7.7-Magnitude Flores Earthquake Triggers Landslides on Three Mountains in NTT
A M7.7 earthquake in Flores triggered landslides on Mount Ebulobo, Mount Kelimutu and Anak Ranakah, with no signs of increased volcanic activity.
On Saturday, August 15, 2026, a magnitude 7.7 earthquake struck the island of Flores in East Nusa Tenggara (NTT), Indonesia. The temblor triggered landslides on three mountains in the region: Mount Ebulobo in Nagekeo Regency, Mount Kelimutu in Ende Regency, and Anak Ranakah in Manggarai Regency. The Geological Agency reported the landslides, which added to the list of impacts from the earthquake, which had already claimed over 40 lives. The quake also generated minor tsunamis along the northern Flores and South Sulawesi coastlines.
Geological Agency head Lana Saria explained that the landslides were caused by the instability of rock masses, particularly on steep to almost vertical slopes. Factors contributing to this instability included fractures and planes of discontinuity within volcanic rock, localized hydrothermal alteration, and weathering processes.
These conditions rendered some rock masses less stable, leading to the landslides. On very steep slopes, planes of discontinuity within the rock mass can create rock blocks, with their stability depending on factors such as orientation, dip, continuity, and surface condition.
Moreover, hydrothermal alteration in volcanic areas can alter the rock's mineralogy and mechanical properties. In areas with hydrothermal alteration, the transformation of primary minerals into secondary minerals—such as clay minerals—can weaken the rock mass and planes of discontinuity, particularly if the material becomes more water-saturated.
Even in rock zones that are relatively hard due to silicification, the presence of intensive fracturing can compromise rock stability, leading to the detachment of rock blocks or masses.
Lana emphasized that the earthquake triggered these landslides, with the predisposition to instability arising from the steep slope morphology, rock fractures, weathering, and localized hydrothermal alteration. Post-earthquake seismicity remained dominated by tectonic earthquakes and aftershocks, while volcanic parameters remained within normal ranges.
Written by urgent.news from Tempo.co English's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
