How Do Extrusive Igneous Rocks Form - Web the most common extrusive igneous rock is basalt, a rock that is especially common below the oceans (figure 4.6). Web extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Web extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the earth's surface. Web extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the earth flows out (extrudes). Some cool so quickly that.
Web extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Web the most common extrusive igneous rock is basalt, a rock that is especially common below the oceans (figure 4.6). Web extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the earth's surface. Some cool so quickly that. Web extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the earth flows out (extrudes).