Comparison of the Submarine 1888 Ritter and the Subaerial 1980 Mount St Helens Debris Avalanche Deposits
Abstract
The lateral collapse of Ritter Island volcano, Papua New Guinea, on March 13th 1888 was nearly twice the volume of the lateral collapse of Mount St Helens on May 18th 1980 (4 to 5 km3 compared to 2.8 km3) and the resulting landslide traveled about twice the distance (~75 km for Ritter and ~30 km for MSH). Both landslides descended valleys producing topographically - controlled deposit distributions. Sonar mapping and deep tow camera imaging indicate that the Ritter Island deposit is exceptionally well exposed for a submarine debris avalanche deposit, most likely due to its very young age. Comparing the Ritter and MSH deposits in terms of their geometry, areas of associated substrate erosion, and the development of different morphological facies, provides insights into the kinematic and mechanical similarities and differences between subaerial and submarine debris avalanches resulting from volcano lateral collapses. Although both deposits have block - rich and matrix - rich facies, extensive substrate erosion in the distal part of the Ritter Island landslide resulted in the incorporation of water - rich sediment and transformation of the debris avalanche into a debris flow rich in sediment intraclasts.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2005
- Bibcode:
- 2005AGUFM.V13F..01D
- Keywords:
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- 8400 VOLCANOLOGY;
- 8404 Volcanoclastic deposits;
- 8488 Volcanic hazards and risks