Geology Pacific Plate

Geology
Main article: Pacific Plate
The Pacific is ringed by many volcanoes and oceanic trenches

The andesite line is the most significant regional distinction in the Pacific. It separates the deeper, mafic igneous rock of the Central Pacific Basin from the partially submerged continental areas of felsic igneous rock on its margins. The andesite line follows the western edge of the islands off California and passes south of the Aleutian arc, along the eastern edge of the Kamchatka Peninsula, the Kuril Islands, Japan, the Mariana Islands, the Solomon Islands, and New Zealand's North Island.

The dissimilarity continues northeastward along the western edge of the Andes Cordillera along South America to Mexico, returning then to the islands off California. Indonesia, the Philippines, Japan, New Guinea, and New Zealand lie outside the Andesite Line.

The Pacific Ocean takes up roughly one third of the Earth's surface, having an area of 179.7 million square kilometres. It contains about 25,000 islands (more than the total number in the rest of the world's oceans combined), the majority of which are found south of the equator, Including partially submerged islands. The ocean was mapped by a man named Abraham Ortelius, he called it Maris Pacifici because of Ferdinand Magellan, who sailed the Pacific during his circumnavigation from 1519 to 1522 and said that it was much more calm than the Atlantic.

The Pacific Ocean has several long seamount chains (which are chains of mountains submerging from the ocean seafloor) formed by hotspot volcanism. "The Ring of Fire" is the world's largest belt of explosive volcanism. It is named after the several hundred active volcanoes that sit above the various subduction zones(which is a geological process in which one edge of a crustal plate is forced sideways and downward into the mantle below another plate).

Within the closed loop of the Andesite Line are most of the deep troughs, submerged volcanic mountains, and oceanic volcanic islands that characterize the Pacific basin. Here basaltic lavas gently flow out of rifts to build huge dome-shaped volcanic mountains whose eroded summits form island arcs, chains, and clusters. Outside the Andesite Line, volcanism is of the explosive type, and the Pacific Ring of Fire is the world's foremost belt of explosive volcanism. The Ring of Fire is named after the several hundred active volcanoes that sit above the various subduction zones.