Intrusive rock formed from magma that cools and solidifies within the crust of the planet. In contrast, an "extrusion" consists of extrusive rock; rock formed above the surface of the crust. Large bodies of magma that solidify underground before they reach the surface of the crust are called plutons. Plutonic rocks form 7% of the Earth's current land surface. Coarse-grained intrusive igneous rocks that form at depth within the earth are called "abyssal" while those that form near the surface are called subvolcanic or "hypabyssal". Intrusive structures are often classified according to whether or not they are parallel to the bedding planes
Lava is commonly shortened to "lava". Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic and shear thinning properties. Explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word "lava" comes from Italian, and is probably derived from the Latin word "labes" which means a fall or slide. The first use in connection with extruded magma (molten rock below the Earth's surface) was apparently in a short account written by Francesco Serao on the eruption of