In geology, an extrusion refers to the process by which molten rock, or magma, is expelled from a volcano or fissure onto the Earth’s surface. This can result in the formation of various volcanic features, including lava flows, lava plates, and volcanic domes.
When magma reaches the surface, it is called lava. The temperature and pressure under which this process occurs cause the magma to become less viscous, allowing it to flow out easily. Extrusions can vary significantly in their physical properties based on the magma’s composition, rate of flow, and the amount of gas dissolved in it. For example, basaltic lava tends to flow more easily and can cover large areas, while more viscous lava, such as andesitic or rhyolitic, might build up forming steep volcanic structures.
The study of extrusions is essential in understanding volcanic activity, predicting future eruptions, and assessing potential hazards associated with volcanoes. By examining the patterns and characteristics of extruded materials, geologists can gain insights into the inner workings of the Earth’s magma systems.