Final answer:
The deepest parts of the oceans are the trenches, with the Mariana Trench being the most profound, housing the Challenger Deep. These geological features are associated with convergent plate boundaries where subduction occurs. Trenches are narrower and more elongated compared to the expansive abyssal zone.
Step-by-step explanation:
The deepest parts of the oceans are the trenches. Trenches are topographic depressions of the sea floor, which are generally narrow but very long. These geological formations are commonly associated with convergent plate boundaries, where one tectonic plate subducts beneath another, leading to the creation of these profound features. An example of such a trench is the Mariana Trench located in the western Pacific Ocean, which includes the Challenger Deep, the deepest known point in Earth's oceans.
Rift zones, such as the Mid-Atlantic Ridge, are places where new crust is formed as tectonic plates pull apart from each other, but these are not as deep as trenches. Conversely, subduction zones are locations where old crust is destroyed as it plunges into the mantle beneath an overriding plate, which can form the deepest parts of the oceans. The absolute deepest zone, the abyssal zone, extends to depths of 4000 meters or greater but is broader and more encompassing than the discretely narrow and elongated trenches.