<P> The Hawaiian--Emperor seamount chain is a mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii . It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, and the Emperor Seamounts: together they form a vast underwater mountain region of islands and intervening seamounts, atolls, shallows, banks and reefs along a line trending southeast to northwest beneath the northern Pacific Ocean . The seamount chain, containing over 80 identified undersea volcanoes, stretches over 5,800 kilometres (3,600 mi) from the Aleutian Trench in the far northwest Pacific to the Loʻihi seamount, the youngest volcano in the chain, which lies about 35 kilometres (22 mi) southeast of the Island of Hawaiʻi . </P> <P> The chain can be divided into three subsections . The first, the Hawaiian archipelago (also known as the Windward isles), consists of the islands comprising the U.S. state of Hawaii . As it is the closest to the hotspot, this volcanically active region is the youngest part of the chain, with ages ranging from 400,000 years to 5.1 million years . The island of Hawai ʻi is composed of five volcanoes, of which three (Kilauea, Mauna Loa, and Hualalai) are still active . Lō ʻihi Seamount continues to grow offshore, and is the only known volcano in the chain in the submarine pre-shield stage . </P> <P> The second part of the chain is composed of the Northwestern Hawaiian Islands, collectively referred to as the Leeward isles, the constituents of which are between 7.2 and 27.7 million years in age . Erosion has long since overtaken volcanic activity at these islands, and most of them are atolls, atoll islands, and extinct islands . They contain many of the most northerly atolls in the world; one of them, Kure Atoll, is the northernmost atoll in the world . On June 15, 2006, U.S. President George W. Bush issued a proclamation creating Papahānaumokuākea Marine National Monument under the Antiquities Act of 1906 . The national monument, meant to protect the biodiversity of the Hawaiian isles, encompasses all of the northern isles, and is one of the largest such protected areas in the world . The proclamation limits tourism to the area, and calls for a phase - out of fishing by 2011 . </P> <P> The oldest and most heavily eroded part of the chain are the Emperor seamounts, which are 39 to 85 million years in age . The Emperor and Hawaiian chains form an angle of about 120 ° . This bend was long attributed to a relatively sudden change of 60 ° in the direction of plate motion, but research conducted in 2003 suggests that it was the movement of the hotspot itself that caused the bend . The issue is still currently under debate . All of the volcanoes in this part of the chain have long since subsided below sea level, becoming seamounts and guyots (see also the seamount and guyot stages of Hawaiian volcanism). Many of the volcanoes are named after former emperors of Japan . The seamount chain extends to the West Pacific, and terminates at the Kuril--Kamchatka Trench, a subduction zone at the border of Russia . </P>

The age of volcanic islands formed over a hot spot