Geologically, a volcanic island is an island of volcanic origin. The term high island can be used to distinguish such islands from low islands , which are formed from sedimentation or the uplifting of coral reefs (which have often formed on sunken volcanos).
7-743: The Intermontane Islands were a giant chain of active volcanic islands somewhere in the Pacific Ocean during the Triassic time beginning around 245 million years ago. They were 600 to 800 miles (1,300 km) long and rode atop a microplate known as the Intermontane Plate . Over early Jurassic time the Intermontane Islands and the Pacific Northwest drew closer together as the continent moved west and
14-516: A number of volcanic islands that rise no more than 1 metre (3 ft 3 in) above sea level , often classified as islets or rocks, while some low islands, such as Banaba , Henderson Island , Makatea , Nauru , and Niue , rise over 50 metres (160 ft) above sea level. The two types of islands are often found in proximity to each other, especially among the islands of the South Pacific Ocean , where low islands are found on
21-420: The fringing reefs that surround most volcanic islands. Volcanic islands normally rise above a hotspot or subduction zone . Volcanic islands usually range in size between 1 and 104 square kilometres (0.4 and 40 sq mi). Islands above a certain size usually have fresh groundwater , while low islands often do not, so volcanic islands are more likely to be habitable. Many volcanic islands emerge from
28-568: The Intermontane Islands and North America the Slide Mountain Ocean . This article about a specific Canadian geological feature is a stub . You can help Misplaced Pages by expanding it . This palaeogeography article is a stub . You can help Misplaced Pages by expanding it . This article related to an island or group of islands in Canada is a stub . You can help Misplaced Pages by expanding it . Volcanic island There are
35-627: The Intermontane Plate subducted . About 180 million years ago in the Mid-Jurassic time the last of the Intermontane Plate subducted and the Intermontane Islands collided with the Pacific Northwest , forming parts of British Columbia , Canada . The Intermontane Islands were too big to sink beneath the continent, and welded onto the continent, forming the Intermontane Belt . Geologists call the ocean that existed between
42-443: The deep abyss of the ocean, and feature rough or mountainous landscapes in their interiors and a diverse array of summit elevations. Researchers have observed that the island will often be covered by dense tropical forest. These limit settlement on the interior of many islands, forcing communities to develop along the coast. Larger islands may have rivers, resulting in flood hazards. Rivers deliver sediment downstream, which can dominate
49-473: The shape of the coast and contribute to erosion. Tall volcanic islands are often surrounded by protective fringing or barrier reefs, creating lagoons. The unique geological and geographical characteristics of volcanic islands make them prone to many natural hazards, which are expected to worsen due to climate change . These include volcanic eruptions, earthquakes, tsunamis, landslides, and severe weather events like hurricanes or typhoons. Studies have highlighted
#333666