Complex weathering in drylands: implications of 'stress' history for rock debris breakdown and sediment release

Weathering studies have often sought to explain features in terms of a prevailing set of environmental conditions. However, it is clear that in most present-day hot desert regions, the surface rock debris has been exposed to a range of weathering environments and processes. These different weathering conditions can arise in two ways, either from the effects of long-term climate change acting on debris that remains relatively static within the landscape or through the spatial relocation of debris from high to low altitude. Consequently, each fragment of rock may contain a unique weathering-related legacy of damage and alteration — a legacy that may greatly influence its response to present-day weathering activity. Experiments are described in which blocks of limestone, sandstone, granite and basalt are given ‘stress histories’ by subjecting them to varying numbers of heating and freezing cycles as a form of pre-treatment. These imposed stress histories act as proxies for a weathering history. Some blocks were used in a laboratory salt weathering simulation study while others underwent a 2 year field exposure trial at high, mid and low altitude sites in Death Valley, California. Weight loss and ultrasonic pulse velocity measurements suggest that blocks with stress histories deteriorate more rapidly than unstressed samples of the same rock type exposed to the same environmental conditions. Laboratory data also indicate that the result of imposing a known ‘weathering history’ on samples by pre-stressing them is an increase in the amount of fine sediment released during salt weathering over a given period of time in comparison to unstressed samples.

Genealogies of Partition: History, History-Writing and 'The Troubles' in Ireland

Contemporary political disputes have a long history of expression and contestation through the genre of history-writing in Ireland. The role of history writing and political science writing during the nearly 40 years of the so-called 'Troubles' has been no exception to this. Battles between competing versions of what the conflict 'is about', mediated through academic and popular texts have themselves in turn become constitutive of it. This builds upon centuries of the representation of the complicated politics of this island as 'an issue' in British domestic politics - first 'the Catholic question', then 'the Irish question'. The location of political power outside the island for centuries has created successive battles for the representation of sectional interests in a metropolitan centre. The skills of propaganda, history writing, newspaper writing have consequently been deployed at a remarkable level of skill and intensity. In the recent period one of the consequences of this has been the removal from the debate of the actuality of partition; this builds upon a particular historical representation of partition as an historical inevitability. To seek to restore partition to the debate is not to call for its undoing but to recognise that seeking to circumvent debates about its origins in the key period of democratisation in Irish politics (1880-1920) has been counter-productive. This essay examines the genealogies of partition in Irish and international contexts in the light of these battles for representation, and aims to return a lost dimension to the debate about the so-called 'Troubles'in Ireland. The genealogy of partition is the issue that has been marginalised in academic study and this has affected both policy and politics.

'Ancient Enmities' and Modern Conflict: History and Politics in Northern Ireland

This article investigates the role of history and historical consciousness in deeply divided societies. It looks at the case of Northern Ireland. It argues that, while the conflict here is caused by contemporary divisions, perceptions of the past have had considerable influence. Recent years have seen efforts to change historical attitudes and this has aided political accommodation. An important lesson from the conflict in Northern Ireland points to the need to challenge such historical perceptions.

An 8000-year history of landscape, climate and copper exploitation in the Middle East: the Wadi Faynan and the Wadi Dana National Reserve in southern Jordan

Investigations of geomorphology, geoarchaeology, pollen, palynofacies, and charcoal indicate the comparative scales and significance of palaeoenvironmental changes throughout the Holocene at the junction between the hyper-arid hot Wadi â??Arabah desert and the front of the Mediterranean-belt Mountains of Edom in southern Jordan through a series of climatic changes and episodes of intense mining and smelting of copper ores. Early Holocene alluviation followed the impact of Neolithic grazers but climate drove fluvial geomorphic change in the Late Holocene, with a major arid episode corresponding chronologically with the â??Little Ice Ageâ?? causing widespread alluviation. The harvesting of wood for charcoal may have been sufficiently intense and widespread to affect the capacity of intensively harvested tree species to respond to a period of greater precipitation deduced for the Roman-Byzantine period - a property that affects both taphonomic and biogeographical bases for the interpretation of palynological evidence from arid-lands with substantial industrial histories. Studies of palynofacies have provided a record of human and climatic causes of soil erosion, and the changing intensity of the use of fire over time. The patterns of vegetational, climatic change and geomorphic changes are set out for this area for the last 8000 years.