Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 55 for “"tephra"”.
-
Tephra Transport, Sedimentation and Hazards
Tephra deposits are one of the possible outcomes of explosive volcanic eruptions and are the result of vertical settling of volcanic particles that have been expelled from the volcanic vent into the atmosphere, following magma fragmentation within the volcanic conduit. Tephra fallout represents the …
-
Volcanic Activity and Human Occupation of the Northern Andes: The Application of Tephrostratigraphic Techniques to The Problem of Human Settlement in The Western Montana During The Ecuadorian Formative
… to correlate and source subaerial fallout tephra deposits which mantle Formative Period archaeological sites in the western montana and the Quito basin of Pichincha Province, Ecuador. Excavations in the Tulipe valley defined the Nueva Era Phase occupation, 1200-335 B.C., and the Tulipe …
-
VOLCANIC EMISSIONS AND DISTAL PALAEOENVIRONMENTAL IMPACTS IN NEW ZEALAND
… palynological and geochemical changes following tephra fall at a range of sites across the North Island of New Zealand which were located at increasing distances from the main volcanic source, the Taupo Volcanic Zone. These sites collectively covered a wide variety of habitats existing under …
-
Documenting the Earthquake History of the Thousand Springs Fault in Summer Lake Basin, Oregon, USA
… relatively low sedimentation rates and numerous tephras from the past ~250,000 years and thus earthquakes on this fault are preserved and dateable through trenching. We dug two trenches across the TSF in 2019, exposing multiple episodes of offset bracketed by deep to shallow-water lake sediments, …
-
Resolving abrupt palaeoenvironmental changes in a lake sediment sequence from Ioannina, northwest Greece
… of core I-08. Detailed visible and ‘crypto-’ tephra analysis identifies deposits associated with explosive volcanism at Italian volcanic sources, including Campi Flegrei, Pantelleria, and the Aeolian islands for the first time at Ioannina. Two visible tephra layers, the Campanian Ignimbrite …
-
The Origin of Dark Mats at the Sunrise Ridge Borrow Pit Site (45PI408) Mount Rainier National Park, Washington
… Site stratigraphy is complicated, consisting of tephra deposits from mostly known origins that are intercalated with dark sediments of unknown origin, referred to here as dark mats. Precontact occupation has been split previously into two components based on the ambiguous depositional history of …
-
Studies on late Quaternary tephras in the Waikato and other regions in northern North Island, New Zealand, based on distal deposits in lake sediments and peats
… New Zealand, are investigated using distal tephras contained in lake sediments and peats. Such environments are advantageous for tephra studies, particularly in distal localities where tephra identifications have previously been difficult, because the tephras are preserved as discrete layers …
-
Data Potential of Archaeological Deposits at the Chelan Station Site
… and faunal artifacts buried beneath volcanic tephra from Mt. Mazama (6,830 BP). Artifacts were inadvertently discovered in buried soils within a secondary alluvial terrace during construction of a pipeline to supply water to the Beebe Springs Fish Hatchery. This thesis stems from participation …
-
Carbon Accumulation Rates Over the Holocene in Flow Country Peatlands and the Direct Comparison of Open and Afforested Peatland Carbon Stocks Using Tephrochronology
… ITRAX scanning was tested as a tool for finding tephra within peat and we found it be a highly efficient technique, both in terms of success rate and time. Three tephra layers were located across the Flow Country, improving our knowledge of tephra geochemistry and distribution as well as …
-
Mapping and Radiocarbon Dating Archaic Period Monuments: La Alberca Structure Complex, Highland Michoacán, Mexico
… are buried below a coarse consolidated tephra. Although more weathered, this tephra is similar to the oldest tephra in the bottom of La Alberca Rockshelter. The tephra is at least 7000 to 8000 years old (calibrated). Test trenching and probing, when combined with 3-D ArcMap …
-
Reconstruction of aspects of Northern New Zealand paleoclimate over the last 200 ka using laminated Auckland maar lake sequences
… Using revised ages of 12 rhyolitic marker tephra layers combined with revised ages for seven basaltic and two andesitic tephra, in addition to bulk carbon and pollen-derived radiocarbon ages, a new age model for the Onepoto Maar lake sediment sequence was established. In particular, the …
-
Drivers, Dynamics and Hazards of the largest pyroclastic eruptions of Tongariro Volcano, Central North Island, New Zealand
… eruption episodes produced at least 4.5 km³ of tephra. This "flare-up" far outstrips the averaged eruption rate of Mt. Tongariro of 0.1-1.0 km³/ka. Mapping of the individual tephra deposits of the Mangamate sequence revealed an 'unzipping' of eruption vents from north to south along the axis of …
-
Setting the Holocene clock using varved lake sediments in Sweden
… dating methods, i.e. radiocarbon dating, tephra isochrones and paleomagnetic secular variations were established for two sediment sequences in Värmland. These are the longest geological records with an annual resolution known to exist in Sweden. Three mid-Holocene Icelandic tephra horizons …
-
CO2 Adsorption On Volcanic Ash: Net Contribution Of Volcanic Eruptions To The Global Carbon Cycle
… were not measured. Co2 emissions and mass of tephra released from the eruption of mount Okmok were not measured. The calculations for adsorption percent for these two volcanos were performed using the ash/co2 ratio from mount Spurr and volcano Redoubt. The ratio was then applied to Okmok and …
-
Development of geochemical identification and discrimination by Raman spectroscopy. The development of Raman spectroscopic methods for application to whole soil analysis and the separation of volcanic ashes for tephrachronology
… successful geo-chemical identification of the tephras, a method reliant on electron probe micro-analysis (EPMA) to analyse major element composition. However, it is often impossible to differentiate key tephra layers using EPMA alone. Raman spectroscopy is commonly used in chemistry, since …
-
Long-range impacts of the ~74 ka Toba super eruption
… of the Toba impact by utilising cryptotephra as an absolute event marker of the eruption, resolving an age uncertainty issue that is persistent in proxy-based research in Quaternary sciences, eventually to be combined with palaeoecological methods for climatic and environmental …
-
UNDERSTANDING ERUPTIVE DYNAMICS, PLUME DISPERSAL AND PARTICLE TRANSPORT FOR RISK ASSESSMENT IN PAROXYSMAL MAFIC ERUPTIONS
… both on proximal and distal regions because of tephra fallout and ash dispersion. Characterization of eruptive dynamics is therefore fundamental to reducing the risk associated with these eruptions. This thesis presents a study of several lava-fountain episodes at Etna that occurred between 2021 …
-
The use of Geographical Information Systems for Disaster Risk Reduction strategies: a case study of Volcán de Colima, Mexico
… the modelled extent of pyroclastic flows and tephra deposition associated with a large-magnitude (VEI 5) eruption at VdC.<br/>The undertaking and analysis of a risk perception survey of the population enabled an understanding of the cognitive behaviour of residents towards the volcanic risk. …
Page 1 of 3