Photos

This true-color image of some of the Indonesian islands is from mid-May 2002. Fire season was not fully underway in the region, and skies over the large island of Borneo (top) were partially cloud-covered, but not hazy with air pollution. The horizontally situated island of Java appears to be experiencing some haze at its western end, and a few scattered fires (red dots) are apparent. Image courtesy of NASA.

The thick brown plume of ash, steam, and volcanic gas rising from Anak Krakatau in this true-color image is a common sight at the volcano. Responsible for one of the largest and most destructive eruptions in Indonesia's history (1883), Krakatau still erupts frequently. For this reason, the volcano is one of 100 that NASA automatically monitors by satellite. Photo courtesy of NASA.

Southeast of the island of Timor (center), a phytoplankton bloom is coloring the waters of the Timor Sea, which separates Timor from northwestern Australia. To the north of Timor is Flores, which is home to numerous active volcanoes. (The red dots are due to fire, not volcanic activity.) The eastern half of Timor, as well as an exclave to the west and a few offshore islands, constitute the country of Timor-Leste. The western portion of Timor and the remaining islands (including Flores) belong to Indonesia. Image courtesy of NASA.

This photograph, taken from the International Space Station in 2015, looks eastward: Java is in the foreground, Bali and Lombok are near the center, and smaller islands trail off toward the horizon. The brightest reflection of the Sun off the sea surface silhouettes Surabaya, Indonesia’s second-largest city of almost 3 million. Against this background of glint as well as regional smoke, a line of volcanoes appears in sharp detail. Volcanoes are the backbone of the islands, which have been formed by the collision of the Australian tectonic plate (right) with the Asian plate (left). The name of each volcano appears in italics. White plumes - each about 80 km (50 mi) long - show that at least six volcanoes appeared to be emitting steam and smoke. The plumes are strikingly parallel, aligned with winds from the northeast. Image courtesy of NASA.

Indonesia is tectonically highly unstable, making it the site of numerous volcanoes and frequent earthquakes. The archipelago lies on the Pacific Ring of Fire where the Indo-Australian Plate and the Pacific Plate are pushed under the Eurasian plate and where they melt at about 100 km (62 mi) below the earths' surface. A string of volcanoes runs southeastward through Sumatra, Java, Bali, and Nusa Tenggara, and then fishhooks north and westward to the Banda Islands of Maluku and North Sulawesi. Indonesia has about 150 active volcanoes, the most of any country on earth. The photo shows a dormant but smoking volcano on the island of Sumatra.

Lake Toba is located in the middle of the northern part of the island of Sumatra, occupying the caldera of a supervolcano. The lake is about 100 km (62 mi) long, 30 km (19 mi) wide, and up to 505 m (1,657 ft) deep. It is the largest lake in Indonesia and the largest volcanic lake in the world. Lake Toba is the site of a supervolcanic eruption estimated at a Volcanic Explosivity Index (VEI) of 8, the largest recorded value on the index. Recent advances in dating methods suggest the date was 74,000 years ago and that it represented a climate-changing event. It is the largest-known explosive eruption on earth in the last 25 million years. Lake Toba was designated a UNESCO Global Geopark in July 2020.

Evidence of tectonic activity. A dormant but smoking volcano on the island of Sumatra.

Inside the caldera of a dormant volcano on the island of Sumatra.

Kuta Beach, Bali.

View from the cliffs at Pura Luhur Uluwatu, Bali.

The Sea Temple of Pura Luhur at Uluwatu in south Bali dates back to the 11th century.

The Sea Temple of Pura Luhur at Uluwatu in south Bali perches on some very impressive cliffs.