Harrow and Hillingdon Geological Society
Ocean Drilling - a Journey to the South Atlantic
If all the presentations for the New Year are as good as this one we will be extremely lucky. This talk was a power-point presentation and the speaker was able to utilise all the facets of the computer technology very well. Since the voyage of HMS Challenger in 1872 a large number of investigations had been done, throughout the 20th centure, to examine the composition of the oceanic floor, mineral deposits, temperature or topography.
In 1968 work was recommenced and by 2003 more than 1200 cores had been examined. The purpose of this expedition, which started in Rio de Janerio was to determine if core samples collected at Walvis Ridge off the west coast of Africa, would help unravel previous patterns of global warming. The actual collection and manipulation of the cores was quite a delicate procedure, each sample of 1.5 metre length, being divide into two halves, one for current examination, the other for future reference. There were hundreds of lab samples to be examined, just in Palaeontology.
It was apparent from data shown that there had been global cooling over the last 50 million years but over the last 25 million years CO2 concentrations were low and can't be responsible for the cooling. Possibly the most significant investigation was that of the gas hydrates which are widespread throughout the world. They are methane in nature and obviously associated with organic deposits. These gas hydrates are unstable at warm temperature and low pressure. CH4 has 62 times more heating effect than CO2, and dissociates to form more CO2 and water thereby reducing the pH of the ocean. These data are highly significant because by destabilizing the gas hydrates a runaway “greenhouse” effect will occur. In passing it was also suggested that an alteration in pressure could liberate gas hydrates, which could explain the effects known as the Bermuda triangle.
The Paleocene-Eocene event is assumed to be associated with a massive dissociation of gas hydrates. These led to a short-lived global warming in the ocean and atmosphere, a mass extinction of organisms in the sea and changes in the species on land.
We were shown slides of the crew, the port area and the research vessel itself including the labs. It was apparent that everyone was kept extremely busy and that peace and quiet was at a premium. There were masses of statistics, which I found a little difficult to absorb but overall it was a really interesting talk and no one could fault the speaker for her enthusiasm.