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largely go unnoticed by people. Yet the eruptions from submarine volcanoes hugely exceed all the eruptions on land.
Stratovolcanoes
Stratovolcanoes are the most numerous of the world’s volcanoes, making up 577 of the world’s 1300 active volcanoes. The upper parts of the cones of stratovolcanoes have steep sides with angles up to 35°. Most stratovolcanoes have a summit crater, and most contain andesite.
Shield volcanoes
shield volcanoes are the second most numerous,
with 107 of the world’s total. The word shield is used because of their resemblance to the shape of a Hawaiian fighting shield when resting on the ground. They are generally enormous volcanoes that have a dome shape (convex slopes, as opposed to the concave slopes of
a stratovolcano). Most shield volcanoes contain only basalt. Investigations show that the number of layers making up a shield volcano is even larger than that for
a stratovolcano, representing evidence of hundreds of thousands of eruptions. The largest of these volcanoes are very old, certainly over a million years. The summits of shield volcanoes are gentle, with slopes below 6°. They
Pillow lava on land. This rock was once part of the sea bed and the lava erupted under a great depth of water. The pillows characteristically have an open centre.
(Below) The stratovolcano of El Misti in the Peruvian Andes.
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