As the Pacific Plate moves north-west over the plume huge amounts of basalt have accumulated on the ocean floor to produce the Hawaiian islands. This is a fixed area of volcanic activity where magma rises from a mantle plume. Hawaii was formed due to a volcanic hot spot. The chain of islands that form Hawaii lie at the centre of the Pacific Ocean, thousands of miles away from a plate margin. Iceland owes its existence to effusive eruptions at a divergent margin between the North American and Eurasian plates. Examples of shield volcanoes include Mount Kilauea and Maunaloa on Hawaii. Shield volcanoes are usually found at divergent (constructive) boundaries and sometimes at volcanic hotspots. Although these eruptions destroy property, death or injury to humans rarely occurs.Ī simple cross-section of a shield volcano Eruptions tend to be frequent but relatively gentle. Shield volcanoes produce fast flowing basic (fluid) lava that can flow for many miles. Shield volcanoes are low with gently sloping sides and are formed from layers of lava. Over time denudation creates a more varied relief. When they are formed they have a slope of 1°. One example is the Deccan Plateau in central India. When basic lava flows from many fissures large areas can be covered by free-flowing lava known as flood basalts. The products of effusive eruptionsĪn effusive eruption is a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground. ![]() Without magma providing support below a caldera is formed when the sides of the volcano collapse. They form when an explosive eruption destroys the cone and the magma chamber below is emptied. CalderasĪ caldera is a volcanic crater, usually more than 2km in diameter. There are 66 strato-volcanoes in the Andes that have recently erupted. Convergent plate boundaries and explosive eruptions give rise to chains of strato-volcanoes. Examples of composite volcanoes include Mount Fuji (Japan), Mount St Helens (USA) and Mount Pinatubo (Philippines). ![]() ![]() Composite volcanoes are usually found at destructive plate margins. The thick lava cannot travel far down the slope of the volcano before it cools. This viscous lava has a lot to do with why they are shaped the way they are. Eruptions are explosive due to the thick, highly viscous lava that is produced by composite cone volcanoes. When composite volcanoes erupt they are explosive and pose a threat to nearby life and property. A simple cross-section of a composite volcano
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