The sea-level changes since the Postglacial ages in the Hokuriku region are investigated by means of studying emerged topography, shell beds, submerged forests, sand dune and their ages.
As the result of investigation, the sea-level was higher than that of the present between 4, 500 and 5, 500y.B.P. along the east side of the Noto Peninsula and the Toyama Bay. While the present sea level is the highest at the Kahoku lowland on the southwestern side of the Noto Peninsula.
This controversial result has been solved by following considerations.
The coastal areas along the Toyama Bay consist of rock coasts and alluvial plains. The rock coast is uplift zone and the alluvial plain is subsidence zone generally in the order of 10^4-6 years. If uplift is severe in this region, emerged sea shells of older ages must be in a high place and sea level of younger ages must be in a low place. But the emerged sea shells clustered between 2 and 6m and higher than the present sea-level and their ages clustered in between 4, 500 and 5, 500y.B.P.
This evidence shows that the rate of eustatic sea-level changes is quicker than that of the uplift in the order of 10³ years.
Elevation of the boring site becomes the highest point of the sea-level so long as discussion was done about the boring cores. The present sea-level is the highest since the Postglacial age, because the altitude of the lowland is the same latitude of the present sea-level.