Just last weekend, I went to visit my 4 years-old goddaughter back in Belgium and I was telling the secrets of the oceans, their amazing creatures and how I became a deep-ocean explorer. While I was speaking, I could see the same excitation and admiration in her eyes that I feel every time I get to go at sea. This year again, I have the wonderful opportunity to join an upcoming cruise on board the Celtic Explorer (CE18008). This is the Irish research vessel, run by the Irish Marine Institute (https://www.marine.ie/). The cruise is called TOSCA (Tectonic Ocean Spreading at the Charlie Gibbs Fracture Zone) and we will sail on the 14th of May towards the Charlie-Gibbs Fracture Zone.
Alright… If you’re not familiar with the seafloor topography, you probably don’t know where it is. So, a fracture zone is what we call a transform fault which will connect two segments of a spreading ridge (remember your lectures of tectonic plates?). In this case, the Charlie-Gibbs Fracture Zone connects the Reykjanes Ridge (the same one dividing Iceland in two halves) and the Mid-Atlantic Ridge, and crosses the deep-sea basin of the North-Atlantic about 50 degrees North, from Ireland to Newfoundland. Now you should be able to point out its location on the GEBCO map !
The purpose of this cruise is to improve our understanding of tectonic plates at divergent plate boundaries, like processes such as the effects of change in the magma melt supply at volcanoes, and what features they create, such as exposure of mantle outcrops on the seafloor.. The mantle is essentially made of peridotite and is found below the oceanic crust, but sometimes during the stretching of the crust, the mantle is exhumed, and brings with it a higher heat gradient. We call these phenomena oceanic core complexes (OCC).
So what are we going to do there? A bunch of things! We will map the seafloor with a multibeam swath sonar, we will undertake some seismic reflection geophysics surveys, and at the same time, acquire some sub-bottom acoustic profiles to understand the sediment cover infilling the troughs. We will also collect sediment by gravity coring to learn about mass wasting (rapid transport of sediments) and do some dredging (a metallic net pulled by the back of the ship scrapping the seafloor surface). Finally we will explore for hydrothermal plumes with CTD casts which will measure Eh, nephels and CH4, and dive with a ROV (remotely operated vehicle) to sample seafloor outcrops or mineral deposits and vent fluids if we locate some hydrothermal vents! Hydrothermal vents are very often associated to oceanic core complexes. This is a similar case to the Von Damn Field on the Mid-Cayman trough that you have learned about in the Week 1 ! (Ok, I’ll tell you, I am most excited about finding hydrothermal vents!)
All of this is exciting, isn’t it? If you would like to hear week by week the news of the CE18008 expedition, then stay tuned on the blog and I’ll post some updates, and my colleagues on the ship will post few more as well on the official cruise blog ! By the way, this link has as well many other posts about other cruises of any different kinds: fisheries, ocean climate on the Irish Sea, micro-plastic … Check them out :-).
PS: With my niece, we drawn some fine art on polystyrene cups, and hop direction to few thousands meters depth for an original souvenir !