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.

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

Barren Island

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

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

Aso

Kometsuka scoria cone, on the NW side of the central cone complex of Aso volcano on the island of Kyushu, was constructed about 1800 years ago. Explosive eruptions building the cinder cone were accompanied by lava flows that traveled down the flank of this complex of stratovolcanoes in the center of Aso caldera. A broad moat separates the central cone complex from the caldera walls, which form the horizon.

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

Tolbachik

Powerful jets of incandescent lava rise above the crater of a cinder cone along Kamchatka's Tolbachik south-flank rift zone in late-July 1975. This cinder cone, the first of three large cones formed along the northern part of the rift zone during the early stage of the eruption, began to grow on July 6. At times, powerful lava fountains rose 1-2.5 km above the vent and ash columns reached 10-18 km heights. After July 27, eruptions from the first cone became dominantly effusive. Activity at the first cone ceased on August 9.

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

Okmok

Steam rises in December 1980 from a cinder cone in Alaska's Okmok caldera. Known only as Cone A, it is one of numerous unnamed pyroclastic cones within the 10-km-wide caldera. Erosional furrows produce linear stripes on the flank of the cone. Eruptions from Cone A in 1945 and 1958 produced lava flows, which issued onto the caldera floor. Cone A erupted again six months after the date of this photo. The wall of Okmok caldera forms the skyline ridge.

Photo by Lee Siebert, 1981 (Smithsonian Institution).

Bachelor

Kwohl Butte cinder cone is one in a 25-km-long chain of cinder 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, 1972 (Smithsonian Institution).

Newberry

Some the more than 400 cinder 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 cinder cones at Newberry are most abundant on the north and south flanks. Many are of Pleistocene age, but cinder cones along a rift on the NW flank and some on the south flank have erupted during the Holocene.

Photo by Lee Siebert, 1981 (Smithsonian Institution).

Crater Lake

Wizard Island cinder cone, with 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. A submerged dome, 30 m beneath the surface 1 km east of Wizard Island, is the youngest feature of Crater Lake caldera.

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

Pinacate

Cerro Colorado tuff cone is one of the most prominent features of the Pinacate volcanic field. This aerial oblique view from the NW shows the 1-km-wide crater with its high point on the south rim. Tuff beds at Cerro Colorado dip inward up to 20-25 degrees at the south rim, much more steeply than at the low-rimmed Cráter Elegante. 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 Jim Luhr, 1990 (Smithsonian Institution).

San Quintin

The Volcán Sudoeste cinder 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 San Quintín volcanic field. It lies on a narrow peninsula between the Falsa bay (left) and the Pacific Ocean (right).

Photo by Jim Luhr, 1999 (Smithsonian Institution).

Isabel-Isla

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 tuff beds 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 Adrian Richards, 1955 (U.S. Navy Electronics Laboratory).

Barcena

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 small lava domes, and a fissure on the flank of the cone fed the black lava delta at the lower right. 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 August 1. The first lava dome had formed by mid-September, and flank lava effusion began on December 8.

Photo by Jim Luhr, 1997 (Smithsonian Institution).

Michoacan-Guanajuato

At the end of the 9-year-long eruption of Parícutin, the new cinder cone rose 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 in the foreground, its top covered by white fumarolic sublimate minerals, was the main source of lava flows during the last five years of the eruption.

Photo by Mike Carr, 1981 (Rutgers University).

Cerro Negro

Cerro Negro cinder cone in Nicaragua, Central America's youngest volcano, was born in April 1850. It has been one of Nicaragua's most active volcanoes, building up a roughly 250-m-high cinder cone surrounded by a field of fresh lava flows. Cerro Negro is seen here in 1981 from Cerro la Mula on the north, the next in a chain of four cinder cones erupted along a N-S line.

Aerial photo by U.S. Air Force.

Darwin

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

Photo by Lee Siebert, 1978 (Smithsonian Institution).

Santiago

Cabo Cowan is a tuff cone at the NW tip of Santiago Island in the Galápagos Islands. Its summit crater is breached to the SW, where wave erosion has truncated the flanks of the cone, forming vertical sea cliffs that expose its interior. The 284-m-high tuff cone was constructed by submarine eruptions where the NW-trending rift zone along the crest of Santiago shield volcano encounters the sea.