GEOLOGY

Detailed explanation-1: -Oceanic islands (4), also known as volcanic islands, are formed by eruptions of volcanoes on the ocean floor. No matter what their height, oceanic islands are also known as “high islands.” Continental and coral islands, which may be hundreds of meters taller than high islands, are called “low islands.”

Detailed explanation-2: -HOW ARE VOLCANIC ISLANDS FORMED? Volcanic islands are formed by volcanic activity on the seabed, often near the boundaries of the tectonic plates that form Earth’s crust. Where two plates pull apart, lava erupts to form an undersea ridge. Layers of lava build up until a ridge breaks the sea’s surface to form an island.

Detailed explanation-3: -Volcanoes are Earth’s geologic architects. They’ve created more than 80 percent of our planet’s surface, laying the foundation that has allowed life to thrive. Their explosive force crafts mountains as well as craters. Lava rivers spread into bleak landscapes.

Detailed explanation-4: -The word “archipelago” comes from the medieval Italian word archi, meaning chief or principal, and the Greek word pelagus, meaning gulf, pool, or pond. Most archipelagos are formed when volcanoes erupt from the ocean floor; these are called oceanic islands.

Detailed explanation-5: -Volcanic islands occur in ocean basins (such as the Hawaiian Islands) or on or near ocean ridges (e.g., St. Paul Rocks and Ascension Island in the Atlantic Ocean) (Fig. 1.3). They are large volcanoes erupted on the seafloor whose tops have emerged above sea level.