Post sponsored by NewzEngine.com

MIL OSI – Source: GeoNet Quake & Volcanic Alerts – Press Release/Statement

Headline: Volcanic Landslides

Volcano camera reveals some of its other secrets

Images from our camera on the north rim at White Island are usually dominated by the vivid white gas and steam plumes from the active vents. What is less obvious is the source of the single largest natural event on the volcano in historic time – the 1914 landslide. This was more deadly than any eruption has been historically.

Around 9 or 10 September 1914, a large portion of the Main Crater wall at White Island collapsed onto the crater floor and consumed a mining camp. Sulphur was mined for the manufacture of sulphuric acid and fertiliser.  At the time this was headlined as “the greatest eruption in the Dominion since Tarawera on June 10, 1886” (Bay of Plenty Times 21 September 1914). Ten sulphur miners perished; the only survivor was the company cat, Peter the Great.  

The exact date and timing of the landslide is not well known. The island was visited by a launch from Opotiki on 15 September, however the launch master was not able to attract the attention of people ashore and could not land due to the sea conditions and darkness. He returned on 19 September. On landing he was immediately aware that a disaster had struck. He returned to the mainland and organised a rescue mission, but no trace of the miners was ever found.  An unusual cloud of ‘black smoke’ was noted from the mainland above the island on 10 September and this is thought to be ‘dust’ from the landslide and the most likely day of the event.

The source area of the landslide can often be seen in images from our web camera on the north rim and extends from the crater floor to the sky line. At the time of the 1914 landslide much of the Main Crater floor was covered by a crater lake, much larger than the lake there today.  The landslide came down into this lake, mixed with water and then flowed across the Main Crater floor and into the sea. The landslide has left hummocky mounds across the crater floor. The top of these mounds are great places to take panorama pictures of the island. Scientifically this is classed as a debris flow and the mounds are known as debris mounds. Similar deposits are found around many New Zealand volcanoes (especially  Ruapehu and Taranaki).   

Landslides are a common feature of White Island due to the high steep walls and weak nature of the material in the walls. The latest moderate size landslide occurred during heavy rainfall in July 2004, when a landslide off the north wall crossed half way across the crater floor. The landslide dammed some of the small streams on the crater floor. But this was very small compared to the 1914 one, only covering about 7% of the area of the 1914 one.