Freeze-thaw cycles and rainfall as triggering factors of mass movements in a warm Mediterranean region: the case of the Tramuntana Range (Majorca, Spain) Abstract Between 2008 and 2010, the island of Majorca (Spain) experienced the coldest and wettest winters of the last 40 years. Accumulated rainfall was twice the average and values of intense rainfall up to 296 mm/24h were recorded, very similar to those calculated for a return period of 100 years. Additionally, high precipitation coincided with anomalous, low temperatures, with abundant snowfall and freezing in the highest zones of the Tramuntana Range, in the northwest sector of the island. As a result, 34 mass movements were recorded on the range, which seriously affected the road network in an area of great importance for tourism, as it welcomes 8.5 million visitors each year. Fourteen rockfalls, 1 rock avalanche, 15 landslides and 4 karstic collapses were inventoried. The geological structure, formed by a series of NW overlapping thrusts, determines the distribution as well as the failure pattern of the movements. Thus, the northern face of the range registered 68% of the mass movements: nine rockfalls with planar failure took place as well as all the landslides recorded. Likewise, south-facing slopes have been affected by longer runout rockfalls with a wedge-type failure. The thorough analysis of the meteorological data shows that most of the movements have taken place after antecedent rainfall over 800mm. Additionally, the rockfalls have also occurred after several freeze-thaw cycles, being a determining and unusual factor in this warm region. Intense rainfall >90 mm/24h also caused rockfalls as well as exceptional very intense rainfall >120 mm/24h caused landslides. The results aim to contribute to the design of an early warning system coordinating emergency, infrastructure services and meteorological centres in a region of high risk.

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In the present work, spectral analysis has been applied to determine the presence and statistical significance of climate cycles in long-term data series from different rainfall and gauging stations located in the Tramuntana Range, in the north-western sector of the island of Majorca. Climate signals recorded previously in the Mediterranean region have been identified: the ENSO, NAO, HALE, QBO and Sun Spot cycles as well as others related to solar activity; the most powerful signals correspond to the annual cycle, followed by the 6-month and NAO cycles. The incorporation of data derived from gauging stations contributes to better climate signal detection as local and exceptional influences are eliminated. Simulations have been performed for each rainfall/gauging station, using the most significant climate cycles obtained by means of the power spectrum. A good correlation between rainfall/flow values and simulated cycles has been obtained. The NAO and ENSO cycles are the most influential in the rainy periods, and specifically the NAO cycle, where a good correlation between episodes of high rainfall/flow and high values of ANAOI can be observed. At a second stage, landslides dated and recorded in the Tramuntana Range since 1954 (174 events) have been correlated with the simulated cycles obtaining good results, as the landslide events match rainfall peaks well. The correlation for the past decade (since 2005), when a detailed landslide inventory is available, also

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The Crestatx aquifer is the main source of water supply to the Bay of Alcudia, one of the largest resorts on the island of Majorca (Spain). This water has been used since the 1970s using several pumping wells, which draw an annual volume of 1.5 hm 3 . The seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level (up to 120 m) and dynamic water levels of down to 87 m below sea level. At the end of the 1990s, several sinkholes and subsidence depressions started being detected in a highly karstified area. Twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70,000 m 2 , with diameters up to 23 m and depth more than 15 m. The intense and continuous rainfall during recent years (2008)(2009)(2010) has considerably accelerated the process, increasing the dimensions of existing sinkholes and the appearance of new morphologies. By means of electrical tomography techniques, a ground study was carried out. Numerous cavities have been identified in the upper 30 m. Using a map of the surface morphologies and the geophysical profiles, we can determine that the propagation and orientation of the sinkholes lie along three main directions: N30°E, N130°E and N60°E. The first is the most relevant, which is parallel to the main tectonic structures in the area. The interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas, which is an effective tool to assess risk in the area, as there are roads and a housing development nearby. The high, but discontinuous, exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions, as it causes large variations of pressure and accelerates the dissolution process in the underlying rock.

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