Scoria
From Free net encyclopedia
Image:ScoriaUSGOV.jpg Scoria is a type of igneous rock containing many gas bubbles, or vesicules. This rock is most commonly associated with Basalt, a mafic igneous rock. It forms when magma rich in dissolved gases is vented. As the magma encounters lower pressures, the gases are able to escape and form bubbles. These bubbles are trapped when the magma cools and solidifies. Volcanic cones of scoria can be left behind after eruptions, usually forming mountains with a crater at the summit. An example is Mount Wellington, Auckland in New Zealand. Another material can be formed during burning eruption of a mud volcano, when heated mud forms scoria cones. Natural coal fires have also created large deposits of material which have erroneously been called scoria. Scoria contains large amounts of iron and magneseium (this will lead to a dark colour), and is dense.
