No description available.

No description available.

The latest eruptive episode of Merapi volcano, Java, Indonesia, produced block-and-ash flows (BAFs) that affected the densely populated areas on the volcano's southern flank. The flows were not confined to the existing valleys but spilled over the valley sides to create overbank flows that resulted in fatalities and strong damages in the village of Kaliadem, -5 km away from the summit. This testifies the unpredictable behaviour of BAFs, not only at this volcano but also at similar locations around the world, and the need for an improved understanding of the flow transport and depositional mechanisms. In this respect, the new approaches, descriptive schemes and numerical simulations presented in this thesis address some of the key concepts of the dynamics and hazards of BAFs. The 2006 deposits were examined both immediately after flow emplacement and after the first rainy season following the eruption, allowing detailed correlations between their surface characteristics and internal architecture. Two main types of BAFs (short- to mediumrunout and long-runout BAFs) are recognized based on parameters including generation mechanism, flow volume, travel distance, deposit morphology, distribution, lithology and grain size distribution. The effects of topography on flow dynamics have been examined through the development of conceptual models for the two types of BAFs. Integration of high-resolution field-based data into numerical simulations using the Titan2D and VolcFlow models allows the validity of these models to be tested and rapid quantification of best-fit input parameters. Sensitivity analyses and inundation maps based on the probability of impact were used to produce a suite of potentially inundated areas from future collapse events affecting the Gendol valley and adjacent areas on the southern flank. Results provide the basis for defining hazard zonations of key areas at risk from BAFs at Merapi

This thesis focus es on marine interglacial sediments known as the Burtle Beds from the Somerset Levels of South-west England. Particular attention is paid to the palaeomorphology and palaeoecology of the southern arm of the Levels, known today as the Parrett Valley. The Burtle Beds are shown to be estuarine marine nearshore and intertidal sediments of interglacial age. Sedimentological and palaeoecological evidence supportsa, view that these sediments were deposited in an estuarine situation exhibiting variable salinity and tidal conditions. "--ý"- A consideration of the present ecological tolerances of estuarine faunas and floras, suggests MHWS tide levels in the region of 14-15m OD in the mid-estuarine regions but rising to c. 18. Om OD in the headward regions. The interglacial marine strandline deposits of the South-west have been reappraised and cursorily assigned to specific locations within the tidal spectrum at the time of deposition. The notion of dual or multiple "Ipswichian" (Last interglacial) sea level peaks is re-examined in the light of tidal amplitudes in the Bristol Channel. It is suggested that the evidence of the marine deposits in the Somerset Levels is consistent with a single sea-level peak of c. + 6. Om (during sub-stage 5e), amplified by tidal enhancement in the narrowing, shallowing Bristol Channel to leave storm beach deposits at heights up to 18m OD in the headward regions.

No description available.

No description available.

During the last glaciation the area was invaded by two distinct ice sheets. One, from the Irish Sea basin, pushed southwards across the Cheshire-Shropshire Plain and sent a lobe down the Vale of Stretton and onto the northern slopes of the Long Mynd. The other was nourished in the Plynlimon massif and advanced from the west. Directions of ice movement, inferred from the orientation of ice-moulded landforms, drumlins, striations and the distribution of erratics, are complex, but the broad valleys were the main avenues of advance. Drift generally occupies valleys and covers the lower hillslopes, while erratics and scattered patches of till are found at higher altitudes. At the glacial maximum all save perhaps the highest hill summits were ice-covered. The Stiperstones tors are unreliable indicators of an inglaciated enclave. Deglaciation was characterised by a gradual downwastage, retreat and stagnation of the margins of the ice. Complex systems of subglacial drainage channels were cut in the Vale of Strettoa, and on all the major hill masses up to 1,300ft. Kaure moraines deposited across the Onny valley at Lydham Heath and the Mule - Caebitra valley at Sarn, indicate pauses in the ice retreat. Kamiform topography is also a feature of the northern slopes of the Long Mynd and the Vale of Stretton. Several important changes in, the drainage pattern resulted from glaciation. The Mule and Camlad were diverted across pre-glacial watersheds through meltwater channels, while the Onny was diverted through an ice-breached col and meltwater channel at the southern end of the Long Mynd. Radiocarbon dating of shells in the drifts at Iron Bridge, and of other drifts on the margins of the Welsh massif, indicate that the last glaciation of southern Shropshire was of Main Wurm age.

This study, with fieldwork undertaken in the Pang and Lambourn catchments in Southern England, investigates the occurrence and distribution of rapid groundwater flow in the Chalk and evaluates the degree of karstification. A survey of surface karst features revealed a clear spatial pattern in their distribution with three distinctive geomorphological zones. Stream sinks and dolines occur frequently in Zone 1 where there is extensive Palaeogene cover. Only dolines are present in Zone 2 where Clay-with-Flints deposits overlie areas of the Chalk and there is little surface karst, other than dry valleys, in Zone 3 where the Chalk outcrops. Tracer tests from three stream sinks in Zone 1 demonstrated connections to springs and rapid groundwater flow (1-6 km.d-1) indicating connected networks of conduits and large fissures over distances up to 5.1 km. Rapid flow was accompanied by variable tracer attenuation. Unsuccessful results at two other stream sinks were probably due to total attenuation. Further investigation at one site using four dyes and one bacteriophage tracer demonstrated the occurrence of diffusion (probably into the Chalk matrix), but indicated that diffusion is only a minor contributor to attenuation. Very high tracer losses (~75 % of dye and ~ 99% of bacteriophage) appear to be due to transport down multiple flowpaths, many comprising at least one section in which flow is through narrow fissures and fractures. The Single Borehole Dilution technique was developed to identify the distribution of flowing horizons in all three zones. Flow horizons decrease with depth below ground level but have an average spacing of ~ 9 m. Comparison with borehole imaging data suggested that solutional enlargement of fractures to form fissures, tubules and small conduits is common in all areas, but that these features may have limited lateral extent. Overall the Chalk appears to be mildly karstic with small-scale karst development resembling the early stages of speleogenesis.

No description available.

No description available.