JC010: Mud volcanoes and submarine canyons


 JC10



The ROV Isis...in action!

The ROV at work – recovering the elevator

 

Sometimes an experiment needs to be left for days, or even years, on the bottom of the seabed.  When this is the case a special elevator platform is taken down to the sea then used to return the apparatus to the surface.

This is the experimental equipment that Rachael lowered into place a couple of days ago to study the carbon cycles in the deep sea.  The equipment at the bottom of the picture are cores on the ROV that will collected after the apparatus has been picked up.

The ROV manoeuvres into position. The orange containers are plastic protection around large glass air-filled containers. They are the buoyancy aids that will eventually lift the apparatus back to the surface. Glass is used as it is very strong under compression (squashing). The pressure of the water 3.5km under water is about 350 atmospheres which is about 88 times more pressure than when you swim in the deep end of a swimming pool and go so deep your ears hurt. At this pressure even 15mm thick glass is very fragile and can easily break.

Here the ROV moves in to pick up the experimental equipment using one of its arms grabbing the handle on the top...got it!

The experiment is picked up by the ROV and carefully placed on a platform.  It is this platform that is called the elevator, as it will go up to the surface. The platform has space for two sets of experimental equipment so once one is in place the ROV goes off and collects the other set of experimental equipment. Now both have to be fastened into place.

Metal brackets are lowered into place.  They are held firm by very strong elastic cords which the ROV carefully has to hook over a bar at the base of the platform.

Now the ROV secures the other equipment until all four brackets are securely fastened.  The elevator is now ready to be sent to the top.

Next the ROV manovers to removes the heavy iron weights that keep the elevator on the bottom.  This makes the Elevator lighter but not yet quite light enough to rise. Next a buoyant rope is released.  This is for the crew to grab when the Elevator reaches the surface.

Before the elevator is released the ROV Team must first move the ROV out of the way then contact the Bridge to let them know they are about to release and advise the bridge if they think the ship needs to move out of the way (they don’t want the Elevator to pop up under the ship).  When all is safe then an acoustic signal is sent to the ROV causing the remaining iron weights to be dropped and the ROV starts rising. 

That is if it hasn’t got stuck in the mud.  If it is stuck in the mud the ROV very carefully manoeuvres closer and lifts the section that is stuck freeing the platform to rise.


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