Alternative energy sources such as solar, wind and geothermal energies in Japan have been developing in line with the national energy policy of Japan ever since the first worldwide oil crisis occurred in 1973. Japan is abundant in geothermal energy sources which will contribute to protect the global environment because of low emission of CO_2 in terms of power generation. The nationwide systematic surveys of geothermal resources have been carried out in the volcanic regions, particularly in Hokkaido, Tohoku and Kyushu by public and private sectors since 1973. Those activities for geothermal exploration led to the birth of new geothermal power plants in rapid succession, and the current geothermal power generation in Japan is 533MWe in total from 17 power stations which is the fifth place in total generation in the world. The geological data about volcanic fields, especially calderas and basement geology beneath the volcanic regions covered with younger sediments, have been integrated by the nationwide geothermal resources survey carried out by NEDO since 1980 through geological, geochemical and geophysical methods associated with drilling works. The small-scale calderas such as Nigorikawa (Hokkaido), Sunagohara and Hijiori (southern Tohoku) in Quaternary age were selected as the promising areas for geothermal exploitation. A funnel-shaped caldera with steep walls was discovered in Nigorikawa through the drilling by private sector. The Nigorikawa caldrea was defined as one of the most common Japanese caldreas. The large-scale volcanic fields in Tertiary to Quaternary time such as Hakkoda, Sengan (northern Tohoku), Kurikoma (southern Tohoku) and Hohi (Kyushu) have been also surveyed in detail for geothermal exploration. The schematic models of calderals or "volcano-tectonic depression" (VTD) named Okiura, Old Tamagawa, Pre-Yakeyama, Sanzugawa and Shishimuta were proposed in those fields. The Quaternary granitic body (Kakkonda granite) was founded at 2,860m deep below the surface in the Kakkonda (northern Tohoku) through a deep geothermal well drilling by NEDO. The bottom-hole temperature at 3,729m deep should be higher than 500℃ because pure metal tellurium with the melting point of 449℃ was fused at the bottom of well. These data shows the Kakonda granite could have a possibility of the geothermal heat sources in Kakkonda. The Quaternary active volcanoes like Akan (Hokkaido), Akita-yakeyama (northern Tohoku), Hachijo (central Honshu), Unzen and Kirishima (Kyushu) are quite hopeful for goethermal development. Exploration wells drilled into or around those volcanoes were mostly successful in getting steam and hydrothermal fluids. A lot of useful information concerning the Tertiary granite and basement geology covered with younger volcanic sediments in Sengan, Kurikoma and Hohi have been accumulated by the geothermal exploration survey. Geothermal reservoirs have been initially recognized to be porous-type media underlying cap rocks which are similar to petroleum reservoirs. But the recent exploration survey results show that fracture-type reservoirs consisting of complicated fractures and/or faults are more dominant in the exploited fields. The Ogiri and Yanaizu-nishiyama geothermal power stations exploited in the last five years are characterized by the fracture-type reservoirs consisting of vertical faults with steeper angles. It has been becoming clear worldwide that geothermal activities have close relation to the formation of hot spring-type gold deposits. Prospective gold mineralization containing several tens grams Au per ton have been discovered in the fracture-dominated parts developed along the marginal zones of "cauldron" in the Hohi geothermal field by the surveys of MMAJ for the past more than ten years.

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The middle to upper Pleistocene formations distributed around Lake Kamo, Sado Island, are divided into the Ryotsu First, Ryotsu Second. Ryotsu Third, and Ryotsu Forth Terrace Deposits, and Ryotsu Younger Fan Deposit in ascending order. The Ryotsu Third Terrace Deposit called the Katabata Formation, intercalates the Katabata volcanic ash and the drifted pumices which are correlated with Kitsugi pumice fall deposit (K3) and Sambe-Kitsugi tephra (SK), respectively. The Ryotsu Forth Terrace Deposit is called the Agata Formation, and contains the Agata volcanic ash which may be correlated with the On-Pm1 or Pm-1A tephra. Brown-colored eolian soil deposits cover the terrace deposits, and are divided into the A to D Members in ascending order. Volcanic ash layers in these members are correlated with the marker tephras as follows: Akasaka B1 ash to On-Kt, Akasaka B2 ash to Aso-4, Akasaka B3 ash to DKP, Akasaka C ash to AT, Akasaka D ash to As-K. On the basis of relationship between the terrace deposits and these marker tephras, the Katabata and Agata Formations are correlated with the Shimosueyoshi and Obaradai Formations in the Kanto Plains, respectively. Depositional sequence of upper part of the Katabata Formation shows a typical upward-coarsening succession, and was formed by progradation of fan delta system. The altitude of foreshore sediments tend to become lower northward. This suggests that they are deposited at the regressive stage. The lower sequence of the Agata Formation shows a typical upward-finning succession. The upper sequence of the Agata Formation shows upward-coarsening succession in the northern part, while the sequence in the southern part includes nearshore and coastal plain facies, lacking foreshore facies. Depositional facies change of the Agata Formation shows a transgressive-regressive cycle. The formation was in barrier-island and estuary or lagoon systems in the transgressive stage, and in coastal plain systems in the following regressive stage.

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Paleo-Nagareyama Bay, an inlet of Inner Paleo-Tokyo Bay was formed in the Sakagawa lowland located in the northeastern part of the Tokyo lowland. The baymouth spits and shore platforms were developped around the area, during the late Holocene Jomon Transgression. The marine Holocene sediments distributed in the lowland are divided into two parts by an erosion surface with an altitude of 2.5m. The erosional surface, the data of ^<14>C age, and fossils of molluscan and diatom indicate that there existed two high sea-level episodes (about 5,800y.B.P. and 4,000y.B.P.) with a minor regression episode (4,500y.B.P.). The shore platforms in the Paleo-Nagareyama bay were formed during the two high sea-level episodes. The baymouth spits started to grow toward the southeast during the second high sea-level episode, and had closed the mouth within about 600years.

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Seasonal variation in depositional processes and hydrochemical phenomena of a tufa-depositing stream of Hokubo Town, Okayama Prefecture, was considered from hydrological and chemical data collected monthly from December 1997 to March 1999. The water issues from an underground water system of limestone and contains a large amount of calcium carbonate (up to 3.5 millimol/l in alkalinity). The water, as it flows along the stream, degasses CO_2, increases saturation index for calcite, and decreases Ca-contents by depositing tufas. The water chemistry data clearly show seasonal changes. The alkalinity, Ca contents, and PCO_2 of the springwaters were high in summer and autumn and low in winter and spring, that is associated with CO_2 production in the soil layer which enhances limestone dissolution in underground. The amount and efficiency of tufa deposition were large in summer and autumn and small in winter, that can be explained in terms of seasonal change in inorganic precipitation rate positively correlated with both activity products and water temperature. Amount of water flow is closely correlated to rainfall, especially a heavy rain within a week before causes large amount of water outflow. These seasonal changes are commonly recognized in other tufa-depositing locations in Japan. Calculated annual deposition of CaCO_3 in the stream of Hokubo is 2.9ton which is 14.6% of dissolved carbonate of springwaters.

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