It includes underwater mountains and ridges and extremely deep areas called trenches. A great underwater mountain range extends from north of Antarctica to North America off Mexico. Volcanic eruptions on the ridge have produced a number of peaks, some of which form islands. The deepest parts of the Pacific Ocean are near the shores. They include the Japan and Kuril trenches, which border island chains of the western Pacific.
Trenches also lie near the Aleutian Islands and off the coast of Central and South America.
The Mariana Trench, near Guam, includes the Challenger Deep, the deepest known spot in any ocean. Structures called hot vents, or hydrothermal vents, are located primarily in the eastern Pacific. These hot vents occur as a result of ocean water seeping down through cracks in the ocean bottom and being heated by underlying volcanic molten rock. A continental shelf extends off the shore of each continent bordering the Pacific. The shelves along North and South America are fairly narrow, but the shelves along Asia and Australia are broad.