A caldera is a large cauldron-like hollow that forms following the evacuation of a magma chamber/reservoir. When large volumes of magma are erupted over a short time, structural support for the crust above the magma chamber is lost. The ground surface then collapses downward into the partially emptied magma chamber, leaving a massive depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Only seven known caldera-forming collapses have occurred since the start of the 20th century, most recently at Bárðarbunga volcano in Iceland.
Krakatoa, or Krakatau, is a caldera in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The name is also used for the surrounding volcanic island group comprising four islands: two of which, Lang and Verlaten, are remnants of a previous volcanic edifice destroyed in eruptions long before the famous 1883 eruption; another, Rakata, is the remnant of a much larger island destroyed in the 1883 eruption.
The Special Region of Yogyakarta is a provincial-level autonomous region of Indonesia in the southern Java. It is bordered by the Indian Ocean to the south, as well as sharing all the land borders to the province of Central Java. Ruled by the Yogyakarta Sultanate, the region is the only officially recognised monarchy within the government of Indonesia. The city of Yogyakarta is the capital and the economic center of the region.
Mount Bromo, is an active volcano and part of the Tengger massif, in East Java, Indonesia. At 2,329 meters (7,641 ft) it is not the highest peak of the massif, but is the most well known. The massif area is one of the most visited tourist attractions in East Java, Indonesia. The volcano belongs to the Bromo Tengger Semeru National Park. The name of Bromo derived from Javanese pronunciation of Brahma, the Hindu creator god.
The Bukit Barisan or the Barisan Mountains are a mountain range on the western side of Sumatra, Indonesia, covering nearly 1,700 km (1,050 mi) from the north to the south of the island. The Bukit Barisan range consists primarily of volcanoes shrouded in dense jungle cover, including Sumatran tropical pine forests on the higher slopes. The highest peak of the range is Mount Kerinci at 3,800 metres (12,467 ft). The Bukit Barisan Selatan National Park is situated towards the southern end of the range.
Mount Merapi, Gunung Merapi, is an active stratovolcano located on the border between Central Java and Yogyakarta provinces, Indonesia. It is the most active volcano in Indonesia and has erupted regularly since 1548. It is located approximately 28 kilometres (17 mi) north of Yogyakarta city which has a population of 2.4 million, and thousands of people live on the flanks of the volcano, with villages as high as 1,700 metres (5,600 ft) above sea level.
Mount Agung or Gunung Agung is a volcano in Bali, Indonesia, southeast of Mt Batur volcano, also in Bali. Gunung Agung stratovolcano is the highest point on Bali. It dominates the surrounding area, influencing the climate, especially rainfall patterns. From a distance, the mountain appears to be perfectly conical. From the peak of the mountain, it is possible to see the peak of Mt Rinjani on the nearby island of Lombok, to the east, although both mountains are frequently covered in clouds.
Mount Rinjani or Gunung Rinjani is an active volcano in Indonesia on the island of Lombok. Administratively the mountain is in the Regency of North Lombok, West Nusa Tenggara. It rises to 3,726 metres (12,224 ft), making it the second highest volcano in Indonesia.
The Ijen volcano complex is a group of composite volcanoes located on the border between Banyuwangi Regency and Bondowoso Regency of East Java, Indonesia.
A mud volcano or mud dome is a landform created by the eruption of mud or slurries, water and gases. Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they do not produce lava and are not necessarily driven by magmatic activity. The Earth continuously exudes a mud-like substance, which may sometimes be referred to as a "mud volcano". Mud volcanoes may range in size from merely 1 or 2 meters high and 1 or 2 meters wide, to 700 meters high and 10 kilometers wide. Smaller mud exudations are sometimes referred to as mud-pots.
Kelud is an active stratovolcano located in East Java, Indonesia. Like many Indonesian volcanoes and others on the Pacific Ring of Fire, Kelud is known for large explosive eruptions throughout its history. More than 30 eruptions have occurred since 1000 AD. In 2007, an effusive explosion filled the crater with a lava dome. It last erupted on February 13, 2014, destroying the lava dome and ejecting boulders, stones and ashes up to West Java about 500 kilometers from Mount Kelud. The crater filled with water during the rainy season.
Anak Krakatoa or Anak Krakatau, is an island in a caldera in the Sunda Strait situated between the islands of Java and Sumatra in the Indonesian province of Lampung. On 29 December 1927, Anak Krakatau, or "Child of Krakatoa", emerged from the caldera formed in 1883 by the explosive volcanic eruption which destroyed the island of Krakatoa. There has been sporadic eruptive activity at the site since the late 20th century, culminating with a large underwater collapse of the volcano which caused a deadly tsunami in December 2018. The island is one of several in the area which are of considerable interest to volcanologists, and the subject of extensive study.
Karangetang is a volcano located on the north side of Siau Island off the coast of Sulawesi, Indonesia. The island is inhabited by 22,000 people. It is one of the most active volcanoes in Indonesia having erupted forty-one times since 1675. A pyroclastic flow in 1997 killed three people.
Mount Merbabu is a dormant stratovolcano in Central Java province on the Indonesian island of Java. The name Merbabu could be loosely translated as 'Mountain of Ash' from the Javanese combined words; Meru means "mountain" and awu or abu means "ash".
The Sidoarjo mud flow or Lapindo mud is the result of an erupting mud volcano in the subdistrict of Porong, Sidoarjo in East Java, Indonesia that has been in eruption since May 2006. It is the biggest mud volcano in the world; responsibility for it was credited to the blowout of a natural gas well drilled by PT Lapindo Brantas, although some scientists and company officials contend it was caused by a distant earthquake.
Mount Sinabung is a Pleistocene-to-Holocene stratovolcano of andesite and dacite in the Karo plateau of Karo Regency, North Sumatra, Indonesia, 40 kilometres (25 mi) from the Lake Toba supervolcano. Many old lava flows are on its flanks and the last known eruption, before recent times, occurred in the year 1600. Solfataric activities were last observed at the summit in 1912; recent documented events include an eruption in the early hours of 29 August 2010 and eruptions in September and November 2013, January, February and October 2014. A pyroclastic flow in May 2016 killed seven people. Between 2013 and 2014 the alert for a major event was increased with no significant activity. On 2 June 2015, the alert was again increased, and on 26 June 2015, at least 10,000 people were evacuated, fearing a major eruption. The long eruption of Mount Sinabung is similar to Mount Unzen in Japan, which erupted for five years after lying dormant for 200 years.
Arjuno-Welirang is a stratovolcano in the province of East Java on Java, Indonesia. It is a twin volcano, with the 'twins' being Arjuno and Welirang. There is at least one other stratovolcano in the area, and there are around 10 pyroclastic cones nearby. They are located in a 6 km line between Arjuno and Welirang. The Arjuno-Welirang volcanic complex itself lies in the older two volcanoes, Mount Ringgit to the east and Mount Linting to the south. The summit lacks vegetation. Fumarolic areas with sulfur deposits are found in several locations on Welirang.
