The glacier-capped summit of Ecuador's Cotopaxi volcano is truncated by two nested craters. The outer crater, seen here from the SE, is 800 x 550 m wide. A cone that grew inside this crater is cut by a smaller crater that is 250 m wide and 120 m deep. Frequent explosive eruptions during historical time have modified the shape of the summit crater. In 1903, prior to growth of a broad central cone, it was 450 m deep.
Steam rises from an active fumarolic area on the north side (left center) of the summit lake at Douglas volcano on the northern tip of the Alaska Peninsula. The small, 160-m-wide crater is one of the few ice-free areas on Douglas volcano. In 1992, the lake had a pH of 1.1 and a temperature of 21 degrees Centigrade.
A double crater lake of Kelimutu volcano on Indonesia's Flores Island is seen in this aerial view from the SW. Tiwu Nua Muri Kooh Tai (Lake of Young Men and Maiden) on the left and Tiwu Ata Polo (Bewitched, or Enchanted Lake) are separated by a narrow septum about 35 m high. Phreatic eruptions have occurred from Tiwu Nua Muri Kooh Tai in the 19th and 20th centuries, and continuous upwelling occurs at both lakes.
The northern crater of Ol Doinyo Lengai is seen here in February 1980 from the summit of the volcano. The inner crater is a steep-walled pit that remained after the powerful explosive eruptions of 1966 and 1967. Three years after this photo was taken, another eruption began. Slow lava effusion completely filled in the inner crater. By December 1988, lava had overflowed the near southern crater rim, at the lower center of the photo.
Troitsky crater, the youngest of six craters at the summit of Kamchatka's Maly Semiachik volcano, was formed during a major explosive eruption about 400 years ago. The crater, seen here from the west with the Pacific Ocean in the background, truncates the snow-covered slopes of Ceno-Semiachik, the youngest of the four overlapping stratovolcanoes that comprise the Maly Semiachik massif. The crater, now filled by a hot, acidic lake, has been the source of all historical eruptions from the volcano.
Lake-filled Laguna de Asososca maar, in the foreground, and the conical Cerro Asososca at the upper right were formed by eruptions at the southern end of a N-S fissure system of Las Pilas volcanic complex in Nicaragua. The ages of these vents are not known. This view looks from the NE across the broad plain at the foot of the Marrabios Range to the Pacific Ocean in the distance.
This aerial view on July 1987 looks almost directly down into the double summit crater of Telica volcano in Nicaragua. An older shallower crater is located on the SW side (top). Steam rises from fumaroles in the NE crater (bottom), the source of recent eruptions. The steep-walled crater is 120 m deep. Ash from frequent historical eruptions keeps the outer slopes of the cone unvegetated.
The Mehrener maar is one of about 80 maars of the West Eifel volcanic field. The village of Mehrener is located on the shore of a lake partially filling the crater, whose rim lies behind the village. Maars, scoria cones, and small stratovolcanoes cover an area of 600 sq km west of the Rhine River. Most originated during eruptions between about 730,000 and 10,000 years ago.