Dr Nina Jordan

Dr Nina Jordan - Volcanologist

Honorary Visiting Fellow

Direct Contact:
E: njj5 [at] le.ac.uk

Research interests:

  • Physical volcanology, in particular welded ignimbrites
  • Igneous geochemistry & petrology, in particular of peralkaline volcanoes
  • Volcanic hazards

PhD research: Eruptive history of the peralkaline caldera volcano at Pantelleria, Italy

Supervisors: Dr Mike Branney and Dr Mike Norry. With help from Dr Rebecca Williams (U. Hull).

I am investigating the explosive eruptive history of Pantelleria caldera volcano in Italy. Several caldera-collapse eruptions occurred in the last ~300 ka; each emplaced a widespread rheomorphic ignimbrite, and distal tephra. Much recent work on the island  has been on units younger than the last caldera-collapse eruption (the well-known 46 ka ‘Green Tuff’). Instead, my study focuses on the older history of  the volcano. The oldest dated rock is 324 ka old although there may be older rocks on the island.

Aerial photograph of Pantelleria Island. Inset shows its location in the Mediterranean Sea.
Aerial photograph of Pantelleria, Mediterranean Sea (courtesy of University of Tübingen, Germany). Pantelleria town lies in the NNW of the island. The green areas are vegetated; these are areas of higher altitude (up to ca. 830 m) and extensive lavas. In the E two caldera scarps are visible (dark lines).

Much of the pre-Green Tuff stratigraphy is exposed in sea cliffs.
Much of the pre-Green Tuff stratigraphy is exposed in sea cliffs.

Methods

  • We are dividing the volcanic stratigraphy into ‘eruption-units’, each bounded by palaeosols (soils) that represent periods of repose.
  • Eruption-units were logged in detail to record variations in grain size, clast content, bedding, lithofacies etc in multiple locations as lateral variation can be substantial.
  • Each eruption-unit has been sampled laterally and vertically to characterise its the petrology and chemistry.

Navigating sea cliffs can be tricky and ideally involves using a boat.
Navigating sea cliffs can be tricky and ideally involves using a boat.

Some results and conclusions

Localised felsic eruptions, mostly on or near caldera faults, have produced small ignimbrites, pumice falls and lavas and have occurred throughout the entire ≥324 ka volcanic history. Their dispersal is limited and does not exceed several hundred metres so they are best termed strombolian.

In contrast, the larger eruptions involving caldera collapse and eruption of ignimbrites, only occurred in the last ~200 ka. Each eruption-unit contains a nonwelded to welded or rheomorphic ignimbrite, most with local lithic breccias. The breccias contain cognate and accidental blocks, and may record caldera-collapse-events. There may have been up to five partial caldera collapses, in contrast to widespread belief that the island underwent two collapses. There is no evidence for temporal cyclicity in the volcanic activity.

Ignimbrite‐forming eruptions are trachytic and rhyolitic in composition and are commonly chemically zoned with enrichment factors of ~2. Two extreme cases have enrichment factors of 4.5 and 7. Enrichment factors seem to be higher after longer repose periods. The chemical variation is chiefly seen in incompatible trace element concentrations, while major element variations are small, in line with observations at other peralkaline volcanoes. Due to the chemical heterogeneity, ≫1 sample is required to characterise a formation. Samples should be taken at the base and top at multiple localities. Also, it is not possible to correlate eruption‐units based on chemical data alone, knowing the stratigraphy is paramount.

Several Mediterranean peralkaline tephras correlate with the newly defined eruption-units:  distal ashes have been found for all but two eruptions. Interestingly, distal tephras do not in all cases have the same chemical fingerprint as their proximal counterpart due to not all parts of an eruption generating far‐travelled ash. The furthest recorded ash has been found at a distance of 1300 km from Pantelleria. If an ash is found in more than one distal location and thicknesses are known, isopachs can be constructed which can be used to determine the eruption volume. In this way, we have arrived at volume estimates of up to 26 cubic kilometres, much larger than previous estimates.

Example of a distal ash distribution related to an eruption from Pantelleria.
Example of a distal ash distribution related to an eruption from Pantelleria.

Volcanic evolution of South Pacific Arcs (VESPA)

After finishing my PhD I got involved with an IFREMER science expedition to explore submarine volcanoes in the Southwest Pacific. We were doing seismic lines and took seafloor samples from the Norfolk Ridge and Three Kings Ridge to establish the history of subduction and volcanism. Read more about it on the mission blog:

http://wwz.ifremer.fr/ncal/Bienvenue/Carnet-de-bord-VESPA

ECORD Research Grant for Outstanding Students

To follow up some of the tephra work from my PhD I have been awarded a grant to go and sample IODP cores at the Bremen Core Repository. Sampling took place in September and analysis of the tephra shards is ongoing. Watch this space!

Contact Details

Nina Jordan
Nina Jordan

If you have any questions or comments, feel free to contact me at njj5 [at] le.ac.uk or +44 (0)116 252 3920. Also check out my LinkedIn profile: https://www.linkedin.com/in/nina-jordan-phd-60140b46.

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