July 30, 2007
Location: Labrador Sea, The Makkovik Margin
We are over the Makkovik Margin, having arrived last night close to midnight. Ian and Steve from the University of New Brunswick are mapping the sea floor here with the multi beam scanner. The multi beam has a sounding device which emits an electrical impulse with a frequency of 30, we are unable to hear it on board. The lower the frequency the greater the penetration it will have in the sea floor. When the sound or pulse rebounds off the bottom, it hits a receiving element which vibrates.
Ian and Steve use 4 computers to interpret the vibrations which are translated into maps. A 3 dimensional map is continuously updated as the sound returns from the sea floor and an inset shows grey lines which record the level of intensity of the returning sound. Another screen shows a small diamond shape representing the ship and our course. We have been traveling back and forth across the area for 14 hours and will continue to do so for almost 6 more. Each pass of the boat expands the range of the map.
The 135 beams pickup electrical impulses returning from a range of 4,000 to 6,000 feet. Every pass helps Ian and Steve fill in another strip of the map. One of the maps on their screens resembles a painting being made in super slow motion, a series of grey brush strokes are already on the screen and another one is being painted on as I watch. It's fascinating to actually be seeing what we are passing over, 2003 meters below!