This photograph shows a fountain of liquid magma during the eruption of Stromboli volcano in Italy.
Click on image for full size
Image from Dr. J. Alean, Eglisau, Switzerland
For more information, images and video about Stromboli volcano see Stromboli On-Line.
Extrusive Igneous Rocks
Extrusive igneous rocks, or volcanics, form when magma makes its way to Earth's surface. The molten rock erupts or flows above the surface as lava, and then cools forming rock. The lava comes from the upper mantle layer, between 50 km and 150 km below the Earth's surface.
When lava erupts onto the Earth's surface, it cools quickly. If the lava cools in less than a day or two, there is no time for elements to form minerals. Instead, elements are frozen in place within volcanic glass. Often, lava cools over a few days to weeks and minerals have enough time to form but not time to grow into large crystals.
Basalt is the most common type of extrusive igneous rock and the most common rock type at the Earth's surface.
Last modified June 17, 2003 by Lisa Gardiner.
Shop Windows to the Universe Science Store!
The Fall 2010 issue of The Earth Scientist
, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!
You might also be interested in:
If you could travel to the center of the Earth, you would find that it gets hotter and hotter as you travel deeper. The heat is naturally produced when radioactive elements break apart. Within the Earth’s...more
Everything you see around you is made of tiny particles called atoms. There are many different types of atoms, each with a special combination of protons , neutrons and electrons . These different types...more
Minerals are the building blocks of rocks. They are non-living, solid, and, like all matter, are made of atoms of elements. There are many different types of minerals and each type is made of particular...more
An element (also called a "chemical element") is a substance made up entirely of atoms having the same atomic number; that is, all of the atoms have the same number of protons. Hydrogen, helium, oxygen,...more
Basalt is an extrusive igneous rock that is very dark in color. It is the most common type of rock in the Earth's crust and it makes up most of the ocean floor. It is made of many dark colored minerals...more
Spotting minerals is fun! There are many different types of minerals, each with a different name and a special set of characteristics. So, if you find a mineral that you do not recognize, you can use...more
Quartz is one of the most common mineral in Earth’s crust! Silica (Si) and Oxygen (O) are the only elements within pure quartz. If a cooling magma has silica leftover after feldspars form, quartz is likely...more