On Tuesday, August 11th, we departed the harbor to explore seeps in Palos Verdes and Redondo Knoll located near the San Pedro area. Multibeam mapping and subbottom sonar data was collected for both sites. For those who are not aware, multibeam is a type of sonar that emits sound waves in a fan shape beneath the ship’s hull (Figure 1). The amount of time it takes for the sound waves to bounce off the water bottom and return to a receiver is used to determine water depth (Figure 1).
Figure 1. Visualization of how multibeam bathymetry is collected (source: NOAA)
The subbottom sonar emits sound waves at a lower frequency, which allows for the wave to penetrate below the seabed creating a image of structural layers that are hidden from view (Figure 2).
Figure 2. Example showing subbottom profiling, NOT from Nautilus, but from another source (Source: http://www.affiliatedresearchers.com).
Multibeam mapping and subbottom profiling continued until Tuesday morning, August 12th.