Mapping of the ocean floor is called bathymetry. The figures are usually in minus number with zero being the sea surface. The larger the number the deeper the ocean floor. There are many ways to collect data about the depth of ocean floor. Satellites, gravity, echo sounders, seismics are probably the most obvious. As ships travel around the world many voluntarily contribute to GEBCO – General Bathymetry Chart of Oceans. This organisation takes the ships echo sounder tracks and compiles the data. Geomapapp.org is a great resource for anyone interested in ocean mapping. The map on the left (above) looks really good, we can definitely see clear mountains and valleys. Each pixel in this map is 50m – look at the scale line – 10km. You can see a small section has been blown up – this is about 2000m – you can’t see very much. Think of walking for about 25 minutes, think of all the buildings you would pass, the ground you cover – that’s the same as one end of this square to the other. Scientists are missing all that information. That is where Autosub comes in. The same information has been plotted by Geraud with information taken by Autosub. Each pixel is 4m. Can you see the orange round circle shaped objects? These are volcanoes about 200m across and 50m high. All missed on the previous scale. If we are to understand the workings of our planet, if we are ever to understand how plates interact it is vital that we have such information. These volcanoes are probably older than the Ocean Core Complex – OCC (the red area to the West of the box on the main map), this is unusual as the volcanoes are closer to the ridge and therefore expected to be younger. The volcanoes could be a legacy of previous magmatic spreading? If so why did that spreading stop? Will is start again? Is the spreading now solely the OCC (detachment fault) rising out of the crust? There is a great deal of data to analyse. The scientists are working together (Durham, Birmingham and Cardiff Universities) to research and understand the data so that they can better understand how the world’s longest mountain chain and volcanically active ridge works.
Think about how medical scans, mobile phones, computers have developed over the last 20 years or so. It is the same with ocean floor survey data. Scientists are getting a clearer picture all the time and as a result greater understanding of our planet.
Above are multi beam images of the seafloor. The topmost image is from early multi beam data, the middle image is from a ship and the bottom image is from a deep towed multi beam. Each box is 2 square kilometres. This is also the Mid Atlantic Ridge but slightly further North than our research 45 degrees. This expedition is at 13 degrees North. Again you can clearly see how vital it is to have detailed images to have a clear picture of what the bathymetry is actually like.
This is a map created from satellite data of the approximate area of ocean that we are studying. Whilst it is useful it is not of the detail needed for our research. That said, I know that in the early days when these maps first were produced scientists found them a ‘revelation’.
A world bathymetric map.
The streamer came back in today along with guns. That part of our survey is over.
Autosub has been deployed again to gather more data. One of the biggest problems for Autosub is overcoming the corrosive salt water – even stainless steel corrodes under these conditions.
The Ocean Bottom Seismics are starting to come back in. I find it amazing that that they have been @3000m down on a rocky sea floor under high pressure in saline conditions and they come back to the scientists. Real skill and detailed planning in evidence. Do see Christine’s terrific blog for more detail: obsatsea.wordpress.com
Nigel with the retrieved airguns in the background. He likes his house.
Finally: Declan sends his very best wishes to MATTHEW 🙂