Field work done... for now!

Yesterday was our last day in the field :(

It was another belter of a day, and Carlos and I drove about looking for sections further away from the volcano. All the sections we have so far from this trip are close together (within about 5km), as are the majority of all the sections previously described by Carlos, Ivan and Jim. Jim Luhr carried our some of the very first work on Volcan de Colima in 1980. Carlos and Ivan have been continuing his work, and my project is a continuation of his work.

It's good to have sections close together for correlation of the units, but when it comes to working out the volume of the eruption, you need to have a good distribution of samples from units across a big an area. The more distal sections will have smaller pumice and lithic sizes, and should be thinner deposits. However, it all depends on the direction of the wind, the strength of the wind and the topography. If there is a strong wind at the time of eruption, the pumice and ash will be carried much farther, forming thinner deposits over a greater area. Pumice and ash fall from an eruption will generally give pretty even coverage over the topographic highs and lows, as it 'rains' out the sky, whereas pyroclastic flows travel at speeds of well over 100km/hour crossing valleys and climbing up over highs of over 1000m, will leave thicker deposits in valleys and thin deposits on topographic highs. It makes it very difficult to correlate pyroclasitc flow deposits across an area, because the thickness can vary enormously over short distances. Hence sifting through ash looking for charcoal! It makes it a lot easier to correlate if we have matching dates!

We found some good sections, some with charcoal. Those without charcoal, I hope to be able to correlate with other units by doing a comparison of their mineralogy and geochemistry. We'll see...

Carlos and I got a bit fed up sitting in the truck, so decided to walk along a track to find a section. We ended up walking 8km, found a good section and took some photos...

While we were walking I asked Carlos about how he came to study volcanology. He had a bit of a detour in Marine Geology too!

So it was back picking out charcoal this morning and sieving pumice this afternoon...