Monday, October 22, 2012

Taking a drill core

Yesterday we started our research at our first site in the island of Yap.  We drilled a core from a medium-sized colony of Porites coral, shown in the picture.  We use an underwater hydraulic drill run by a motor on the boat that forces seawater down a hose and through the drill head that turns the bit.  The drill bit is like a hollow tube that cuts a circle down around a central core of coral skeleton.  When the bit has drilled all the way down its full length (80 cm or about 32 in), we pull it out and push a tool like a spear tip down the hole to break the core loose.  Then we use a final tool, also a hollow tube with little 'grabber' teeth, to reach into the hole and pull out the core.  We add extension rods to the drill bit, breaker and grabber, and drill sections of core like this until we reach the bottom of the coral. 

Today we're traveling to our second site, Woleai Atoll.  Our colleagues in Yap have radioed ahead to let the villagers know we are coming, and we hope to arrive early enough to meet them tomorrow evening.  The villagers are skilled fishermen with detailed knowledge about the coral reefs around their island, and we will ask them to help us locate giant corals either inside the lagoon or on the outer reef.  Such local knowledge can save us days of searching and be critical to our success. 


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