NH
Natural Hazards

Natural hazard

Gaius Plinius Secundus and Sergey Soloviev, two names and awards.

Gaius Plinius Secundus and Sergey Soloviev, two names and awards.

The EGU has an award system in place aiming at recognising eminent scientists for their outstanding contribution in Earth, planetary and space science. There are different medals a researcher can be nominated to, including Division ones. Ah, before I forget: the deadline for this year nominations is 15 June! Don’t miss the chance to appoint an outstanding colleague. You can find more information on how to nominate candidates clicking on the EGU website.

The medals for the Division of Natural Hazard are two. One aims at recognising interdisciplinary natural-hazard research of scientists meeting the following criteria: outstanding research achievements in fields related with natural hazards, important interdisciplinary activity in two or more areas related with this topic, and research that has been applied in the mitigation of risks from natural hazards. This medal is named after Gaius Plinius Secundus. The second aims at awarding outstanding scientific contributions in fundamental research that improves our knowledge of basic natural hazards principles, as well as research that assesses and leads to the proper mitigation of natural hazards, from both human and environmental perspectives. This medal is named after Sergey Soloviev.

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Let the ash fall, but get ready for its consequences

Let the ash fall, but get ready for its consequences

The past 18th May marked 39 years since one of the most emblematic volcanic eruptions in historic times: the 1980 Mt St Helens explosive eruption. With a death toll of 57 victims, it is the deadliest volcanic event in U.S. history. If that wasn’t enough, it also destroyed hundreds of houses and roads. When we think about explosive volcanic eruptions what commonly comes in our minds about the possible related hazards are impressive Pyroclastic Density Currents (PDC) or Lahars (a glossary below), mainly because of their quick deadly potential, moving ashfall to a secondary role in producing hazards to population.

However, ashfall can be hazardous too even affecting people’s health in the long term and in distal areas from the volcano itself. In today’s post, we will go through how the fall of volcanic ash can be a hazard that must be taken into account by people living in the close (and sometimes not-too-close) neighbourhood of an active volcano. [Read More]

Alpine rock instability events and mountain permafrost

Alpine rock instability events and mountain permafrost
Rockfalls, rock slides and rock avalanches in high mountains

The terms rockfall, rock avalanche and rockslide are often used interchangeably. Different authors have proposed definitions based on volume thresholds, but the establishment of fixed boundaries can be tricky. Rockfall can be defined as the detachment of a mass of rock from a steep rock-wall, along discontinuities and/or through rock bridge breakage, and its free or bounding downslope movement under the influence of gravity[1,2]. Usually, we use this term when the volume is limited, and there is little dynamic interaction between rock fragments, which interact mainly with the substrate. Rockslides involve a larger volume (up to 100,000 m3) and the blocks often break in smaller fragments as they travel down the slope. In both rockfall and rockslide, the blocks move downslope mainly by falling, bouncing and rolling. On the other hand, rock avalanches involve the disintegration of rock fragments to form a downslope rapidly flowing, granular mass demonstrating exceptionally high mobility[3]. The size of these rock failures can vary from single boulders to several million cubic meters (e.g. the catastrophic failures of Triolet, 1717, and Randa, 1991).

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InSAR Norway: the big eye on Norwegian unstable rock slopes

InSAR Norway: the big eye on Norwegian unstable rock slopes

Marie Keiding is a researcher in the Geohazard and Earth Observation team at the Geological Survey of Norway. Together with her colleague, John Dehls, who is leading the project, she works to develop and operate the new mapping service called InSAR Norway.

Before we start, let’s briefly describe what is InSAR. First, the Synthetic Aperture Radar (SAR) is a day and night operational imaging system that can be operated from satellite aircraft or ground and has high capabilities of penetrating clouds because it uses microwaves. Its ‘interferometric configuration’, Interferometric SAR or InSAR, uses two or more SAR images to generate maps of surface deformation or digital elevation models. This is made by calculating differences in the phase of the waves returning to the sensor, as a function of the satellite position and time of acquisition.

Measurements of phase variations are possible only in those pixels of the image where the signal maintains a sufficient coherence between different acquisitions. For this reason, InSAR techniques are particularly suitable to monitor relatively small deformations, in the order of millimetres to centimetres.

Hi Marie, can you tell what is InSAR Norway?

InSAR Norway is the first free and open, nationwide, [Read More]