Reasons for taking core samples

In response to questions asked by Otumoetai Intermediate School students, expedition Co-chief Scientist Dr Demian Saffer shows how sediment and rock in a core sample change as the drill goes down deeper and deeper. Geologists on board the research ship JOIDES Resolution take small geological samples back to their home laboratories for further study.

Note: This video footage was bounced off a satellite during a Skype session on board the ship. The beeping in the background is the cryomagnetometer – learn more about this specialised lab machine in the video What do core samples tell us?

If you find the sound quality difficult, please refer to the transcript.

Transcript

DR DEMIAN SAFFER

One of the main reasons that we collect the core to begin with and then split it open is for scientists to describe the materials. These are three different pieces of core that are from different depths in the borehole. The one on the right-hand side is from about 200 metres into the borehole. The one in the middle is about 150 metres below that, and you can see there’s a change to the kind of rock that we have. And then, on the left-hand side is actually from close to the bottom of the borehole and about a kilometre below the seafloor.

So one of the things we want to do is understand the different types of rocks that are actually being moved – kind of like a conveyor belt – into the subduction zone, into the Hikurangi slow slip region, to try to understand a little bit about what are the rock types and if there is something special about the rocks or the layering of the rocks or the strength, the mechanical properties of the rocks that might explain why we have earthquakes or why we have slow slip events along this fault line.

You will notice that there all these little pieces of Styrofoam in the cores, and of course, the Styrofoam wasn’t there when we collected it, that didn’t come out of the Earth, right. The Styrofoam is there because those are little places where scientists on the ship have taken out samples and then taken them home to laboratories to do detailed analyses, measure the chemistry or the size of the particles in the sediments or the physical properties of the rock – so things like the strength or how easily the rock may slide past itself if it were going to say try to have an earthquake, what the stresses would be working on it if it was going to break by sliding.

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 High-resolution close-up footage of cores by Thanos Fatouros for IODP courtesy of Thanos Fatouros, US Science Support Program and IODP All other footage from ship to shore video conference from JOIDES Resolution expedition #375 courtesy of Otumoetai Intermediate School