Over 300 flights cancelled following series of eruptions on Anak Krakatoa.

Over 300 flights have now been cancelled since Anak Krakatoa, a volcanic island located in the Sunda Strait between Sumatra and Java, began erupting on Friday 4 September 2026. The volcano has produced a series of volcanic columns, some of which have reached over 15 000 m above sealevel. This has led to ash falls across the region, with all flights from Soekarno-Hatta International Airport in Jakarta, which is a little over 100 km to the east of the volcano, being cancelled. The Indonesian Ministry of Health is recommending people avoid going outside without dust masks due to the health hazard presented by the ash, which can cause severe breathing problems, and fishing fleets in the area are reportedly avoiding going to sea because of the poor conditions.

Drone footage of an ash column emerging from Anak Krakatoa on Saturday 5 September 2026. Reuters.

Volcanic ash is extremely hazardous to aircraft in a number of ways. At its most obvious it is opaque, both visually and to radar. Then it is abrasive, ash particles physically scour aircraft, damaging components and frosting windows. However the ash is most dangerous when it is sucked into jet engines, here the high temperatures can melt the tiny silica particles, forming volcanic glass which then clogs engine. When this happens the only hope the aircraft has is to dive sharply, in the hope that cold air passing through the engine during the descent will cause the glass to shatter, allowing the engine to be restarted. Obviously this is a procedure that pilots try to avoid having to perform.

Anak Krakatau is a volcanic island located in the Sunda Strait between Sumatra and Java. The volcano (then known simply as Krakatoa) famously exploded in 1883, killing over 36 000 people (possibly over 120 000), largely through a series of tsunamis. This explosion more-or-less completely destroyed the island, but since then a new volcano, Anak Krakatau (meaning the 'son of Krakatoa'), has grown in its place. Anak Krakatau is almost never completely quiet, but goes through periods of greater and lesser activity. An eruption on 22 December 2018 triggered a tsunami which tsunami caused over 430 fatalities, injured 14 000 people, and displaced 33 000 more along the Sunda Strait. The tsunami risk of this area is particularly high as the coast is very popular with both locals and tourists and is home to over 20 million people within a 100 km distance from the volcano.

Anak Krakatau is located to the north of the Sunda Trench, along which the Australian Plate is being subducted beneath the Sunda Plate, on which the island sits. As the Australian Plate is subducted it is partially melted by the friction and the heat of the planet's interior. Some of this melted material then rises through the overlying Sunda Plate, fuelling Krakatau and the volcanoes of Sumatra and Java.

The Subduction zone beneath Sumatra. NASA/Earth Observatory.

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At least 53 dead following Magnitude 7.7 Earthquake off the coast of Flores Island, Indonesia.

The Indonesian Meteorological, Climatological, and Geophysical Agency recorded a Magnitude 7.7 Earthquake at a depth of about 15 km, to the north of the Island of Flores in East Nusa Tenggara Province, Indonesia slightly before 5.00 am on Saturday 15 August 2026, Eastern Indonesian Time (slightly before 10.00 pm on Friday 14 August, GMT). The Earthquake was felt as far away as Bali, and caused a tsunami as high as 1.6 m on some parts of the coast of Flores. The initial event has been followed by more than three hundred aftershocks.

The approximate location of the 15 August 2026 Flores Earthquake. USGS.

At least 53 people have died as a result of this event, the majority of them killed in their sleep as buildings collapsed onto them, making this the most deadly Earthquake to hit Indonesia since 2022. A further 135 people are known to have been injured, with more than 5000 people displaced and over 1900 homes damaged or destroyed. The Earthquake also caused damage to at least 93 educational facilities, 36 health facilities, 38 government offices, and five places of worship. A maritime passenger terminal collapsed in Maumere on the north coast of Flores.

Damaged and collapsed building in the city of Mbay on the north coast of Flores. Ignasius Kunda/EPA.

