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%
Capture of Regina Trench army division), which had been brought from the Belgian coast. On 8 October, attacks by the 1st Canadian Division and the 3rd Canadian Division on Regina Trench, also failed. On 21 October, the 4th Canadian Division attacked the western portion of Regina Trench, as the 18th Division, 25th Division and the 39th Division of II Corps, attacked the part further west (known as Stuff Trench to the British). The Canadians met little opposition and gained the objective, as the II Corps divisions captured Stuff Trench in thirty minutes, giving the British control of the Thiepval Ridge. Three counter-attacks were repulsed