Extrusive rocks are a type of igneous rock that forms when molten rock, or magma, erupts onto the Earth's surface as lava. Once exposed to the cooler temperatures of the atmosphere or ocean, the lava rapidly cools and solidifies. This process results in fine-grained textures, as the minerals do not have much time to grow. Common examples of extrusive rocks include basalt and pumice. These rocks are often found in volcanic regions and can create various landforms, such as lava flows and volcanic islands. Their formation is a key part of the rock cycle, contributing to the Earth's geological diversity.