Maciej Dąbski

LICHENOMETRIC AGES OF THE LITTLE ICE AGE MORAINES ON KING GEORGE ISLAND AND OF THE LAST VOLCANIC ACTIVITY ON PENGUIN ISLAND (WEST ANTARCTICA)

Abstract The recently observed recession of glaciers on King George Island is associated with decades of climate warming in the Antarctic Peninsula region. However, with only 60 years of glaciological observations in the study area ages of the oldest moraines are still uncertain. The goal of the study was to estimate ages of lichen colonization on the oldest moraines of the Ecology and White Eagle Glaciers on King George Island and on the Principal Cone of Penguin Island volcano. The first lichenometric studies on these islands from the late 1970s used rates that had about four to five times slower Rhizocarpon growth rates. We re‐examined the sites and measured 996 thalli diameters to establish the surface ages. To estimate the age we used (1) long‐term Rhizocarpon lichen group growth rates established by authors using data from a previous lichenometric study on King George Island, and (2) previous data of lichen growth rates from other sub‐Antarctic islands. Our results suggest growth rates between 0.5 and 0.8 mmyr–1. According to these rates the ages of the oldest moraine ridges are of the Little Ice Age and were colonized at the beginning of the twentieth century. The mid‐twentieth century age of lichen colonization on the historically active Penguin Island volcano might support the date of the last eruption reported by whalers in the end of the nineteenth and the beginning of the twentieth century.

Cavernous Weathering Forms in SW Iceland: A Case Study on Weathering of Basalts in a Cold Temperate Maritime Climate

Abstract The article is a case study of the development of cavernous weathering forms (alveoli and tafoni) on a sea cliff near Keflavik on the Reykjanes peninsula in southwestern Iceland. The majority of forms are found on vertical or inclined rock faces and cluster around the uppermost edge of the cliff. Single hollows gradually evolve due to back wearing of their sidewalls into complex caverns, until finally the whole outermost layer of basalt is removed. Particular attention is paid to mineralogical changes of basalts due to chemical and salt weathering. Chemical decomposition of feldspars, pyroxenes and olivines followed by precipitation of iron on and within the weathering rind, the presence of micro- and macro-pores such as gas bubbles and delivery of marine salts are proposed to be the key factors influencing cavern development.

Lichenometry and Schmidt hammer tests in the Kaunertal glacier foreland (Ötztal Alps) during the AMADEE-15 Mars Mission Simulation

Abstract The aim of this article is to show the results of the lichenometrical and Schmidt hammer measurements performed in 2015 during the AMADEE-15 Mars Mission Simulation in the Ötztal Alps in order to test the capabilities of analogue astronauts and collect information on the geomorphic history of the study area since the Little Ice Age (LIA). The results obtained differ significantly from our expectations, which we attribute to differences in the field experience of participants and the astronauts’ technical limitations in terms of mobility. However, the experiments proved that these methods are within the range of the astronauts’ capabilities. Environmental factors, such as i) varied petrography, ii) varied number of thalli in test polygons, and iii) differences in topoclimatic conditions between the LIA moraine and the glacier front, further inhibited simple interpretation. The LIA maximum of the Kaunertal glacier occurred in AD 1850, and relative stabilization of the frontal part of the rock glacier occurred in AD 1711.