Volcanoes are generally not preserved in the geologic rock record as they are us
ID: 896080 • Letter: V
Question
Volcanoes are generally not preserved in the geologic rock record as they are usually eroded away. However, the various materials erupted from volcanoes are often found preserved in the rock record. From what you have learned about the different types of volcanoes, how could you infer what type of volcano erupted in a given area based on the type of volcanic deposits now found as layers of rock? Give specific examples, and briefly discuss how some materials may be linked to different types of volcanoes.
Explanation / Answer
There are actually three types of volcanoes namely shield, cinder and composite cones.
The shield cone looks like an inverted semi-sphere. This type of volcano does not burst out violently. Instead, it slowly expels rivers of lava for hundreds of meters, One good example of it is Mauna Loa, located in the volcanic islands of Hawaii. This volcano only slowly flows lava from its crater, and forms so called "ropes of cooled lava".
The cinder type looks like a medium-sized cone inverted. Violent eruptions may occur, but in rarity due to its small crater. And add that feature that it lacks "branches" to expel small rivers of lava. One example of that is Taal Volcano, a small volcano located in an island at Batangas, Philippines.
The composite cone is the famous of all, bearing the shape of a real cone (but not always perfect). In this type, more violent eruptions are more possible, due to its size and plenty of " branches" in its sides. To name a few, we have Pinatubo, St. Helens, Vesuvius, Fuji, Krakatoa, and scores of others.
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