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During the nearly 40 years covered by the study, major height differences of over ± 25 m have been revealed in the volcanic landscape of the 1970 craters in Deception Island, an active volcano in the South Shetland Islands (West Antarctica). In the last 14 years, the mean volcanic filling rate has been 1 m yr -1 and the mean erosion rate has been -0.2 m yr -1 . There has been considerable landform modification mainly associated with landslide-induced accumulation, and erosion may indicate the craters' fill over the next 30-40 years. Deception Island's eruptions have been recorded since 1842. Special attention was paid to the zones affected by the most recent volcanic events and the geomorphological changes that have taken place in those zones since then (e.g. the 1970 volcanic craters area in the last episode occurring between 1967 and 1970). Historical maps (produced before and just after the 1970 eruption) were compared with maps plotted in 1992 and updated using a 2003 image from the Quickbird satellite and data obtained with Global Navigation Satellite System technology in 2006. Techniques used included both geodetic transformation and the geometric correcting of maps.

IntroductionAccording to Dragani et al. (2004), the first observations of the sea levels at Deception Island were made in 1991. Tidal data were obtained over four days in summer by a visual tide staff located near the Decepción Station (Argentina) geodetic benchmark (BARG). This geodetic benchmark, belonging to the Deception Island geodetic network (REGID), was used as the vertical and horizontal datum. Based on these tidal data, an orthometric height value of 2.547 m for the BARG was calculated. This orthometric level was translated by geometric levelling to the point LN00, the fundamental point of the levelling network of Deception Island (RENID); the mean sea level obtained relative to LN00 was 5. Instrumentation and dataData were obtained using two moorings, each with a SAIV TD304 bottom pressure sensor at points near the coast, obtaining average local values of depth of the tide gauge of 3.147 m at Deception Island and 7.475 m at Livingston Island. The tidal observations at DECMAR and LIVMAR stations were made between February 2011 and April 2013.Pressure (P), temperature (T) and conductivity (C) data were recorded at the stations with a CTD SAIV SD 204 sensor that has an accuracy of ± 0.02 ppt for salinity, S, (derived from P, T and C) and ± 0.01ºC for T. Additionally, AQUAlogger 520 PT were used. These sensors have an accuracy of ± 0.05°C for T and 0.005% of full scale (10 m) for P. The geometric levelling was made using a Leica model NA2 optical level with an accuracy of ± 0.7 mm for one kilometre double run levelling. The GPS data for positioning of benchmarks and stations were taken from Vidal et al. MethodologyTo convert hydrostatic pressure into a sea level equivalent height P = P a + ρgh was used, where P is the pressure registered by the sensor of the tide gauge, P a is the atmospheric pressure, g is the acceleration due to gravity (average value calculated for Deception Island is 9.822083 m s -2 ) and ρ the density of the water in the study area, calculated using the records of T and S.Vidal et al. (2012) used a constant reference value of 990.8 mb (hPa) as P a which corresponds to the average value of P a in the region during the period 1978-89 (Rakusa-Suszczewski et al. 1992. The sea level for any particular time can be corrected by adding or subtracting the changes caused by P a changes on the reference values: at low enough frequency the correction is c. -1 cm of sea surface height for every +1 mb (hPa) of P a (Chelton & Enfield 1986). For this study, records of P a were taken concurrently with the tidal measurements, obtaining average values of 988.39 mb at Deception Island and 987.27 mb at Livingston Island.

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