Overview

Project Highlights:

  • The densely-populated Mexico City region is vulnerable to a wide range of volcanic hazards
  • Accurate assessment of hazard potential requires analysis of long term records
  • This project will analyse a new ICDP sediment core in conjunction with field data to construct the record of volcanism in the region since 300 ka – a major development on current knowledge.

The Mexico City region is one of the world’s largest urban areas, and is subject to a range of volcanic hazards, from scoria cone and lava eruptions in the Chichinautzin volcanic field, through to large explosive eruptions of regional stratovolcanoes such as Toluca and Popocatépetl. The exposure of the region to these different volcanic hazards cannot be precisely addressed without a good understanding of past activity. Field exposures across the area are relatively poor, limiting current knowledge to the recent geological past. To improve on this, this project will analyse and interpret a unique tephra record in a 350 m sediment core from Lake Chalco, on the southern edge of Mexico City. The core was collected in 2016 in a project funded through the International Continental Scientific Drilling Program (ICDP). Using fieldwork, dating techniques and the core stratigraphy, this project seeks to determine how the style, frequency and impact of volcanic hazards has varied in the Mexico City region over the past 500,000 years.

Popocatépetl, one of the active polygenetic volcanoes near Mexico City, has produced major tephra falls, pyroclastic density currents and debris-avalanches over its lifetime.

Methodology

The Lake Chalco cores comprise three parallel cores extending to over 350 m beneath the surface, and spanning ~500 ka. Tephra deposits occur throughout the sequence, and include both basaltic and more silicic compositions. The project will work with a composite core splice to produce a complete tephra-stratigraphy for the field site. A major aim of the project is to correlate major deposits with their source volcano, using glass and mineral phase compositions (electron probe and laser-ablation ICP-MS). Alongside this, fieldwork (in collaboration with local geologists) will sample major pyroclastic deposits are more proximal sites, with the aim of correlating them with tephras in the Chalco core. This will provide further constraints on event magnitude and impact, and also the opportunity to obtain better ages (40Ar/39Ar) for these eruptions. The record documented in this way will greatly extend the eruption history of polygenetic volcanoes in the region, and will then be used to explore the nature and impacts of eruptions and their frequency over the lifetime of the regional volcanic systems.

Training and Skills

CENTA students benefit from 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes. 

The project student will receive training in core sampling and sedimentological analysis, tephra preparation and geochemical analysis of volcanic glass (optical microscopy, SEM analysis, electron probe micro-analysis, and laser-ablation ICP-MS) and analysis of whole rock samples (XRF, solution ICP-MS). They will also receive training in volcanological fieldwork with the project supervisors and Mexican collaborators, and experience working as part of a major international project with researchers in other fields (e.g. palaeoenvironmental research being carried out on the Chalco cores as part of the this ICDP funded project).

Timeline

Year 1: Regional data compilation and literature review;  core sampling at LacCORE, Minnesota; sedimentological analysis; production of initial stratigraphy; initial fieldwork; tephra sample preparation.

Attendance and presentation at national volcanology conference.

Year 2: Geochemical and textural characterisation of tephras; selection and preparation of material for dating; possible follow-on fieldwork.

Writing-up of initial results, conference presentation and ICDP project meetings.

Year 3: Finalisation and synthesis of stratigraphic framework; statistical interpretation of eruption records and assessment of uncertainties; development of regional hazard dataset.

Writing-up of results for publication and thesis. Presentation at an international conference.

Partners and collaboration (including CASE)

The project student will be based at Birmingham but would work closely with the co-supervisors at Oxford and Leicester, and make use of laboratory facilities at a range of UK institutions. The student will build relationships with Mexican collaborators through fieldwork, and with the wider ICDP project participants, including the group at LacCORE core storage and analysis facility at the University of Minnesota, USA.

Further Details

Please contact Dr Sebastian Watt - s.watt@bham.ac.uk

This project will suit a student with an interest and facility for detailed laboratory work, statistical analysis of data, and an enthusiasm for volcanology.