Catastrophic debris avalanches represent a second volcanic hazard

Jul 18, 2014
Figure 1 from Roverato et al.: Location map of the Taranaki peninsula and distribution of debris avalanche deposits surrounding Taranaki volcano, New Zealand.

Volcanic hazards aren't limited to eruptions. Debris avalanche landslides can also cause a great deal of damage and loss of life. Stratovolcanoes, with their steep, conical shapes made up of lava and unconsolidated mixed materials, can reach a critical point of instability when they overgrow their flanks. This leads to partial collapse, and the product of this slope failure is a large-scale, rapid mass movement known as a catastrophic landslide or debris avalanche.

In a matter of minutes, a debris avalanche can drastically modify the shape and nature of the surrounding landscape, covering extensive areas (in this case, up to 27 kilometers away) and changing the normal water drainage system of the region.

About 25 thousand years ago, the biggest slope failure event known at Taranaki volcano, New Zealand, resulted in the Pungarehu debris avalanche deposit (DAD). Initial collapse of the proto-Taranaki volcano occurred near the Last Glacial Maximum, with snow and ice cover and substantial groundwater present. The collapsing, sliding, large blocks of edifice material, known as "megaclasts," were highly fractured by the generation and the depressurization event, forming pervasive jigsaw textures.

This study by scientists from Brazil, Mexico, and New Zealand provides a textural analysis of the unique features of this landslide. The authors examine grain sizes, sedimentary structures, and microscopic particle attributes and provide new insights into debris avalanche transport and internal evolution processes.

Their findings help to explain the formation of the highly irregular topography of debris avalanche deposits, with chaotically distributed (and probably temporary) zones of shear developing where softer lithologies occur in a collapsing mass, thus leading to differential velocity profiles of portions of the flowing mass in vertical and horizontal planes.

The authors write that their goal is not only to provide new insight concerning the transport and emplacement mechanisms of Pungarehu DAD, but to also improve understanding giant debris avalanche deposits worldwide.

Explore further: An earthquake or a snow avalanche has its own shape

More information: M. Roverato, S. Cronin, J. Procter, and L. Capra. "Textural features as indicators of debris avalanche transport and emplacement, Taranaki volcano." Geological Society of America Bulletin, B30946.1, first published on June 30, 2014, DOI: 10.1130/B30946.1

add to favorites email to friend print save as pdf

Related Stories

An earthquake or a snow avalanche has its own shape

Dec 20, 2013

Predicting earthquakes or snow avalanches is difficult, but to for instance reduce the related risks it is of high importance to know if an avalanche event is big or small. Researchers from Aalto University in Finland have, ...

New risk factors for avalanche trigger revealed

Apr 04, 2014

The amount of snow needed to trigger an avalanche in the Himalayans can be up to four times smaller than in the Alps, according to a new model from a materials scientist at Queen Mary University of London.

Image: Landslide and Barrier Lake near Oso, Washington

Mar 27, 2014

On March 22, 2014, a rainfall-triggered landslide near Oso, Washington, sent muddy debris spilling across the North Fork of the Stillaguamish River. The debris swamped numerous homes, resulting in the deaths ...

Viking 1 examines Mars' Ophir Chasma

Aug 23, 2011

During its examination of Mars, the Viking 1 spacecraft returned images of Valles Marineris, a huge canyon system 5,000 km, or about 3,106 miles, long, whose connected chasma or valleys may have formed from ...

Recommended for you

NASA image: Fires in the southern United States

1 hour ago

In this image taken by the Aqua satellite of the southern United States actively burning areas as detected by MODIS's thermal bands are outlined in red. Each red hot spot is an area where the thermal detectors ...

Software models ocean currents for oil and gas search

2 hours ago

A study involving the use of streamline visualisation has found the technology can help guide electromagnetic transmitter and receiver placements, thereby aiding the search for oil and gas on the seafloor.

User comments : 0