OSB archive
OSB archive

From volcano to lab

Guest: David Ferguson

In this guest post David Ferguson of Oxford University's Department of Earth Sciences writes about his research into volcanoes:

Earlier this summer I took an unexpected journey to the Afar Depression, a vast remote desert in the north of Ethiopia.

The Afar region is famed among adventure tourists for it’s sweltering temperatures, saline lakes and numerous (and often active) volcanoes. It was the latter of these that was responsible for my impromptu trip.

On the 28th June an instrument carried by a NASA satellite, designed to measure temperatures on the Earth’s surface, detected a new area of intense heat emissions whilst flying over Afar. The most likely cause of this thermal signature was an active lava flow, the product of a new volcanic eruption. As soon as we received this data we raced out to Ethiopia to try and catch the eruption in progress. You can read about our trip on The Guardian's Science Blog.

A week after our sudden departure we were back in the UK. The souvenirs from our unexpected trip: a box of fresh lava samples, visual and thermal images of a newly formed volcanic fissure and some slightly melted shoes (new lava flows require very sturdy footwear!).

Afar is the site of intense geological activity, a manifestation of the Earth’s crust being split apart by the movement of tectonic plates. The key to why so much of this geological activity is concentrated here is the presence of great volumes of magma beneath the surface. Periodically, a batch of this magma surges upwards from deep in the crust, splitting the ground apart as it forces its way upwards and, in some cases, reaching the surface and erupting out onto the desert floor.

During the past few years Afar has seen a marked increase in this magmatic activity and every so often we get the opportunity to try and collect some samples of the magma from new lava flows. By studying the chemical composition and physical characteristics of these, currently rare, eruptions we hope to learn about the magma reservoir beneath the surface and also whether we can expect more eruptions in the near future.

A problem in forecasting volcanic eruptions in this part of Afar is that this type of volcanism is not often seen on dry land. As tectonic plates are split apart they tend to sink down into the Earth’s mantle (much of Afar is currently below sea level) and as such the areas where this geological process occurs (called ‘rifting’) are typically found at the bottom of the oceans.

There is, however, one other region on Earth we can use as a comparison to Afar without the need for a submarine. That is Iceland, where the fracture zone that splits apart the oceanic crust beneath the Atlantic Ocean takes a brief detour onto land. In the late 1970s Iceland experienced, over a nine-year period, a series of events similar to those currently happening in Ethiopia.  Using the data we gathered on the size and duration of this recent eruption (and also a previous one in 2007) we can compare our data to the pattern of eruptions seen in Iceland during that time.

Similar to Afar, the Icelandic activity began with several pulses of magma forcing their way upwards into the shallow crust, which, despite causing earthquakes and ground fractures, did not make it all the way up to erupt at the surface. 

However, as the magma continued to surge upwards over several years more and more eruptions occurred, most of these lasting longer and erupting more lava than the previous one. By comparing the patterns of earthquakes and eruptions observed in Afar over the past few years with the Icelandic data we have forecast that there is a high likelihood that over the next ten or so years this part of Ethiopia will experience several more (and potential much larger) volcanic eruptions.

Our findings on this are currently being peer-reviewed for publication in an academic journal. In the meantime, however, we will continue to monitor this part of Afar and to catalogue and study future activity.

You can read more about this work on the Afar Consortium website.

David Ferguson is based at Oxford University's Department of Earth Sciences.