From the cosmic-ray exposure age data, (time scale 10⁷-10⁸ years), of the lunar surface materials, we discuss the gardening process of the lunar surface layer caused by the meteoroid impact cratering. At steady state, it is calculated that, in the region within 10-50 m of the surface, a mixing rate of 10^-4 to 10^-5 mm/yr is necessary to match the exposure ages. Observed exposure ages of the lunar samples could be explained by the gardening effect calculated using a crater formation rate which is slightly modified from the current crater population data.

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Sakurajima Volcano is one of the most active volcano in Japan. More than 700 explosive eruptions took place since Aug., 1974 through Dec., 1976. The biaxial surface tiltmeter was installed in Aug., 1974 at Arimura (3 km, SSE of the Minamidake summit crater) to monitor the ground tilt. The station was built on the Showa Lava (flowed in 1945). The tiltmeter was set in the cave of 3 m depth to reduce environmental noise. The tilt change didn’t exceeds 4-arc second from the start of the observation. Such a small change suggests that the station is on the stable basement and in good environmental condition. Since Feb., 1976 about one year record was studied to clear the relation between the tilt change and the volcanic activity. There is a tendency that the tilt change is smaller when the volcano became active and the number of eruption increased. But the tilt change is larger when the volcano is inactive. Tide causes 0.05 arc-second tilt in amplitude. The station is so near the shore and the crustal structure around the volcano is complicated that the observed tidal tilt is not coincident with the expected one owing to ocean loading effect. The main component of tidal tilt were determined by the least square method. M₂ is the most priminent. The M₂-amplitude determined from the data of 696-hour length varies in its amplitude about 10%. The E-W amplitude decreased on Jul., 1976 and recovered on Jan., 1977. This change seems to have no relation with the seasonal change of sea level or another meteorological condition. Change of elastic constant of the crust around the volcano may be the cause of this anomaly. But it is neccessary to analyze longer record for confirmation of this matter. An attempt to find out the minor anomaly of short period is tried. Filtered record and synthesized one based on the amplitudes and the phase determined by the least square method were compared. The anomaly of the N-S component was founded in the case of heavy precipitation, but the E-W component shows the anomaly when the volcano became active. Short term prediction of volcanic eruptions will be available if it is possible to minimize the meteorological effect in the tilt measurement.

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