13th lobes were named in the order they were formed. Collapsing of the lava dome began to occur when the lobes, pushed out by the newly supplied magma, started to give way on the slope, causing a phenomenon known as pyroclastic flows (in which debris and volcanic gasses flow down the mountainside at speeds of 100 km/h). The threat of further disastrous events prompted authorities to evacuate 12,000 residents from their homes. On June 3, 1991, the volcano erupted violently, possibly as a result of depressurisation of the magma column after a landslide in the crater. A pyroclastic flow triggered by the collapse of a lava dome reached from the crater and claimed the lives of 43 scientists and journalists, including volcanologists Katia and Maurice Krafft and Harry Glicken. The eruption activity continued until March 1995, with a temporary pause during its course. Between 1991 and 1994, the volcano generated at least 10,000 small pyroclastic flows, destroying about 2,000 houses. From 1993 onward, the rate of lava effusion gradually decreased, and eruptions came to an end in 1995. The 1990–1995 eruptions of Unzen were the first eruptive activities in the world where pyroclastic flows were recorded clearly and continuously on video (in the past, many pyroclastic flows, such as those on Mt. Pelee, were recorded either as photographs or on small-scale videos). 1991 eruption Mount Unzen is perhaps most famous for its destructive and fatal eruption on June 3, 1991, at 4:08 pm. This eruption caused the first large-scale pyroclastic flow, unprecedented at the time, which killed 43 people in the evacuation zone. Among these were French volcanologists Maurice and Katia Krafft, as well as American geologist Harry Glicken. The other forty fatalities consisted largely of those involved in the mass media, as well as firefighters, police officers, farmers and taxi drivers. Preparations The first debris flow in the Mizunashi River (located at the foothills of Unzendake) occurred on May 15, and others continued to occur in succession on the 19th, 20th, and 21st. Shimabara City made an evacuation recommendation to the towns in the Mizunashi River basin each time, resulting in smooth evacuation of residents and no human fatalities. However, on May 20, when the lava dome appeared on Fugen-dake, it continued to grow day by day, and on the 24th part of the dome collapsed and the first pyroclastic flow occurred. After that, small pyroclastic flows occurred frequently,