Detection of Diffuse Seafloor Venting Using Structured Light Imaging by Clara J. Smart a Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in Ocean Engineering University of Rhode Island

A systematic detection process capable of locating and quantifying diffuse seafloor venting using remote technology does not currently exist. Such venting is difficult to detect as it is characterized by both low temperature and low flux rates which cannot be distinguished using current remote acoustic or chemical sensors. Therefore the lack of understanding with regard to the distribution of active sites prevents a good estimation of the contribution of diffuse flow to thermal and chemical patterns within the broader ocean system. Data collected over active vent fields have indicated that a structured light laser sensor, also used for high resolution seafloor bathymetric mapping, has the ability to detect near bottom temperature anomalies. Over areas of venting, changes in the index of refraction cause the projected laser line to appear blurred. To isolate and quantify this phenomenon image processing algorithms have been developed to detect diffuse venting using laser line images collected during near bottom surveys. This sensor system when mounted on an autonomous or remotely operated vehicle, will allow for large systematic surveys resulting in maps indicating areas of active venting. Analysis of multiple data sets indicates this system is capable of detecting both small point source vents and low temperature diffuse flow. Current analysis is qualitative with future quantitative goals being addressed in relation to the number of factors that contribute to the observed appearance of the laser line. Ultimately, the result of this research will be a map of vent activity over specific survey sites that can be quantitatively analyzed to provide an understanding of the extent and flux associated with diffuse flow sites.