Getting Under the Earth's Surface

Tracking the movement of the Earth's tectonic plates is not easy.

As we move further back in time, there are fewer clues about how the plates have moved on the Earth's surface. Creating a model of the entire planet requires hundreds of millions of calculations for each moment in time.

It's a task Cardiff University's School of Earth and Ocean Sciences has only been able to contemplate with the help of High Performance Computing.

Over the past two years, a PhD project at the School has tried to work out how the Earth has worked as a body for the past 300 Million years. Supervised by Dr Huw Davies, the Universities of Utrecht and Lausanne are also involved along with a major international company.

The modelling work is based on concepts of mantle convection – movement in the layer of flowing rock beneath the Earth's crust. Convection is a key factor in the movement of the tectonic plates making up the surface.

Dr Davies said: "We utilise what are effectively equations for convection – how this very stiff fluid moves. Our starting point is before 300 Million years ago when we know very little about the Earth. We apply these notions together with our understanding of plate motion histories and run the model forward to the present day. We can then compare the results with seismic tomography imaging of how Earth's interior actually looks today. Agreement and disagreement between the two shows up strengths and weaknesses in the model."

However, all this requires a lot of computing power. The model of the Earth is made up of 100 million different information points, each with five variables at each point in time. Each simulation is run for 10,000 to 100,000 timesteps. This is where Cardiff's High Performance Computer, Merlin, run by Advanced Research Computing @ Cardiff (ARCCA), comes in.

Dr Davies: "The computational runs can vary in scale. However the highest resolution models can take up a quarter of the machine's power for many tens of hours.

"Up until recently we couldn't really recreate what's going on inside the Earth. It's not exactly the sort of thing you can do in a lab. Our project is still on-going, but now we have the computer power to let us run models and test what might be going on."

Advanced Research Computing @Cardiff (ARCCA) provides high performance and high throughput computing services to support research at Cardiff University. This includes running the powerful "Merlin" Supercomputer (a 2048 core Intel Harpertown Linux cluster) and "Condor", a system which capitalises on unused PCs across the University's campus. ARCCA also provides training courses tailored to the researchers' needs from introductory training through to advanced programming and software development techniques. ARCCA will complement HPC Wales, helping to grow the community of users and identify new opportunities.