John Maclennan
What sort of work does this research involve?
First of all, we go and collect rocks, usually from young volcanoes.

Emma Passmore collecting basalt at Kilauea, Hawaii
Emma Passmore collecting basaltic lava at Kilaueau volcano in Hawaii         
Sampling with the Alvin submersible at 2700m on the EPR
Sampling young lava at 2700m depth on the floor of the Pacific ocean. Alvin submerisble dive 3970 (Hickey/Perfit/Maclennan)

Then, we take a good look at what we've got.

describing Alvin samples onboard the Atlantis
Describing Alvin samples while afloat in the Equatorial Pacific on the Atlantis.
Dave Christie and John Maclennan examing samples on the Joides Resolution
Examining drill core from IODP Expedition 312 with Dave Christie.              

Next, the composition of the lava and the crystals that it contains are measured using a number of geochemical techniques, including ion microprobe, electron microprobe and X-ray fluorescence.

Fe content in glass and crystals in an Icelandic basalt
Map of the iron content of crystals (green-red) and volcanic glass (blue-purple) in a lava sample from Iceland.
Borgarraun melt inclusion compositions
Plot of geochemical observations from Iceland used to understand magma chamber processes.

These observations need to be compared with the predictions of physical models of the processes that operate inside the earth. In order to develop the models, a set of governing equations will be scribbled down (such as these). Usually we solve these equations by writing some computer code.
 
Results of a computer model of a thermal balance appropriate for the internal structure of undersea volcanoes, such as those being sampled by submersible above. The top of the model (z=0 km) is the seafloor. As you might expect, the earth is hot where magma is supplied at the left hand side. We can find out where this melt is stored before eruptions bt comparing the model results with observations. The blue, green and yellow colours show rocks that have supplied heat to geothermal circulation. Results of thermal model for a mid-ocean ridge

Finally, the findings of the study are written up into papers and presented to colleagues at international conferences. We then start to plan the next phase of sampling.

Unknown person sampling recent etna lava flow
Collecting samples at Etna. Photo by Sarah Collins.
The Brandur tuff-cone in south-east Iceland
The Brandur tuff-cone in South-East Iceland

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