Page 39 - Curriculum Visions Dynamic Book. To close the book, close the window or tab.
P. 39
associated with extremely violent eruptions.
Obsidian is a volcanic glass extremely rich in silica. It
normally forms on the surfaces of very sticky lava.
Shapes of volcanoes
The most perfectly shaped volcanoes are usually
those with long histories of moderate explosions. Volcanoes with extremely violent histories are often less elegantly shaped because of the destruction that the eruption causes to the summit of the volcano.
Mount Fuji in Japan and Mount Mayon in the Philippines are often thought of as two of the most elegantly shaped volcanoes in the world. Their symmetrical concave-upwards profiles are the result of thousands of moderately sized eruptions.
In most eruptions the early stages are the
Andesite
(On this page) A selection of common volcanic rocks.
Basalt
39
