Properties of Igneous Rocks - The following properties are found in the igneous rocks:-
(1) Magmatic consolidation - The igneous rocks do not exhibit ordinary layers. The layers of igneous rocks are formed on account of the deposition of erupted lava at different intervals of time. These layers, in facts, represent the time intervals between successive magnetic eruptions.
(2) Both Crystalline and Non-Crystalline-The igneous rocks are crystalline as well as non-crystalline. If the magma arising out of fissures is cooled at a fast rate, it does not get sufficient time to crystallize and is therefore non-crystalline. When the magma does not come out but cools in the various empty spaces below the surface of the Earth, it cools slowly and crystalizes. The lower is the rate of cooling, the bigger would be the crystals. Hence, the crystals do not have a definite order or shape but their formation depends upon local conditions.
(3) Non-porous - These rocks are non-porous for water. The water cannot percolate through them.
(4) Poorly eroded - These rocks are hot subject to strong erosion. They resist erosion but their weathering goes up at a slow rate.
(5) Content of Silica - These rocks contains silica from 40 to 80%. Among others, Magnesium and Iron are important.
(6) No Fossils - These rocks do not have fossils.
Sub-classification of Igneous Rocks - The igneous rock can be further classified on many bases. For example, the rate of cooling of magma depends upon the minerals present in it. Besides minerals, the classification is also made on the basis of their shape and situation in which these rocks were formed.
"The world is a book, and those who do not travel read only a page", St. Augustine said. Here at www.travel-university.org we believe that every page must be read and explored. Travel is an avenue of learning that no text or classroom can teach. The world is a living classroom and you the student. We invite you to the www.travel-university.org library where you can read general interest and detail oriented articles.
