Pyroclastic flow from Semeru this morning (image: Pusat Vulkanologi dan Mitigasi Bencana Geologi)A strong eruption occurred at the volcano this morning.At about 09:30 AM local time, a 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 700 meters 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.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.