A 42-year-old converted oil exploration ship, JOIDES Resolution is one of the few drilling vessels available to earth scientists for the geological study of the seabed at ocean depths below 8,000 metres. Its ultimate aim is to become better acquainted with what goes on beneath the Earth’s crust.
Scientific ocean drilling took off in the late 1950s and early 1960s with Project Mohole, a United States attempt to drill to the base of the Earth crust.
Project Mohole was to be Earth sciences’ answer to the space program – an attempt to retrieve a sample of the Earth’s mantle by drilling a hole through the Earth’s crust to the “Moho” or Mohorovičić discontinuity, which lies between the two layers.
One clear advantage of drilling into the oceanic crust is that it is a mere 7 kilometres, compared to that on land which is many times thicker.
But the project didn’t even get close to its goal, only reaching down 183 metres (601 feet) below the seabed.
JOIDES Resolution Oceanic Floor Drilling
The first drilling expedition under the Joint Oceanographic Institutions Deep Earth Sampling (JOIDES) program goes back to spring 1965 to the Blake Plateau off the southeastern United States.
Currently sailing under the flag of Cyprus, the JOIDES Resolution has a carrying capacity of 5500 t DWT (Dead Weight Tonnage).
Her length overall (LOA) is 143.29 metres (470 feet). Her width is 21.34 metres. Her current draught is reported to be 7.6 metres. The ship is 62 metres (202 feet) tall from the ocean surface to the top of the derrick.
The derrick on the JOIDES Resolution is 45 metre-high and allows 30 metres of forage stalks to be operated simultaneously.
Drilling takes place all hours, with 9.5-metre long core samples hauled to the surface for immediate analysis. Cores are then split in their length and stored in a refrigerator.
The video link below shows a 3D VR model of how the Advanced Piston Corer (APC) is operated, and the soft sediments are retrieved from the deep ocean floor, using the drilling technology on board the JOIDES Resolution.
It’s well worth a watch if you want to understand more about the coring process…
The drill pipe hangs from the top of the derrick, passes through a hole in the ship’s hull, into the ocean and all the way down to the seafloor. Each section is 30 metres in length.
The drill heads have a limited lifespan before the cutting bits and bearings are worn away. Some drill bits are made of carbon steel, others are impregnated with diamonds. The larger ones are rotary.
The expertise of the drilling crew is essential when it comes to deciding when the point has come to stop drilling.
At such depths, the temperatures and pressures are very high. Every time the pipe is pulled out to change the bit, the hole seals itself back up.
If drilling is pushed until the drill head breaks up inside the hole, it becomes impossible to drill any deeper. And the forage hole has to be abandoned.
The Moon Pool
The moon pool is the large aperture at the centre of the ship that allows the drill string, re-entry cones, and other equipment to pass through to the ocean below.
Quite literally, it is a bottom-less pool – a big opening within the hull of the ship 6.7 metres (22 feet) wide across with heavy doors on the deck side to keep it more or less closed.
Despite this gaping hole, the research vessel remains buoyant, much like an inflated inner tube would.
Water does not enter and flood the ship because the sides of the moon pool extend up inside the ship well above the waterline. In very rough seas, the moon pool doors are closed whenever the ship is moving.
As the sonde is lowered and then pulled back up the equipment can take measurements including
- natural gamma radiation (NGR) from radioactive minerals like uranium, thorium and potassium,
- electrical resistivity (to measure the water or organic material within the rocks), and
- seismic properties (how fast sound waves travel through the rock) which gives information about density.
Other tests can look for faults, folds, bedding planes and other structures which help scientists to correlate the cores that have been brought up and which bits have been lost during the process.
Over the past month, the JOIDES Resolution team of scientists have been sailing the South Pacific Ocean, off New Zealand (IODP Expedition 378: South Pacific Paleogene Climate).
The team drilled down far enough to see evidence of the Paleocene-Eocene Thermal Maximum, a global heating event that occurred approximately 55.5 million years ago.
Ocean drilling has provided evidence of the theory of plate tectonics, revealed the Arctic once had a subtropical climate, discovered frozen methane hydrate, a flammable ice, and found microbial life deep beneath the sea floor.
Past and Future Expeditions
According to MarineTraffic.com, the JOIDES Resolution departed from PAPEETE, PF on 2020-02-08 14:47 LT (UTC -10) and is currently sailing at 9.7 knots with East direction heading to PANAMA CANAL, PA (at the time of writing).
The deepest oceanic floor drilling achieved by the JOIDES Resolution is 1,928 metres (1.2 miles under the sea floor) in the south Pacific during Expedition 317. The deepest the scientific team ever had to send a drill down to reach the sea floor was 5,707 metres (3.6 miles) down. This was Expedition 329.
In studying these rock samples, researchers are probing some of our most longstanding and urgent scientific questions:
- What happened in the wake of the dinosaurs?
- What happens to life when the planet dramatically warms or cools?
- Can millions of years of geological history tell us where we’re heading?