A view of the shoreline from the centre of Pitch Lake before and after a downpour. The two photos were taken within moments of each other. We continue with Joanna on her journey through Trinidad as she reaches Pitch Lake: "Days 5 & 6: The source: Pitch Lake and environs Pitch Lake: the reason I’m in Trinidad. Our mission over the next two days is to collect samples both within and around the lake to give us a good strontium signal for this unique region. Of course the other Trinidad/Tobago regions are important too - but this is the core of our study. Cyril and Joanna filling a vial with liquid pitch for contamination experiments We know pitch can ‘contaminate’ the archaeological artefacts that we are studying, including radiocarbon results (a sample of pitch proved to be 44,000 years old, so even a small amount can skew an artefact date, and hence why we were extremely careful with sample processing at the Oxford Radiocarbon Lab). But does it also impact the strontium isotope values of artefacts recovered from the lake? Does a tree growing on the banks of the lake - its roots channelling through pitch deposits - have different values to one growing in the same geological region, but unaffected by pitch? These were some of the questions to which we wanted answers, and why we concentrated our efforts in this area. If we wanted to prove (or, indeed, disprove) that the artefacts recovered from Pitch Lake were made locally, we needed to know what the local signal was. A school group standing on a band of asphalt, below the branches of an Andira sp. tree, from which herbarium and strontium samples were collected. As well as sampling trees in and around the lake, we took some soft pitch samples for contamination experiments. Over the last two years, every visit I have made to the lake was greeted with a downpour - the clouds would momentarily darken and a torrential storm would drench us to the bone. The weeks before had been very dry, and rain was needed, and people began to joke that I was ‘lucky’, having brought the English weather with me - though the ability to bring on rains during the rainy season is a debatable talent. And just as soon as the heavens opened up, the clouds rolled away – and the sun emerged once again. The transition is always blindingly fast. An older house on a pitch outcrop, the front stairs having travelled some distance from the main entrance It’s remarkable how pitch outcrops affect the local environment and villages - such as La Brea. People here quite literally ‘go with the flow’: houses built on the outcrops neighbouring the lake – even those several kilometres away – are susceptible to subsidence. While a house’s front staircase might be in one location, its main entrance may be in another. Building here requires a ‘flexible’ approach. A roadside stall on an outcrop of asphalt, selling fresh breadfruit, avocado and - of course - mango. Of course no trip anywhere in Trinidad would be complete without a mango stop. On our way to the south – including the Icacos, Erin and Palo Seco (the latter two important archaeological sites) – we came across many stalls selling everything from homemade hot sauce to ripe breadfruit, and couldn’t resist stopping for cutlass mangos. It is mango season after all and – I have it on good authority from Yasmin Baksh-Comeau – one of the main reasons for doing fieldwork in the summer.