What are volcanoes?
Welcome to Quatr.us Study Guides!

What are Volcanoes?

Mount St. Helens
Mount St. Helens volcano erupting

Volcanoes are places where the plates of the Earth's surface have cracks in them, so that the very hot melted rocks that are under the tectonic plates bubble up to the surface. The hot melted rocks are called magma. The magma is under a lot of pressure inside the Earth's plates, so when it gets a chance to let off some of that pressure by shooting out into the air, it does just that. There are volcanoes on other planets, too.

Probably in the early years just after the planet Earth formed, about four and a half billion years ago, there were a lot more volcanoes than there are now, and they erupted more frequently. It may be that the heat from these volcanoes was what warmed up the water in the oceans so that it melted and got warm enough to make proteins into proteinoids, part of the beginning of life on Earth. Volcanoes also may be the thing that created land, by shooting up rocks into the ocean that covered the whole Earth, and then piling those rocks up, eruption after eruption, until the tops of the piles stuck out of the water and became islands.

While volcanoes are very dangerous to people when they are erupting, after the eruption volcanoes still bring many useful things to plants and animals. The magma that shoots out of the volcanoes cools into different kinds of igneous and metamorphic rocks like lava, quartz, pumice, granite, and basalt, and when these rocks wear down and become dirt it is very rich dirt that is good for growing plants. The obsidian, or volcanic glass, made good sharp tools for Neolithic farmers, and even today doctors still use obsidian for knives for operations.

Learn by doing - different kinds of rocks
More about earthquakes

Bibliography and further reading about volcanoes:

More about igneous rocks
Quatr.us home


LIMITED TIME OFFER FOR TEACHERS: Using this article with your class? Show us your class page where you're using this article, and we'll send you a free subscription so all your students can use Quatr.us Study Guides with no distractions!
Please help other teachers and students find us: link to this page from your class page.
Karen Carr is Associate Professor Emerita, Department of History, Portland State University. She holds a doctorate in Classical Art and Archaeology from the University of Michigan. Follow her on Instagram or Twitter, or buy her book, Vandals to Visigoths.
Cite this page
  • Author: K.E. Carr
  • Title:
  • Site Name: Quatr.us Study Guides
  • Publisher: Quatr.us
  • Date Published:
Proud of your class page, homework page, or resource page? Send it in and win a Quatr.us "Great Page!" award!
Sign up for more free articles and special offers in Quatr.us' weekly newsletter:
We will never share your e-mail address unless you allow us to do so. View our privacy policy. Easy unsubscribe links are provided in every email.
Comment on This Article

Does your class page honor diversity, celebrate feminism, and support people of color, LBGTQ people, and people with disabilities? Let us know, and we'll send you a Diversity Banner you can proudly display!
Looking for more?
Quatr.us is loading comments...
(Comments will appear after moderation, if they are kind and helpful. Feel free to ask questions, and we'll try to answer them.)
Cite this page
  • Carr, K.E. . Quatr.us Study Guides, . Web. 22 March, 2017
ADVERTISEMENT