Large, long-lived volcanic systems are dynamic in time and space over a range of scales and are subject to competing, yet linked, volcanic, magmatic and tectonic forces (e.g., Hutchison et al. 2016). Unravelling the complex geological past of such systems is critical for defining their present and future states and geohazards. The island of Ischia, in the Bay of Naples, Italy, is the top of a large,
long-lived volcanic system with an extremely varied and enigmatic history.
Volcanic activity started >150 ka BP, and continued periodically until the most recent eruption (1302 AD). The magmas vary in composition from shoshonite to trachyte. Temporal variations in isotopic composition of the products emplaced since 55 ka indicate a complex magmatic system, characterized by phases of magma evolution under closed system conditions and by arrival of new, isotopically distinct magmas. As the island is permanent home to 60 000 people and is a popular tourist destination there is a pressing need to better understand its volcanic history.
This project will illuminate the volcanic, magmatic, and structural history of the island from around 55-20 ka BP. This period followed a major, M6, calderaforming eruption (Brown et al., 2008) that catastrophically changed the morphology of the island, and submerged its centre under the sea. This period also spans the onset of caldera resurgence, when a block of crust was uplifted >900 m by repeated magma intrusion in only a few tens of thousands of years. Synchronous with uplift were numerous eruptions from vents along the caldera margin and (later) concentrated in the eastern sector of the island.
The objectives are:
(1) Locate, document and interpret the deposits of eruptions on the island between 60-20 ka BP to understand the nature of post-caldera volcanism and its relationships with tectonic and volcano-tectonic features
(2) Use major and trace element geochemistry and Sr and Nd isotopic data to track changes in magma supply over time and investigate long-term magma evolution and recharge (open and closed system processes, and crustal contamination) following the destruction of the magma reservoir by caldera collapse.
(3) Use (1) and (2) to reconstruct the geological evolution of the island between caldera formation and caldera resurgence.
(4) Use the new data to correlate the onshore tephra deposits with distal terrestrial and offshore marine tephra layers using published geochemical data. This project will provide insights into magma recharge processes in frequently active caldera systems, and impacts that these processes have on volcanism and tectono-volcanic processes, and will provide critical missing data on one of Europe’s most hazardous volcanoes.
The project would suit a numerate Earth Science graduate student with a broad interest in volcanology and geochemistry, a strong demonstrable fieldwork record, and a sense of adventure. A willingness and capacity to learn Italian would be advantageous and encouraged.
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Figure 1. Pyroclastic deposits and lavas exposed on the southern coast of Ischia.