THE SEARCH FOR IMPACT STRUCTURES IN NORWAY

The search for impact structures in Norway is still in its infancy and compared to Sweden and Finland the number of discovered structures (2 confirmed and 1 possible) is very low. The geological composition and comparable areal dimensions of the three countries would indicate rather similar number of impact structures.

A systematic search for topographic impact structures in Norway was therefore initiated late 2005 . The first phase was based on an automatic scan of digital elevation models (DEM) with spatial resolution between 25 m and 100 m. In this phase we defined topographic krater structures with diameters between 2 and 5 km, and correlated this core with the DEM (“matching”). The first screening picked out about 4400 circular structures, matching the topographic pre-described structure. Thereafter the different cases we briefly analysed manually (geological and geomophological setting), and the number of circular structures were reduced to 1201. These circular structures may be of several different origins, a few of them might have an impact origin. The goal was to visit and look up these structures in the field, but for our small project group this task was immense. Based on a website presentation (www.geo.uio.no/groper) and intensive national publicity of the project, we wanted to engage students in the search. The fall 2005 and spring 2006 students (age 10 to 14) and their classes participated in this hunt for impact structures in a national school project launched in co-operation with The Research Council of Norway.

The final results of this approach will be seen in the fall of 2006, when the different presentations have been submitted and awards handed out.

The scientific part of this project will continue with comparative analyses of available geophysical and geochemical information. This program is planned in cooperation with Geological Survey of Norway and with the University of Helsinki, Geological Survey of Finland and European Space Agency/ESTEC.