The Japan Deep Sea Impact Experiment (JET) created a near Seafloor sediment plume in an attempt to reproduce conditions during manganese nodule mining in the Clarion-Clipperton zones in 1994. An image analysis technique of seafloor photos is developed for quantification of resedimentation of the plume. Colour differences between the nodules, black, and the sediments, light ocher, are used in the technique. A laboratory water tank test for calibration of the resedimentation is introduced. The colour changes, from black to light ocher of the nodules, in deep-sea photos observed after the resedimentation are analyzed by the technique. An example contour map of thickness of the resedimentation is presented.
During manganese nodule mining in the deep ocean, a large amount of deep-sea sediment is recovered by the collector with the nodules. Most of the recovered sediments are separated from the nodules and discharged from the collector immediately. They resuspend and make a sediment plume near the seafloor. Environmental impact research for manganese nodule mining was initiated in 1989 in Japan. The objective is to establish an effective environmental assessment method and to do develop some guidelines for prevention of mining pollution. Following five years of planning and base line studies of the environment in the Japanese mining claim the Japan Deep Sea Impact Experiment (JET) was conducted in 1994. The JET involved the creation of artificial impacts to the environment of a pre-evaluated area in the claim. Post experiment evaluation was carried out in order 10 assess the environmental impacts (Fukushima, 1995). In order to simulate the impacts of future manganese nodule Mining, the JET created a near seafloor sediment plume (Barnett and Yamauchi, 1995). The plume dispersion and resedimentation were measured by 12 mooring systems deployed in the area (Fukushima, 1995).
