The Pacific Realm is, of course, a very large place. Its great size is, perhaps, its most important geographical feature. The land area of the Pacific Realm is made up of a large number of islands that have very small (relatively speaking) land areas. In between these islands are vast stretches of ocean. This has been important geographically because it has caused many of the islands of the Pacific Realm to be relatively isolated from one another and from the outside world. This has caused there to be few animals that natives of the islands could exploit. It caused there to be a broad variety of cultures and languages in the realm.
Geologically speaking, the major feature of the Pacific Realm is volcanism. Much of the land of the Pacific Realm owes its existence to volcanism. The Hawaiian Islands are one example of this. Even the islands like New Zealand and Indonesia which are parts of continental land masses have a great deal of volcanic activity because of the nature of the plate tectonics of the Ring of Fire. Therefore, volcanism is the major geological feature that is common to most parts of the Pacific Realm.