Day 4: Sampling our first seamounts!

By Jamie Menzies

After a two and a half day transit, the RV Investigator arrived at the first sampling site, a seamount called Frederick’s Reef.

First, a multibeam sonar was used to make a detailed map of the seafloor. The sonar works by listening for echoes made when sound waves hit objects on the seafloor. This information was used to create a map which allowed scientists to choose the best site to sample.

Next, a dredge – a kind of shovel used to remove material from the seabed – was lowered 2000 metres into the water onto the side of the volcano. The dredge was slowly manoeuvred in order to scoop up some of the rocks the scientists were interested in.

The rocks and sediment were laid out on deck for a first look by excited scientists and then were brought into the lab for further identification, photography and documentation.

This particular sample site produced a lot of limestones, which are sedimentary rocks made of fossil fragments. The seamount was sampled in two further locations which gave us lots of nice igneous rocks formed by the volcanism. Both of these rock types are useful to understand the volcanic processes and to calculate the age of the seamount.