In tidal flats, the tides repeatedly cause drought and submergence. In particular, biological activities and chemical changes are active in the underground, and those activities are strongly controlled by the underground temperature. Understanding the underground thermal structure is considered to be one of the important issues in understanding the interrelationship between environment and function in tidal flats. In September 1996 and February 1997, we measured air temperature, ground surface temperature, and underground temperature (four layers) at Banzu Tidal Flat in Kisarazu, Chiba Prefecture. The following conclusions were obtained by dividing the state of heat transfer on the ground surface at night.
1) Values ​​of 0.002 to 0.005 (cm2/s) were obtained as thermal conductivity K for water-containing tidal flat mud.
2) In the surface layer of the tidal flat, it is necessary to consider not only the heat transfer from the surface but also the advection of heat due to drought and submergence.