Janine Krippner
I am fortunate to have worked with student Ash Harden at the University of Bristol, UK, during my time in Tenerife last year. We had a call about their master’s research on pumice rafts so that I can share the latest science with you.
Janine Krippner
Pumice is frozen magma foam, forming when magmatic gas bubbles expand and quickly cool into rock.
Submarine eruptions within a range of shallower water depths can produce enough pumice to form enormous rafts. These sheets float across the ocean surface.
Rafts form through several processes. A raftini (unofficial term) is a small pumice raft that forms when pumice falls from a cliff into water. Pumice can also enter the ocean from the air, settling out of an ash plume.
Pumice rafts can circulate for quite some time. One eruption in 1962 at Protector Shoal in the South Sandwich Islands formed an impressive raft that floated across 20,000km over three years.
Sea vessels encounter pumice rafts and we need to know how much damage this can cause. This is important for passenger vessels like yachts and ferries, and shipping vessels that can have international implications.
Ash is using lab experiments to research how pumice abrades or damages marine materials. They use a wave flume tank, which is a long tank partly filled with water and has a mechanism in it to produce waves. Within this is a thin layer of pumice at the surface, and different materials suspended in the water. This moves the pumice back and forth against the materials to simulate a real-world environment.
The next step is drying and weighing the materials to see how much material has been worn away by the abrasive pumice. A timelapse camera tracks the action.
They then use numerical modeling, or a computer model, to undertake a hazard assessment. A map is created where elements can be added, like relevant volcanoes, passenger vessels, and infrastructure. Essentially – what is the hazard, and where might people and things be impacted by it?
They are focused on the Aegean Sea around Greece and Turkey for this part; water transport is critical for islands where air or ground travel is difficult. It is important to consider local conditions, finding information on the vessels in this location and what materials they are made of.
Important aspects are locations like marinas, where filling with pumice would impact the area if boats were unable to get to the land. This answers questions like how could people be impacted, where could people get stranded during an event?
The computer model allows them to digitally simulate a pumice raft and see where it goes using regional ocean currents data. Running many of these gives a good idea of where the pumice might go under different conditions.
Projects like this add to the entire spectrum of how volcanic activity can impact on our lives and systems. One more puzzle piece added to the bigger picture.