Flores is one of the Lesser Sunda Islands, which are located on the northern part of the Timor Microplate. This is trapped between the converging Eurasian and Australian Plates, both of which are being subducted beneath it. In the south the Australian Plate is passing under the island of Timor, while in the north the Eurasian Plate is being subducted in the same way. This is not a smooth process; the rocks of the various plates constantly stick together, only to break apart again as the pressure builds up, causing Earthquakes in the process.

The subduction zones beneath the Timor Microplate. Hamson (2004).

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement. Eventually the pressure builds up too far and the overlying plate snaps back, causing an Earthquake and a tsunami. 

Simplified graphic showing tsunami generation along a convergent margin, and how this can be monitored using ground-based GPS systems to give early warnings of the arrival of tsunamis. NASA/JPL/CalTech.

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Three hikers killed by eruption on Mount Dukono

Three hikers were killed in an eruption on Mount Dukono, a 1273 m high volcano on the northern part of Halmahera Island, Indonesia, on Friday 8 May 2026. The three were part of a group of 20 Indonesian and Singaporean hikers which had trekked up the volcano under the leadership of Indonesian tour guide Reza Selang. The hike was undertaken despite a prohibition on climbing the volcano which had been in place since 17 April, due to a high level of volcanic activity. However, Selang claims he was unaware of this prohibition, and was not made aware of it by local villagers he employs as assistants. Local authorities, meanwhile, claim to have posted warnings on social media and place banners at the entrance to trails leading to the volcano.

An ash column over Mount Dukuno on 8 May 2026. Jhon Frengki Manipa/Reuters.

The group ascended the volcano early in the morning, with Selang sending a drone to the volcano's summit to check for volcanic activity, before sending up a group of fourteen hikers under the leadership of Singaporean tour organiser Timothy Heng, who had booked the trip through Selang last year, while Selang remained lower down with the remainder of the group. At about 7.40 Selang sent his drone up again to check on the group, when the volcano underwent two explosive eruptions in rapid succession, the first producing only smoke, but the second ejecting large volumes of ash, rock, and other debris. 

The group on the mountain scattered and ran downhill in response to this, though Selang reports seeing one man, Singaporean Shahin Muhrez bin Abdul Hamid lying on the ground near the crater. He states that he then ascended the summit along with Heng, who had escaped the initial blast, with the two of them attempting to rescue the injured man. During this attempt both Singaporeans were hit and killed by a large rock, with only Selang escaping.

Selang and the majority of the group made it back to the base of the mountain, where they discovered another person was missing, Indonesian Angel Krishela Pradita. They then notified the local authorities, who sent out a rescue team, who later recovered the bodies of all three missing hikers. The survivors were treated for injuries at a local hospital.

Rescue workers recovering the body of one of the hikers killed on Mount Dukono on 8 May 2026. Badan Nasional Penanggulangan Bencana.

Dukono is one of Indonesia's most active volcanoes, having been erupting more-or-less continuously since 1933. Eruptions most frequently take the form of ash explosions and sulphur dioxide plumes, with lave flows also being reasonably common. The volcano also went a major eruptive phase in the mid sixteenth century, as well as shorter episodes in the eighteenth, nineteenth, and early twentieth centuries.

The Halmahera Islands arc a volcanic arc; formed where one tectonic plate is being subducted beneath another, with the underlying plate being melted by the heat of the Earth's interior, and lighter minerals bubbling up through the overlying plate to form volcanoes. However the Halmahera Islands are unusual in that they lie on a double subduction zone. The underlying plate, a northeaster extension of the Molucca Plate, is being overridden form the Philippine Plate from the east and the Eurasian Plate from the west. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Plate; to the west the Sangihe Islands lie where the Molucca Plate is being overridden by the Eurasian Plate.

Diagrammatic representation of the subduction zones beneath Halmahera (middle), plus the Philippines (top) and Sulawesi (bottom), with the Eurasian Plate to the left, the Molucca Sea Plate in the middle, and the Philippine Plate to the right.  Hall & Wilson (2000).

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Thirty four confirmed dead and many more still missing following landslide in West Java.

