The EM302 multibeam sonar is capable of achieving large swath widths, of up to 5 times the water depth, which allows the Okeanos Explorer to map entire landscapes at one time. For instance, as seen in the image below, by surveying parallel tracklines over an area, the ship was able to map two adjacent ridges and the pancake-like valley between them. The black lines indicate bathymetric contours 1,000m apart. The ridge on the right rises to 350 meters below the sea surface, making it 3350 meters—or 2 miles—high. Click image for larger view and image credit.
State of the Art Seafloor Survey
Senior Survey Technician
The EM302 multibeam sonar system onboard the Okeanos Explorer is one of the most state of the art systems of its kind available in the world today. Manufactured by Kongsberg in Horten, Norway, the EM302 is capable of detecting features on the seafloor at relative sizes much smaller than have historically been detectable by similar sonars. For example, in 1600 meters of water, Okeanos Explorer’s sonar can detect with sound, or “see”, an object that is 28 meters in length or width. To put this in perspective, it can detect a 9 story building that is one mile away. Another way to imagine this is that with its sonar, the Okeanos Explorer could detect a person who is 5.5 foot tall standing at the opposite end of a 100-yard football field. The idea of detecting these things at these distances is very similar, except we are “looking” down through the volume of the ocean with sound, instead of across the surface of the earth with our eyes.
The EM302 gives us a high resolution “birds eye” view of large areas. What we see underwater is similar to what we see around us every day. In the above image, a panorama of mountains and volcanoes sit majestically near a massive river delta surrounded by a soft sand beach. Since what we see here is actually underwater, there are of course no rivers or river deltas, or mountains and sand bars, but seeing these features makes you wonder how an area like this was formed. Click image for larger view and image credit.
An isolated ridge rimmed by a deeper channel is shown in this bathymetric image. How did this unique geologic feature form? Did the area beneath the ridge sink from the weight of the feature? Or was the channel formed by underwater currents gauging out the softer sediment around the ridge? Further geophysical exploration is necessary to understand such mysteries. Click image for larger view and image credit.
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