Wednesday, June 02, 2010

Sinkhole appears after storm

A large sinkhole, some 70m deep, has appeared in the ground, swallowing two buildings, during a heavy storm in Guatemala City. Following more than 1000mm of rainfall in a single storm event, many instances of flooding and local landslides were also reported. It is likely that the sinkhole, formed from dissolution of limestone over thousands of years, was infilled with sediment which was washed away as a result of the storm. The link above goes to a clip of the sinkhole on the BBC web site.
The image is from There are some other spectacular images at

Tuesday, May 18, 2010

Hazardous landslide lake

In the Hunza Valley, Pakistan, a large landslide on 4th January this year blocked the valley, with the potential to produce a very large and hazardous lake. The initial landslide killed 19 and displaced 250 families. Since then attempts have been made to construct spillways to limit the volume of the lake, which is now about 20km long and 100m deep in places. 25,000 people have been evacuated by boat from the upper valley. The lake volume increased slowly in the winter, but in May, with the onset of summer and much melt water, the lake has increased rapidly in volume. Evacuation of 18 villages to 30m above river level is underway and warning sirens installed to aid last minute evacuation. The situation is extremely hazardous as the lake may now overflow within days. The exact size of the possible flood is obviously unknown but some estimate that it may exceed the 30m planned evacuation level. A web search for "Hunza Valley Landslide" gives a large amount of extra information.

Tuesday, April 27, 2010

Ice avalanche produces a “tsunami” in Peru

On Tuesday 13 April Rory McCarroll, Guardian Latin America correspondant, wrote an article entitled "Peruvian glacier split triggers deadly tsunami". A mass of ice 500m by 200m split of the Hualcan Glacier and dropped into a lake, "triggering a tsunami that breached 23m high levees". 50 homes and an important water processing plant were destroyed and at least one person was killed. Settlements in the valley were evacuated because there was risk of further ice avalanches. The town of Carhuaz, population 25,000 (Reynolds, 1992) and nearby settlements were affected. Carhuaz has been threatened by glacial flooding hazards in the past (Reynolds, 1998). Further outburst floods and related are likely as the glaciers in this region retreat under the influence of global warming.

Reynolds J.M. 1992. The identification and mitigation of glacier-related hazards: examples from the Cordillera Blanca, Peru. In McCall G.J.H., Laming D.J.C. & Scott S.C. (eds) Geohazards. Chapman & Hall, London 143-157.
Reynolds J.M., Dolecki A. & Portocarrero C. 1998. Construction of a drainage tunnel as part of a glacial lake hazard mitigation at Hualcan, Cordillera Blanca, Peru. In Maund J.G. & Eddleston M. (eds) Geohazards and Engineering Geology. Geological Society, London, Engineering geology Special Publications, 15, 41-48