The three major ocean basins have distinctive characteristic seafloor features: the Pacific Ocean is famously encircled by a near-continuous ring of deep subduction trenches (the Ring of Fire), including the Mariana Trench (the deepest point on Earth), reflecting its margins being dominated by convergent (subducting) plate boundaries, whereas the Atlantic Ocean is characterized primarily by a prominent mid-ocean ridge system (the Mid-Atlantic Ridge) with comparatively few trenches, and the Indian Ocean, while also possessing a significant mid-ocean ridge system, does not have the single longest mid-ocean ridge among the world's oceans.