Lava flows are streams of molten rock that emerge from a volcano during an eruption. When magma from beneath the Earth's surface reaches the surface, it becomes lava. The flow can vary in speed and temperature, depending on its composition and the slope of the land. As lava flows cool, they solidify into rock, creating new landforms. The type of lava, such as basalt or andesite, influences the flow's characteristics. These flows can be destructive, covering landscapes and altering ecosystems, but they also contribute to the formation of new geological features over time.