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A simple theoretical model, based on the assumption that radon is transported by molecular diffusion combined with advective flow induced by barometric pressure, is used to investigate radon exhalation at three subsurface monitoring sites in the volcanic island of Tenerife, Canary Islands. The model is intended to filter out all known contributions to radon flux, in an attempt to find potential precursory signals of seismic and/or volcanic activity. For the period of observations (1 December 2000 to 1 April 2001), variations on radon concentration predicted by the model were in good agreement with those measured, confirming they were induced by atmospheric pressure changes.

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The spatial distribution of groundwater temperatures in the volcanic island of Tenerife, Canary Islands, has been inferred through measurements of water temperatures collected in the vast network of wells and subhorizontal tunnels, locally called ''galleries,'' which constitutes the main water supply of the island. The spatial coverage of the network of galleries allows us to reach from depth almost any geological feature of the island. The complex spatial distribution of temperatures in the interior of Tenerife is the result of the complex geological evolution of the island. Groundwater temperatures are greatly affected by groundwater flow and are considerably warmer in those galleries located in areas where water circulation is reduced due to the low permeability of materials and/or to the low infiltration rate of cooling meteoric water. In this sense, groundwater temperature should be characterized in quiescent conditions (background level), in order to facilitate monitoring changes in heat flow, such as those induced by ascending gases expected with an increase in volcanic activity.

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