Table 1.
Volcanic formation history, resulting rock facies, and key hydraulic properties (e.g., hydraulic conductivity, anisotropy, and effective porosity) for the seven hydrofacies as defined in this study.
| Period | Epoch | Age | Stratigraphy | Geological features | Hydrogeological properties | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Volcanic activity | Rock facies | Hydrofacies | Hydraulic conductivity | Anisotropy | Effective porosity | |||||||
| Ref. 44 | Refs. 48,59,70 | R 44,48,59,61,66,68–72,79,80 | [m s-1] | KV/KH | [%] | |||||||
| Quaternary | Holocene | Today | Shin-Fuji | Alluvium; Topsoil; Volcanic ash | Sedimentary layers: Gravel and sand | AL | 1 × 10-4 | 1 | 30 | |||
| 1,700 AC | Subashiri stage | d | Flank lava extrusion (incl. Hoei and Jogan eruptions) | Young volcanic gravel; Lava flows | ||||||||
| 0 AC | c | Explosive eruptions and collapses of flanks | Debris and thick lava flows; Scoria fall deposits | MF | 1 × 10-5 | 1 | 10 | |||||
| 2,000 BC | b | Central cone building | Lava flows intercalated with pyroclastic material (volcanic gravel, sediments) | |||||||||
| 4,000 BC | a | Low volcanic activity | ||||||||||
| 6,000 BC | Fujinomiya stage | Continuous voluminous lava extrusions | Lava flows, scoria fallouts and sand (Pyroclastic cones) | FV | 1 × 10-3 | 1/10 | 20 | |||||
| Pleistocene | 15,000 BC | |||||||||||
| 20,000 BC | Ko-Fuji | Hoshiyama stage | Explosive eruptions followed by major collapses of the edifice | Mudflows, fan deposits | OLFM | 1 × 10-6 | 1/100 | 10 | ||||
| 30,000 BC | Massive basaltic lava flows | OLF | 1 × 10-4 | 1/10 | 15 | |||||||
| Scoria deposit - Volcanic gravel, sand and silt | ||||||||||||
| 100,000 BC | Komitake and Pre-Komitake | Basaltic - Andesite lava with low K2O and TiO2 content | ASHKOM | 1 × 10-6 | 1/10 | 15 | ||||||
| Ashitaka Volcano | Loam layer - Basaltic to andesitic lavas and pyroclastic flow deposits | |||||||||||
| Hakone Volcano | Basaltic to andesitic lavas and pyroclastic flow deposits | BS | 1 × 10-8 | 1 | 5 | |||||||
| Iwabuchi Volcano | Basaltic to andesitic lavas and volcaniclastic rocks | |||||||||||
| Neogene | Plio-cene | Accretionary complexes forming the Misaka and Tanzawa mountains | Sandstone, conglomerate, mudstone and tuff | |||||||||
| Mio-cene | Fujikawa (SW), Nishiyatsushiro and Tanzawa (N-E) groups | |||||||||||
The hydrogeological properties are based on field observations (borehole investigations, pumping tests) and numerical modeling results from the National Institute for Advanced Industrial Science (AIST)128, which focused on the southwest of the Mt. Fuji groundwater system. The indicated age refers to the younger (upper) boundary of each stratigraphic interval.