This paper presents the first results from ground surface temperature measurements, which are most informative for localization of frozen ground during the winter season. Two representative sites in the Pirin Mountains were chosen for soil temperature observation, with respect to the exposition factor – Golyam Kazan and Sinanitsa. Microexposition has also been taken into account at the Golyam Kazan cirque, because of morphological differences at the opposite walls of the cirque.
Seasonally frozen ground has been established for the first time in the Pirin Mountains. Our measurements showed 5 to 7 months freezing period in the observed sites. It has strong relation with the exposition and the altitude. There are indications for seasonally frozen ground appearance above 2200 m on the west-southwest macroslope of the Pirin Mountains. Duration of the frozen period is greatest in the northern exposition and lowest in the southern.
A geomorphological study has also been started in the same sites, regarding establishment of relation between soil temperature variation and slope processes activity. Our observations confirmed that the exposition factor determines the type and the speed of the slope processes and also the size of the deposits particles. The warmer south slope of the Golyam Kazan cirque is producing finer sediments and therefore slower mass movements. The north slope is related with coarser materials and rock falls. Sinanitsa cirque – the site with west-southwest exposition, has a six-month freezing period and predomination of slow mass movement processes.
Further expanding of such measurements in the high mountains of Bulgaria could provide data about the spatial dimensions of the seasonally frozen ground and the freeze-thaw processes dynamics in Southern Europe.
Key words: ground surface temperature, seasonally frozen ground, slope processes activity
Topic: PHYSICAL GEOGRAPHY