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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Landslide kills at least four on eastern Flores Island, Indonesia.

Four people have been confirmed dead and another four are missing following a landslide at Kampung Culu in Mbeliling District on Flores Island in East Nusa Tenggara Province, Indonesia, which happened overnight between Thursday 7 and Friday 9 March 2019. Rescue teams are still searching for the missing persons, as well as trying to clear debris from a road which it buried, which serves as the main access route between the westernmost portion of Flores and the rest of the island. The incident happened amid heavy rains that have brought flooding to parts of the island. 

The approximate location of the March 2019 Flores landslide. Google Maps.

Flores has a tropical climate, with a Rainy Season related to the Northeast Monsoon that lasts from December to March, with each of those months typically receiving more than 250 mm of rain. Indonesia 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 (this Southern Monsoon does not typically reach Flores, resulting in a dry season over these months). 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.

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 season 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.

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Six people killed by eruption on Mount Rokatenda.

Six people, including two children have been killed by an eruption on Mount Roketenda on the tiny Indonesian island of Palue (or Paluweh), to the north of Flores (East Nusa Tenggara) in the Lesser Sunda Islands. The eruption, which took place at around 4.30 am local time on Saturday 10 August 2013 (around 8.30 pm on Friday 9 August, GMT), producing an ash column 2 km high. All of those killed were on a beach close to the volcano which was hit by a rain of hot ash. The beach had in theory been part of a 3 km exclusion zone around the volcano set up after an eruption in October 2012, but local people had apparently become complacent and begun to re-enter the area (the island is only 4 km across).

The 10 August 2013 eruption on Mount Rokatenda, seen from Maurole on the north coast of Flores. AFP.

Flores (and Paluweh) sits on the northern part of the Timor Microplate; a small fragment of crust caught between the Banda Sea Plate to the north and the Australian plate to the south. Both these other plates are subducting beneath the Timor Plate, and as they sink into the Earth, melted by the friction and the heat of the planets interior. Some of this melted material then rises through the overlying plate, fueling the volcanoes of Flores and Timor.

The approximate location of Palue Island. Google Maps.

See also Earthquake beneath the Banda Sea, Eruption on Mount Paluweh, Eruption on Mount Sirung and Eruptions on Batu Tara.

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Eruption on Mount Paluweh.

Paluweh (or Rokatenda) is an island volcano 10 km off the north coast of Flores Island. It rises 875 m above sea level, or roughly 3000 m above the sea floor, forming a flattened conical island 8 km wide. The volcano is fairly active, having erupted seven times in the twentieth century, although it is likely that other eruptions occurred and were missed, due to the remote nature of the island. The largest recorded eruption occurred in 1928, when an explosive eruption caused a massive landslide, triggering a tsunami that killed 160-300 people.

Paluweh Island. Mangiwau/Flikr.

On 11 to 13 November 2012, the Darwin Volcanic Ash Advisory Centre reported a plume rising 2.4 km above the island which drifted 90-150 km to the northwest. According to the Jakarta Post 196 people have left the island, out of a population of roughly 6000, and 109 of these have needed hospital treatment for respiratory conditions.

Ash column apparently rising from a side vent on Paluweh. Noticieros Televisa.

Flores (and Paluweh) sits on the northern part of the Timor Microplate; a small fragment of crust caught between the Banda Sea Plate to the north and the Australian plate to the south. Both these other plates are subducting beneath the Timor Plate, and as they sink into the Earth, melted by the friction and the heat of the planets interior. Some of this melted material then rises through the overlying plate, fueling the volcanoes of Flores and Timor.

See also Eruption on Mount Sirung, Eruptions on Batu Tara, Fishermen targeting tuna in East Timor at least 42 000 years ago and Volcanoes on Sciency Thoughts YouTube.

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