the continental slope down to the deep sea. The canyons are usually (but not always) linked to major river mouths across the continental shelf, and provide a chute for the sediment spewed out by rivers. Water depth on the continental slope can reach thousands of metres within a few kilometres of the shelf break. The continental rise At the base of the continental slope, the gradient becomes shallower. The area between the continental slope and the abyssal plain (the deepest part of an ocean basin) is called the continental rise . Here, sediment which has moved down from the continental shelf piles up at the base of the slope, and is gently sculpted by slow-moving currents which travel along the contours of the slope break. On passive continental margins, the continental rise tends to mark the transition between continental cruse and oceanic crust. The abyssal plain The abyssal plains are the deepest regions of the ocean basins (with the exception of subduction trenches), and they form vast expanses of flat, cold, dark terrain. Here, the water can reach depths of over 5000 metres, so little or no light penetrates into the murky depths. If the ocean basin is split by a mid-ocean spreading ridge (for example, the Mid Atlantic Ridge in the Atlantic Ocean), the seafloor will start to gently rise upwards again as you approach the spreading ridge. This is because of the thermal buoyancy of the ocean crust around the hot spreading centre. As you move away from