Understanding Extreme Geohazards: The Science of the Disaster Risk Management Cycle

European Science Foundation Conference
November 28 to December 1, 2011, Sant Feliu de Guixols, Spain

Session 5 “Predicting increased risks for extreme hazards: volcanoes and landslides.”

Discussion: “How safe are sleeping volcanoes?”

Roger Urgeles Esclasans

Most of the open questions I refer to here are related to submarine landslides, but some may apply to volcanic settings too:

  1. Submarine landslides are events of extremely large magnitude (1-2 orders of magnitude larger than their subaerial counterparts). Yet the largest events occur at very low recurrence rates. Risk is approximated using the formula: Risk = Hazard x Vulnerability that can be approximated by: Risk = P of Occurrence (Hazard ) x Consequences. For many extreme events the probability of occurrence is very small but the consequences might be very large therefore we approach a problem of the type: Risk ~ 0 x infinite. How can we estimate the risk in such situations?
  2. Earthquakes occur over delimited areas that can be readily identified by faults, while submarine landslides may occur anywhere on continental margins with little diagnostic features. Monitoring provides early warning capabilities and insights on the problem under study. Are there areas that are well suited for monitoring of submarine landslides? Are there tools to monitor submarine slope activity over wide areas? What parameters should be monitored to predict the timing of failure of a submarine slope?
  3. During the last 2-3 decades bottom waters in Arctic environments have increased temperatures by up to 1oC due to climate change. Methane plumes rising from the sea floor have also been detected in these areas, at the place where gas hydrates occur. While it is not clear whether these plumes result from a methane background flux, these facts open new questions with regard to the stability of Arctic submarine slopes: How rapid those temperature increases diffuse below sea floor? How this affects methane hydrate dissociation and dissolution? How fast ensuing pore pressure dissipates? What is the slope stability of these regions?
  4. What could be a submarine landslide extreme geohazard study site?