In this paper, a new method for studying thermally induced surface reactions with submicrometer scale resolution is discussed. Thermal-induced chemical modification of palladium acetate (Pd(OAc)(2)) has been successfully demonstrated via a scanning thermal microscope that permits sequential temperature ramping of its resistive thermal probe. In-situ thermal conductivity contrast and dynamic morphological evolutions of the thermal decomposition process have been monitored with spatial resolution in the submicrometer length scale regime to reveal interesting phenomena whereby drastic variations in both thermal conductivity contrast and topography were observed at its thermal degradation temperature range. At 523 K, thermal-induced modification was found to occur predominantly at the peripherals of the Pd( OAc)(2) islands. However, almost instantaneous transformation to palladium (Pd) metal took place locally at 553 K within the thermal probe＇s dwell time of ca. 5 ms at each pixel point. The chemical identity of the newly formed Pd could be identified conveniently due to its distinct thermal conductivity contrast with its surroundings and subsequently confirmed by X-ray photoelectron spectroscopic (XPS) studies.