Drilling for core samples

Science communicator and educator Aliki Weststrate explains how core samples are obtained from the seafloor. She also tells us why it is safe to drill into earthquake zones.

Jargon alert: A moonpool is an opening in the base of a ship or the floor of a platform giving access to the water below.

Note: The video is part of a ship to shore Skype interview with Otumoetai Intermediate School. The video footage was bounced off a satellite, which affects the sound and picture quality.

Transcript

ALIKI WESTSTRATE

There’s the JOIDES Resolution, and the derrick or the drill tower is in the middle – that’s 60 metres high. That’s got a drill pipe running down through the centre of it, down through a moonpool. So the drill pipe goes down the bottom of the ship, down through the water, down to the seabed and then it can drill down as deep as 2 kilometres under the seafloor.

We actually add drill pipe on as we go deeper, and they’re 40 metres long. So we add them on the ship, we add them on the drill rig floor – we attach them and then we push them down deeper. It is kind of like adding straws together and pushing them into your milkshake.

And how long it takes to get a core is … that really depends on how deep the seawater is and how deep we are going under the seabed. So where we were at our last site, we had 3 kilometres of water, it was really deep, and then we were going down a kilometre below the seabed as well. It would take 3 hours for the drill string to go down through the moonpool, down pushing this plastic pipe down into the mud and the sand below, and then pushing it in and collecting it and pulling it back up would take about 3 hours for just one trip.

And that would bring up 40 metres of a long plastic pipe full of mud and rock and sediment.

The ship has drilled into lots of earthquake zones all around the world for about 40 years. It’s never triggered an earthquake. The drill pipe is actually only 30 centimetres across and it doesn’t go in very deep. It doesn’t have enough energy to set off the seismic energy that’s required to trigger an earthquake, so it doesn’t create enough pressure to set off an earthquake, even a small earthquake.

Acknowledgements Dr Demian Saffer, Pennsylvania State University Aliki Weststrate International Ocean Discovery Program (IODP) Australia and New Zealand International Ocean Discovery Program Consortium (ANZIC) GNS Science Otumoetai Intermediate School

Animation of derrick tower and coring operation below JOIDES Resolution created by Thanos Fatouros for IODP courtesy of Thanos Fatouros, US Science Support Program and IODP

Footage of onboard drilling operation, extraction of cores and time lapse of derrick tower and drilling on JOIDES Resolution expedition #342 created by Science Media for IODP courtesy of Science Media, US Science Support Program and IODP

Underwater camera footage by Aliki Weststrate for IODP courtesy of Aliki Weststrate, ANZIC and IODP

Map of drilling sites across Earth, IODP and JOIDES Resolution Science Operator

All other footage from ship to shore video conference from JOIDES Resolution expedition #375 courtesy of Otumoetai Intermediate School