Presentation Information
[O12-P24]Geological structure of Matsushima -consideration of the white veins-
*Ayaka Momma1, *Aoi Nakatsuka1, Misa Ikegaya1, Satoru Tayama1 (1. Miyagi Prefecture Sendai Daisan High School)
Keywords:
Matsushima,clastic dike,Pumice tuff
Matsushima is one of the most beautiful places in Japan. However, there are many things that are not understood from a geological perspective. One example is “White veins.” We researched previous studies about them, but we couldn’t find any. So our objective is to reveal how white veins formed. Moreover, it’s to find a relationship between the terrain of Matsushima and white veins. We conducted fieldwork and found that the ending of them is spreading and they are surfaces, not lines. Also, we made stereonets of them, finding they have trends that are high angles. Further analysis revealed, although Matsushima formed by five types of layer, white veins could only be seen in Pumice tuff containing andesite breccia layer. (Mt1) From our investigation about Mt1, it was made by pyroclastic flow. With these results, we think white veins were made this way; an underwater volcanic eruption occurred, and as it cooled from the outside in, an unconsolidated layer infiltrated the structure. About the relationship between the terrain of Matsushima and white veins, the spots that can be seen white veins rarely have islands, but other spots of Matsushima have islands in the northwest-southeast direction. So we think white veins makes it difficult to form islands.