Significant pyroclastic flow from Semeru on 7 April (image: Pusat Vulkanologi dan Mitigasi Bencana Geologi)A strong eruption occurred at the volcano on 7 April.At about 05:30 PM local time, a massive pyroclastic flow descended over the southern slope. The block-and-ash flow has been likely triggered by the gravitational collapse of the lava dome in the inner summit crater as well as the lava flow on the steep slope of the volcano. It also formed secondary ash columns (so-called phoenix clouds), as can be seen in the image, and rose about 2 km above the summit.Pyroclastic flows are deadly, turbulent hot avalanche of lava rock fragments of all sizes embedded in a mixture of turbulent gas and ash racing down slopes.Avoid all activities within 8 km of the summit in the southeastern sector along the Besuk Kobokan river, which is currently the most hazardous area.Beyond the 8-km zone, people should also stay at least 500 meters away from the riverbanks along Besuk Kobokan, as this area remains at risk from potential expansion of pyroclastic density currents and lava flows, which may travel up to 13 km from the summit.