Over the course of the last week, I’ve been working as a demonstrator on the Durham University 3rd year volcanology fieldtrip to Tenerife, so I figured I’d talk a bit about what we did and the geology of the island here. After a smooth flight from Newcastle and a relaxing first evening at our base in Los Cristianos, we began the first field day with a visit to El Chinyero scoria cone, the site of the most recent eruption on Tenerife in 1909.
We first asked the students to analyze the material they were sitting on – shards of glassy, vesiculated mafic scoria. We then pointed out the presence of lava bombs on the slopes of the cone, and discussed the difference between deposition of clasts as fallout (scoria)and ballistics (bombs). To demonstrate ballistics, we had the students throwing lava bombs and pine cones to represent ejecta of different shapes and densities, to show how these factors affect how the ballistics are distributed around the volcanic vent. Unsurprisingly, the students could only throw the dense angular bombs a short distance, with rounded pine cones and more aerodynamic, lighter bombs travelling further.
We then slogged our way up the steep side of the cone to get a better view of the edifice and determine the location of the vent. The view from above also revealed lava flow deposits from the eruption, which the students spent time getting to grips with in the afternoon. Some of their observations included rippled surfaces and sheared near surface bubbles in the lower flow units, and rubbly broken up surfaces in the upper flow units. These were interpreted as being produced by pahoehoe and A’a type flows respectively (shown below).
After a long day in the field, the teaching team gave some brief feedback on students notebooks in the evening, before heading to a local BBQ restaurant to consume vast quantities of steak (to set us up for the next day)!