There are over 700 hundred types of igneous rocks, and they are generally the hardest and heavies t o f all rocks. Not all magma is made equa lly: different magmas can have different chemical compositions, different quantities of gases and different temperature - and different types of magma make different types of rocks. Basalt - note the almost complete lack of visible crystals. Some volcanic rocks (like obsidian) don’t have any crystals at all. Volcanic rocks are also called extrusive igneous rocks, as opposed to intrusive igneous rocks. The classical example here is basal t, which can have many small crystals or very few large ones. However, if the magma erupts or is cooled rapidly, you instead get a volcanic rock – – not really igneous, but also originating from lava. Image modified from Eastern Illinois University. Note the white, almost rectangular feldspar crystals, the grey virtually shapeless quartz crystals, and the black crystals, which can be either black mica or amphibole. The crystals are also differentiated, as you can see below. That’s why you see rocks such as granite with big crystals - the magma had time to cool off. As you go deeper underground, the temperature rises go further and you’ll eventually reach the Earth’s mantle - a huge layer of solid rock surrounding the Earth’s core (which, in geologic time, behaves as a viscous liquid).Īs you probably know, when magma cools, it turns into rock if it cools while still underground at high temperatures (but at temperatures still lower than that of the magma), the cooling process will be slow, giving crystals time to develop. Magma is composed of a mixture of molten or semi-molten rock, along with gases a nd other volatile elements. Lava is the extrusive equivalent of magma.

Now, the long story, which is much more interesting, is this: Igneous Rocks Lava flow on Hawaii. N ow the long story, which is much more interesting, is this: They can be formed from organic remains (such as limestone), or from the cementing of other rocks. Sedimentary - they are formed through the solidification of sediment.They can form both underground and at the surface. Metamorphic - they are formed through the change (metamorphosis) of igneous and sedimentary rocks.They often have large crystals (you can see them with the naked eye). Igneous - they form from the cooling of magma deep inside the earth.It’s the first thing you learn in a geology class - very briefly the three types of rocks are:

Different types of fit bits