Oceanic trench the level of the surrounding oceanic floor. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of below sea level. Oceanic lithosphere moves into trenches at a global rate of about 3 km/yr. There are approximately of convergent plate margins, mostly around the Pacific Ocean—the reason for the reference “Pacific-type” margin—but they are also in the eastern Indian Ocean, with relatively short convergent margin segments in the Atlantic Ocean and in the Mediterranean Sea. Globally, there are over 50 major ocean trenches covering an area of 1.9 million km or about 0.5%
Trench shield with a shore. While they may serve the same function, trench shoring is a different physical application that holds up the walls of a trench to prevent collapse. In the US, use of a trench shield is governed by OSHA 29 CFR Part 1926.650-.652 Subpart P-Excavations Trench shield Trench shields (also called Trench Boxes or Trench Sheets) are steel or aluminum structures used for protecting utility workers while performing their duties within a trench and avoid cave-ins. They are customarily constructed with sidewalls of varying thicknesses held apart by steel or aluminum spreaders. Spreaders can be interchanged to match the