Volcanological investigations in Indonesia were started in the 18th century, when Valentijn in 1726 prepared a chronological report of the eruption of Banda Api volcno, Maluku. Modern and intensive volcanological studies did not begin until the catastrophic eruption of Kelut volcano, East Java, in 1919. The eruption took 5,011 lives and destroyed thousands of acres of coffee plantation. An eruption lahar generated by the crater lake water mixed with volcanic eruptions products was the cause of death for a high number of victims. An effort to mitigate the danger from volcanic eruption was first initiated in 1921 by constructing a tunnel to drain the crater lake water of Kelut volcano. At the same time a Volcanological Survey was established by the government with the responsibility of seeking every means for minimizing the hazard caused by volcanic eruption.