Ritter Island
Encyclopedia
Ritter Island is a small crescent-shaped volcanic island 100 kilometres northeast of New Guinea
, situated between Umboi Island
and Sakar Island
.
There are several recorded eruptions of this basalt
ic-andesitic
stratovolcano
prior to a spectacular lateral collapse which took place in 1888. Before that event, it was a circular conical island about 780 meters high. At about 5:30 am local time on 31 March 1888 a large portion of the island, containing perhaps 5 km3 of material slid into the sea during a relatively minor, possibly VEI 2
, phreatic eruption. Eyewitnesses at Finschhafen
, 100 km to the South, heard explosions and observed an almost imperceptible ash fall. Tsunami
s 12–15 metres high were generated by the collapse and devastated nearby islands and the adjacent New Guinea coast killing around 3000 people.
The collapse left a 140 metre high 1900 metre long crescent-shaped island with a steep west-facing enscarpment. 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.
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, situated between Umboi Island
Umboi Island
Umboi is a volcanic island between the mainland of Papua New Guinea and the island of New Britain. It is separated from New Britain by Dampier Strait and has an elevation of 1,548 m. Umboi is a Holocene complex volcano with no historic eruptions...
and Sakar Island
Sakar Island
Sakar Island is a volcanic island northwest of New Britain in the Bismarck Sea, at . It is a stratovolcano with a summit crater lake. No recorded eruptions are known.- References :*...
.
There are several recorded eruptions of this basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic-andesitic
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
prior to a spectacular lateral collapse which took place in 1888. Before that event, it was a circular conical island about 780 meters high. At about 5:30 am local time on 31 March 1888 a large portion of the island, containing perhaps 5 km3 of material slid into the sea during a relatively minor, possibly VEI 2
Volcanic Explosivity Index
The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....
, phreatic eruption. Eyewitnesses at Finschhafen
Finschhafen
Finschhafen is a district on the northeast coast of the Morobe province of Papua New Guinea. It is named after the port of the same name.The port was discovered in 1884 by the German researcher Otto Finsch. In 1885 the German colony of German New Guinea created a town on the site and named it...
, 100 km to the South, heard explosions and observed an almost imperceptible ash fall. Tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
s 12–15 metres high were generated by the collapse and devastated nearby islands and the adjacent New Guinea coast killing around 3000 people.
The collapse left a 140 metre high 1900 metre long crescent-shaped island with a steep west-facing enscarpment. 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.