Lava is molten rock that erupts from a volcano during a volcanic eruption. When magma, which is found beneath the Earth's surface, rises and breaks through the crust, it becomes lava. This hot, liquid rock can flow down the sides of a volcano and spread across the land, cooling and solidifying into igneous rock. Lava can vary in temperature, composition, and viscosity, affecting how it flows. There are different types of lava, such as pahoehoe, which is smooth and rope-like, and aa, which is rough and jagged. The type of lava influences the landscape and can create new landforms over time.