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The University of Southampton
Ocean and Earth Science, National Oceanography Centre Southampton

Research project: Triggering of major volcanic eruptions recorded by cumulates

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The Las Cañadas volcano on Tenerife, Canary Islands generated at least seven major explosive eruptions during the last 3 million years. These catastrophic events produced >130 km3 of pyroclastic material, resulted in the formation of a caldera and devastated the island. Despite considerable scientific interest in the volcano and associated hazards including major landslides, little is known about the triggers for these large-scale events.

Las Cañadas volcano on Tenerife
Las Cañadas volcano on Tenerife

Crystal Cumulate Samples

We have recovered partially developed crystal cumulates (‘live' cumulate mush) ripped from the magma chamber beneath the volcano during these major eruptions. These represent "frozen" clumps of crystals stuck together with the final magma at the time of eruption. Many different types of cumulate are found in each of the pyroclastic deposits, revealing that the entire magma chamber was destroyed by each explosive event.

Fig. 1. Variation in Na:Ca:K  in a plagioclase cumulus crystal. Arrow highlights light blue Na-rich felsic rim. Scale bar =500μm. (Source: R Taylor)
Fig1 Na:Ca:K variation

What do these samples tell us?

Chemical variation across crystals can record changes in magma composition. In the central sections of the cumulate crystals fluctuations in chemistry reflect periodic influxes of basaltic magma. However, the final growth at the edge of these crystals consistently marks a change to more felsic magma (Figs. 1 and 2). This change links these explosions to magma mixing events that brought together felsic and basaltic magmas. Release of magmatic gas during this mixing is thought to be the driver for these catastrophic eruptions.

 

 

Fig.2. Compositional profiles and photomicrograph images of plagioclase (a and c) and clinopyroxene cumulus crystals (b and d). (Source: R Taylor)
Fig2 Compositional profiles

Key Contacts

Dr Rex N Taylor (Principal Investigator)

Dr Thomas M Gernon (Principal Investigator)

 

 

Fig. 3. Schematic  of the Las Cañadas magma chamber development. (Source: R Taylor)
Fig3 Magma chamber development

PhDs and Other Opportunities

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Associated research themes

Volcanic Processes

Related research groups

Geochemistry
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