Lake Suigetsu is a "Miracle Lake" Where the Lakebed is Undisturbed
Mikatagoko (Five Lakes of Mikata) are representative scenic spots of the Wakasa region, known as the "Lakes of Five Colors" appearing in different shades of blue due to differences in water quality and depth. Lake Suigetsu, one of them, is deep with a maximum depth of 34m. Plankton remains and diatoms deposit on the lakebed from spring to autumn, and yellow sand and iron deposit from late autumn to winter, forming one layer per year (with an average thickness of about 0.7mm).
Lake Suigetsu has no rivers flowing into it, and because it is deep and the bottom lacks oxygen, no organisms live there, so the sediment on the lakebed was not disturbed. Furthermore, because the lake was not filled in due to fault activity, it was a lake with a miraculous environment set for the formation of varves.
Varves are layers formed one per year that piled up on the lakebed; in Lake Suigetsu, there are actually 45m of varves covering approximately 70,000 years. Since data such as past temperatures, precipitation, climate changes, changes in surrounding vegetation, floods, and earthquakes can be grasped on a yearly basis, it has become possible to analyze in more detail and further back into the past.
