Archaeological exploration in Nicaragua using ground penetrating radar : a minor field study

This Master of Science thesis is based on data collected in Isla de Ometepe and León Viejo, Nicaragua. The project has been supported by the Swedish International Development and cooperation Agency and has been executed as a MFS. Nicaragua is a country with a known history of human activity of at least 7000 years. Many historic facts and sites still remain unknown and unexplored, which lead up to the purpose of this work: to try to increase the knowledge about two historically important places in Nicaragua using a geophysical method called GPR. The first site that was investigated is located on the slopes of the Maderas volcano on Isla de Ometepe. The island used to be a meeting place for Indian cultures and a central location for trade in the region from around 2000 years ago. The interest for this site has been to locate eventual building foundations in areas where previous villages are believed to have been located. The second site to be investigated was the area around León Viejo, an early colonial capital of the Spanish empire that was destroyed by a volcano eruption in 1610. The area has previously been investigated and many buildings have already been located, however it is believed that many buildings still remain unknown and that much more information can be found about this colonial settlement. The purpose of the study in León Viejo was therefore to explore areas of interest to locate eventual new findings. The method used in the project is GPR, a geophysical method that uses electromagnetic waves to investigate the ground in a non-destructive way. The method relies on different physical properties of the ground, which results in reflections of the radar waves that can be measured. The measurements on Isla de Ometepe turned out to be unsuccessful, mainly due to unfavourable ground conditions with highly conductive soil. The maximum penetration dept was no more than one meter and no significant objects or reflections of interest were located. In León Viejo the conditions turned out to be more favourable with a maximum penetration dept of about five meters. Both a 3D-model and visual comparison was made for the different sub-areas and signs of interesting reflections were found in mainly two areas. It is hard to know exactly what objects in the ground that has caused the interesting reflections, but some might be foundations of buildings or other objects related to colonial buildings. It can be concluded that on Isla de Ometepe the GPR method was not applicable with a 250 MHz antenna. It might be possible to reach better results on the same site with a different antenna or with another geophysical method. In León Viejo the GPR method have proved to be working well. The results from this study in León Viejo might be useful information for a coming excavation in the covered areas. A complementary study with one or several other geophysical methods might be advisable to confirm the results from this study.Validerat; 20101217 (root