Drilling into the Depths of the Bengal Fan
Preparations are underway at our third and deepest site. Our target depth is 1500 meters below the seafloor, which is made even more challenging by the fact that the seafloor is 3600 meters below the ship!
To help us reach our target, we decided to install a re-entry system. So for the past two days, we were busy assembling and lowering 400 meters of casing – hollow metal pipe about 11 inches in diameter. This casing was drilled into the seafloor to help stabilize the upper part of the hole, essentially by preventing the sediments from caving in. After the casing was in place, we pulled up the drilling assembly and then lowered a different drilling system that will allow us to collect cores.
But can you imagine how we would get the drill string back into that hole? Remember that it’s less than a foot wide and over 3.5 kilometers deep. Someone once made the analogy that this is like standing on the top of the Empire State Building with a long string of spaghetti and trying to get the end into an espresso cup!
Luckily, the casing is attached to a large painted cone that sits on the bottom of the seafloor. With the help of an underwater camera system, and the incredible skill of our Captain and Dynamic Positioning Operator, we successfully re-entered the hole early this morning. We have started drilling deeper and should have core on deck within the next few hours.
It will be almost two weeks before we get to 1500 meters. But why go through all this trouble to drill this deep? We want to recover older sediments – and by older I mean about 40 million years old! Sediments of this age might have come from the early stages of erosion of the Himalayas and represent the beginning of deposition of the Bengal Fan. The composition and characteristics of these sediments will provide clues about the collision of India with Asia, the resulting uplift of the Himalayas, and the development of the Asian monsoon.