Thirty four people have been confirmed dead and 56 are still missing following a landslide which hit the village of Pasirlangu on the side of Mount Burangrang in West Java Province, Indonesia, on Saturday 24 January 2026. As well as local villagers, the landslide is reported to have hit a group of Indonesian marines on a training exercise in the area, who are thought to have been wiped out. So far the bodies of four marines have been recovered, with another nine still missing. 

A rescue team searching the site of a landslide which hit the village of Pasirlangu in West Java on 24 January 2026. Septianjar Muharam/Xinhua.

The landslide is reported to have been triggered by heavy rains associated with the northeast monsoon. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. However, the root cause of the landslide appears to have been deforestation, with a large area of forest above the village cleared to create space for commercial vegetable farming. This process removes the root structure which binds soil together, making slopes more vulnerable to slippage, particularly in areas such as West Java, where soils tend to be volcanic, as such soils typically have much smaller particle sizes and lose cohesion more rapidly when they become waterlogged.

Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry seasons, the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate.

Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

Java has two distinct Monsoon Seasons, with a Northeast Monsoon driven by winds from the South China Sea that lasts from November to February and a Southwest Monsoon driven by winds from the southern Indian Ocean from March to October. Such a double Monsoon Season is common close to the equator, where the Sun is highest overhead around the equinoxes and lowest on the horizons around the solstices, making the solstices the coolest part of the year and the equinoxes the hottest.

The winds that drive the Northeast and Southwest Monsoons in Southeast Asia. Mynewshub.

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Tapanuli Orangutans brought closer to extinction by Cyclone Senyar.

The Tapanuli Orangutan, Pongo tapanuliensis, is thought to have moved significantly closer to extinction after Cyclone Senyar passed across Sumatra on 25 November 2025. The species, which was only discovered in 2017, is considered to be the world's rarest Ape, with a population of about 800 all living within an area of less than 1000 km² in North Sumatra. It is considered to be Critically Endangered under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species.

A male Tapanuli Orangutan, Pongo tapanuliensis. Maxime Aliaga/Sumatran Orangutan Conservation Program.

Cyclone Senyar caused more than 1000 mm of rain to fall in a day in parts of North Sumatra, triggering a series of catastrophic floods and landslides which killed over a thousand people on the island. The three districts where the species is found, North, Central, and South Tapanuli, have been particularly badly hit, with satellite images showing that between 48 and 72 km² of the forest inhabited by Tapanuli Orangutans has been destroyed, according to Erik Meijaard of Borneo Futures, who has been studying the storm's impact on the Apes. This could potentially equate to between 33 and 55 Orangutans, or between 6.2% and 10.5% of the total population.

So far, only a single dead Orangutan has been found, leading to the possibility that the Apes may have been able to escape the area before the worst of the event, although this is not typical Orangutan behaviour; they usually seek the nearest shelter and attempt to wait out large storms. Even should this have been the case, the storm appears to have destroyed large areas of their native habitat, including food sources, which makes it likely that more Orangutans will be lost in the near future. 

A dead Tapanuli Orangutan found amid storm debris in the village of Pulo Pakkat, North Sumatra, following the passage of Cyclone Senyar. Decky Chandra/The Guardian.

The population was already considered to be threatened by the expansion of mining, hydropower projects and palm oil plantations, within their habitat, as well as a rapidly changing environment, with global warning already having led to an increase in rainfall of between 28 and 160% across Sumatra. One possible benefit to the Orangutans is that the Indonesian government has ordered a halt to all new development projects in the Tapanuli area, pending a survey of the region, which may lead to their gaining some extra long-term protection. The government has also indicated its support for forest restoration projects in the region, which could lead to an increase in the available habitat for the Apes.

The storm is also reported to have completely destroyed the Ketambe Research Station, within the Gunung Leuser National Park in Aceh Province, which was the first specialist Orangutan research centre in the world, opened in 1971 by Dutch primatologist Herman Rijksen, and a leading centre for research into the Sumatran Orangutan, Pongo abelii, which is also considered to be Critically Endangered.

Damage caused to the Ketambe Research Station, within the Gunung Leuser National Park by Cyclone Senyar. American Association of Zookeepers. 

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