Ritter Island

Ritter Island is a small crescent-shaped volcanic island north-east of New Guinea, situated between Umboi Island and Sakar Island.
There are several recorded eruptions of this basaltic-andesitic stratovolcano prior to a spectacular lateral collapse which took place in 1888. Before that event, it was a circular conical island about high.
1888 eruption.
At about 5:30 am local time on 13 March 1888 a large portion of the island, containing perhaps of material slid into the sea during a relatively minor, possibly VEI 2, phreatic eruption. Eyewitnesses at Finschhafen, to the south, heard explosions and observed an almost imperceptible ash fall. Tsunamis high were generated by the collapse and devastated nearby islands and the adjacent New Guinea coast killing around 3000 people.
The collapse left a high, long crescent-shaped island with a steep west-facing escarpment. At least two small eruptions have occurred offshore since 1888, one in 1972 and another in 1974, which have resulted in the construction of a small submarine edifice within the collapse scar.