- 著者
-
新堀 賢志
長井 雅史
金子 隆之
Fujii Toshitsugu
Nakada Setsuya
Yoshimoto Mitsuhiro
Yasuda Atsushi
Aoyagi Masanori
- 出版者
- 東京大学地震研究所
- 雑誌
- 東京大学地震研究所彙報 (ISSN:00408972)
- 巻号頁・発行日
- vol.82, no.2, pp.119-178, 2007
An archaeological excavation site at the northern foot of Mt. Vesuvius in Italy provided a three-dimensional outcrop with a height of 8m to study its volcanic succession. Through a stratigraphical study of sediments and chemical analyses of juvenile materials, the timing and the sequence of the burial processes of the villa, which is attributed to Emperor Augustus, have been revealed. The sediments filling the villa can be divided into five stratigraphical units (Group1, Group2, Group3A, Group3B, and Group3C) by the presence of soil. The lowermost unit (Group1) directly covering the partially collapsed Roman building includes air-fall deposits, surge deposit, and epiclastic flow deposits. One of charcoals found in this unit give an age of 1500yBP, and the juvenile scoria have the same compositional range as ejecta of the AD472 Sub-plinian eruption, and differ from ejecta of major eruptions. The next three units (Group2, Group3A, and Group3B) include thick epiclastic flow deposits interbedding air-fall deposits. The uppermost unit (Group3C) consists of alternating scoria and ash-fall layers and an overlying ash-fall layer. The petrographical features and the composition of juvenile materials coincide with those of the AD1631 Sub-plinian eruption. From these geological and geochemical features, the burial process of the Roman villa is described as follows. When the AD472 eruption started, the villa had partially collapsed. This damaged building was mantled by an air-fall deposit a few tens of centimeters thick. The remaining building was soon struck by several phases of lahars, and was buried up to a height of 5m. The villa experienced at least five eruptions, and their ejecta and subsequent lahars buried the building further. The last eruption, which completely buried the villa, was the AD1631 eruption. This reconstructed scenario suggests lahars generated just after the eruptions were major agents in the burial of the Roman villa.