The Japan Trench is basically Mount Everest turned upside down. Running offshore of northeastern Japan, the trench marks the boundary where the Pacific Plate dives beneath the plate carrying Japan. Scientific drilling has reached water depths exceeding 8,000 meters — roughly 26,000 feet — compared with Everest’s 29,032-foot height. In other words, this scar in the seafloor is nearly mountain-sized in reverse. A viral animation circulating online dramatizes that scale, carving an enormous fissure beside Japan and showing the ocean drawing back as a tsunami builds offshore. The imagery is exaggerated, but the underlying danger is very real. View this post on Instagram At subduction zones, tectonic plates can lock together for decades or centuries while stress builds. When the fault finally slips, the seafloor can move violently, displacing enormous volumes of water.…