picacho Vizcaino. Volcán Sudoeste is one of the youngest scoria cones of the field.

Photo by Jim Luhr, 1990 (Smithsonian Institution).


Isla Isabel
A sea-cliff exposure at the southern end of Islota Pelón, located off the NW coast of Isla Isabel, shows a dramatic angular uncomformity between two generations of dipping tuff beds. The large volcanic bomb perched on the rim at the top lies on dipping layers in the interior of the tuff cone. Wave erosion has left only the arcuate western rim of Islota Pelón, whose vent lies out of view to the right.

Photo by Jim Luhr, 1999 (Smithsonian Institution).


Bárcena
An aerial view from the SE shows the Bárcena tuff cone, constructed during an eruption in the Revillagigedo Islands off the western coast of México during 1952-53. The 700-m-wide crater is partially filled by lava, and the lava delta at the lower right was fed from a vent on the flank. The tuff cone was constructed to a height of about 330 m from near sea level within the first few weeks of an eruption that began on 1 August. Lava was seen in the crater by mid-September and flank lava extrusion began on 8 December.

Photo by Adrian Richards, 1955 (U.S. Navy Electronics Laboratory).


Michoacan-Guanajuato
By the end of the 9-year-long eruption of Parícutin, the new scoria cone had risen 424 m above the surface of the original cornfield. The 900-m-wide oval-shaped cone is elongated in a NW-SE direction and is truncated by a circular 280-m-wide crater. The western peak (right) is the highest point on the crater rim. The NE-flank peak of Nuevo Juatita is in the foreground with its top covered by white minerals from fumaroles, and was the main source of lava flows during the last five years of the eruption.

Photo by Jim Luhr, 1997 (Smithsonian Institution).


Cerro Negro
The Cerro Negro scoria cone formed in April 1850. It has been one of Nicaragua's most active volcanoes, building up a roughly 250-m-high cone surrounded by a field of young lava flows. Cerro Negro is seen here in 1981 from Cerro la Mula to the north, the next in a chain of four cinder cones erupted along a N-S line.

Photo by Mike Carr, 1981 (Rutgers University).


Darwin
The tuff cones of Tagus (upper left) and Beagle (lower right) were formed by phreatomagmatic eruptions at Darwin volcano in the Galápagos Islands. The rim of Tagus is breached by Tagus Cove that was visited by Charles Darwin's vessel, the Beagle. Tagus tuff cone has at least four nested craters, the youngest of which contains a small salt lake. Young black lava flows from fissures on the flanks largely surround the tuff cones.

Aerial photo by U.S. Air Force.


Santiago
Cabo Cowan is a tuff cone at the NW tip of Santiago Island in the Galápagos Islands. Wave erosion has truncated the flanks of the cone, forming vertical sea cliffs that expose its interior stratigraphy. The cone is located where the NW-trending rift zone along the crest of Santiago shield volcano encounters the sea.

Photo by Lee Siebert, 1978 (Smithsonian Institution).