Wednesday, March 23, 2011

After the disaster

It was huge. What more is there to say? Japan was prepared as the big one has been expected for a long time. Still, the M 9.0 earthquake and tsunami devastated the whole coast line. Natural disasters always strike out of the blue no matter how well prepared a country is. Total preparedness will never happen and zero vulnerability is a dream that will never come trough. This applies to Japan as it applies to a small scale natural disaster that struck western Norway a couple of days ago. Two people died in a snow and mud avalanche

Composite disaster are characterized by additional major hazards and disasters following the main trigger. In San Francisco in 1906 the fires that were started in the wake of the earthquake destroyed huge areas, as was the case in Tokyo after the 1923 Kanto earthquake. Almost half of Tokyo was destroyed by the flames. In addition, tsunamis are relatively common following major earthquakes below oceans, like in Asia in 2004, Chile 2010, or in Japan. What makes the current situation in Japan different is the possible consequences for the reconstruction if the nuclear disaster escalates.

I the mean time geologists try to understand the earthquakes and wait to see if the fault line that was active in 1923 can be reactivated. The activity in the main fault in the Japan Trench is still high, with more that 230 registered earthquakes the last week. Three earthquakes with M >6.4 occurred yesterday. 

 Earthquakes in Japan the last week.

Cities always rebuild after major natural disasters, but it remains to be seen what will happen near the nuclear plants in Japan.

Wednesday, March 9, 2011

The nicest columnar joints ever?

The picture this week is from the beautiful village Saint-Flour located about 80 km south of Clermont-Ferrand in the Massif Central (France). You see a lava flow with spectacular columnar joints overlain by a massive flow unit (picture 1). Saint-Flour is built on top of these basaltic flows (picture 2) that once poured out of the volcanoes forming the Massif du Cantal. 

 Picture 1: The columns in Saint-Flour.

Picture 2: Saint-Flour.

The volcanism in the Massif Central is young and rather odd. The most recent eruptions took place some 4000 years ago. Why are there volcanoes in this area at all? Is it linked to the Alpine deformation or to crustal spreading in the Atlantic?  

The volcanoes in Massif Central are numerous, ranging from lava domes to cinder cones, maars, and stratovolcanoes. In the north, the spectacular Chaine des Puys contains a great number of cones and maars, and one of the cones is partly excavated (the Lemptégy volcano; picture 3) as a part of the Vulcania theme park. Is this the best place in the world to see the internal structuring of a volcano, with fumaroles deposits, scoria, feeder dikes and lava flows? 

 Picture 3: Inside the volcano on a veeery gloomy day.

All of the prominent mountains in Massif Central are volcanic in origin, like the tallest one, Puy de Sanchy at 1885 m and Mont-Dore (picture 4). Further to the west, volcanic plugs dominate both the natural and cultural landscape (pictures 5 and 6).

 Picture 4: Mont-Dore in April/May.

Picture 5: One of the plugs in Puy-en-Velay. 

 Picture 6: Puy-en-Velay.

I wonder if the volcanoes will be brought back to life some day. Strictly speaking, they are only dormant.

Tuesday, March 1, 2011

The girl from Sahel

We were lost. Lost in the sandy Sahel of northern Mali. The Toyota 4x4 managed the terrain well, but we couldn’t track our position on the map. The Sahel stretched out endlessly in all directions, and today the landscape was partly masked by the sandy veil lifted by the strong winds. What to do now? Should we try to follow the tracks back to M’Bouna, the village we came from? We chose to continue. The guides told us that we might get lucky and still find the localities we were looking for: Areas with a red oxidized soil or sediment layers that were apparently formed from the heat emanating from shallow volcanic intrusions. 

We continued and came across a small valley with some trees and a water well. A few guys rose among the animals (picture 1) and came to meet us.

(Picture 1)

They gave us new directions and we moved on. After a while we drove through a small settlement with Tuareg nomads (picture 2). We stopped, and the guides got out of the cars and talked to the locals. I stayed in the car.  

(Picture 2)

Kids came running to see what all the fuss was about. I pulled down the window and took a few pictures. The kids didn’t seem to mind. On the contrary. They boys wanted their pictures taken, and to see the results on the camera screen. They all got very exited. Then a girl, somewhat older that the boys, pushed them aside and pointed at the camera before she closed her eyes. I took her picture. She had a look at it and smiled. We left the settlement, and continued our search. 

(Picture 3)

Later that day we found the red rocks, and took some samples. The landscape seemed endless. Sand-polished rocks with thick weathering crusts were silent witnesses of the passage of time and climates. I took a picture before we headed back to M’Bouna.

 (Picture 4)