Hawaii | History, Map, Flag, & Facts | Britannica

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The land area of the state of Hawaii consists of the tops of a chain of emerged volcanic mountains that form 8 major islands and 124 islets, stretching in a 1,500-mile (2,400-km) crescent from Kure Island in the west to the island of Hawaii in the east. The eight major islands at the eastern end of the chain are, from west to east, Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe, Maui, and Hawaii. Each volcanic mountain formed during the transit of the Pacific Plate across a hotspot (a region of Earth’s upper mantle that upwells to melt through the crust) located beneath the central Pacific Ocean, and erupting magma added mass to the crust above.

The origin of Hawaii’s islands, islets, and seamounts can be traced to at least 70 million years ago, near the end of the Cretaceous Period (145 million to 66 million years ago). Volcanic activity has become dormant, with the exception of the emergent volcanoes of Mauna Loa, Kilauea, and the Lō‘ihi Seamount. Mauna Loa and Kilauea are located on the easternmost and largest island, Hawaii (often referred to as the “Big Island”), where spectacular eruptions and lava flows take place from time to time. The Lō‘ihi Seamount, a growing volcano that could break the surface of the ocean tens of thousands of years from the present, is located 18.6 miles (30 km) southeast of the island of Hawaii. The highest Hawaiian mountains are Mauna Kea and Mauna Loa, both on the island of Hawaii, reaching 13,796 feet (4,205 meters) and 13,678 feet (4,169 meters) above sea level, respectively.

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There has been little erosion in the geologically young areas, where the terrain is domelike or scattered with hardened lava, and the volcanic craters are clearly defined. In the older areas the mountains have been shaped and eroded by sea, rain, and wind. Their aspects thus include sharp and craggy silhouettes; abrupt, vertically grooved cliffs pocked with caves; deep valleys; collapsed craters (calderas); and coastal plains. The powerful Pacific surf, churning and crashing against the fringing coral shelves and the lava shorelines, has carried minute shells onto the shore and reduced coral and large shells to sand, creating the state’s famous expanses of beach.

Heavy rainfall in mountainous areas produces an extremely voluminous runoff, which is responsible for the erosion that forms the numerous grooves, ridges, and V-shaped valleys characteristic of the older volcanic islands such as Kauai and Oahu. The action of rain combined with waves has had a particularly dramatic effect on the more exposed windward sections of the islands.

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