The Deadly Landslides Triggered by Cyclone Maila in Papua New Guinea: Key Questions Answered

In April 2026, Tropical Cyclone Maila brought unprecedented rainfall to Papua New Guinea, triggering devastating landslides in East New Britain. The event was unusual because the nation typically faces low cyclone risk due to its equatorial location. But warm ocean waters and favorable atmospheric conditions allowed Maila to strengthen and linger, saturating steep terrain and causing multiple deaths. Satellite imagery from NASA's Landsat 9 captured the stark contrast between lush forests before and after the landslides. Below, we explore the science behind this disaster through frequently asked questions.

What made Tropical Cyclone Maila so destructive in Papua New Guinea?

Cyclone Maila's destructiveness stemmed from a combination of high intensity and unusually slow movement. It reached Category 4 strength on Australia's cyclone scale (equivalent to Category 3 on the U.S. Saffir-Simpson scale), packing powerful winds and torrential rain. More critically, instead of sweeping past quickly, Maila lingered near the islands of Bougainville, New Britain, and New Ireland for an extended period. This allowed its rainbands to repeatedly strike the same areas, particularly East New Britain. The prolonged downpour saturated the soil on steep slopes in the Gazelle district, overwhelming their stability and triggering landslides that claimed lives, according to news reports.

Why is Papua New Guinea usually less prone to tropical cyclones?

Papua New Guinea lies close to the equator, where the Coriolis effect is weak. This effect is essential for spinning up tropical cyclones; without it, storm systems struggle to organize and intensify. As a result, the region sees significantly fewer cyclones compared to areas farther from the equator, such as the western Pacific or the Caribbean. However, in April 2026, unusually warm sea surface temperatures and favorable atmospheric conditions overcame this limitation. The warm water provided extra energy, allowing a low-pressure system to strengthen into a powerful cyclone despite the weak Coriolis force, demonstrating that equatorial regions are not entirely immune.

How did the slow movement of Cyclone Maila increase the landslide risk?

Slow-moving tropical cyclones are particularly dangerous because they deliver concentrated rainfall over a prolonged period. Maila's forward motion stalled near Papua New Guinea, so instead of passing in hours, its rainbands rotated over the same steep terrain for days. This continuous precipitation saturated the soil deeply, exceeding its capacity to absorb water. In mountainous areas like the Baining Mountains, the added weight of water and reduced soil cohesion turned slopes into mudslides. The Toriu River and nearby waterways became choked with sediment as landslide debris flowed downhill, illustrating how a cyclone's speed—or lack thereof—can be as critical as its wind strength.

What did Landsat 9 satellite imagery reveal about the landslides?

NASA's Landsat 9 satellite captured two images: one on September 24, 2025, before the cyclone, and another on April 20, 2026, after the landslides. The before image shows dense green tropical forests in the Gazelle district, with scattered white clouds. The after image reveals stark, light-brown swaths of exposed soil and debris cutting through the forest. These scars extend northward toward a river valley, contrasting sharply with the surrounding vegetation. The imagery also shows sediment-laden waters in the Toriu River, indicating heavy erosion and runoff. This visual evidence helped scientists assess the scale of the disaster and confirm that the landslides were triggered by Maila's intense rainfall.

How did terrain and rainfall combine to cause deadly landslides in the Gazelle district?

The Gazelle district in East New Britain features steep, forested slopes in the Baining Mountains. Tropical Cyclone Maila dumped exceptionally heavy rain on this vulnerable terrain, as measured by NASA's Global Precipitation Measurement (GPM) mission. The rainfall infiltrated porous volcanic soils, which are common in the region, but the prolonged saturation caused the soil to lose strength. Gravity pulled the saturated mass downhill, creating fast-moving debris flows. The steep gradient accelerated these flows, increasing their destructive potential. News reports indicate several deaths occurred, likely because residents had little warning as slopes failed suddenly. The combination of geological and meteorological factors made the area a perfect storm for landslides.

What role did warm sea surface temperatures play in forming Cyclone Maila?

Warm sea surface temperatures are the primary fuel for tropical cyclones. In April 2026, waters around Papua New Guinea were unusually warm, providing the heat and moisture needed to energize Maila. Typically, the region's equatorial location limits cyclone formation, but the warm water allowed a low-pressure disturbance to intensify. The ocean's heat evaporated surface water, which then condensed in the atmosphere, releasing latent heat and powering the cyclone's circulation. This process elevated Maila to a strong Category 4 system (Australian scale). Without the anomalously warm seas, Maila might have remained a weaker storm or dissipated entirely, highlighting the role of ocean heating in altering regional cyclone risks.

How do Australian and Saffir-Simpson cyclone scales differ for Maila?

Cyclone Maila was classified as Category 4 on Australia's cyclone intensity scale, but only Category 3 on the Saffir-Simpson scale used for U.S. hurricanes. The difference arises because the two scales use different wind speed thresholds and slightly different categorization criteria. Australia's scale defines Category 4 as having maximum sustained winds between 86 and 107 knots (160–199 km/h), while Saffir-Simpson Category 3 starts at 96 knots (178 km/h). Thus, Maila's winds fell into the upper end of Australia's Category 4 but the lower end of Saffir-Simpson's Category 3. This discrepancy does not diminish Maila's danger—it still packed life-threatening winds and rainfall that triggered the deadly landslides.