Lavaströme

Lavaströme (lava flows) are surfaces of molten rock that move downslope after an eruption. They originate when magma reaches the surface or breaches a lava chamber and continues to flow as long as heat remains and the crust has not yet solidified.

Flow behavior is controlled by magma viscosity, temperature, composition, gas content, and the topography over which it travels. Low-viscosity magmas, such as basalt, tend to flow rapidly and produce smooth, ropey surfaces known as pahoehoe. Higher-viscosity magmas, including andesite and rhyolite, move more slowly and often form rough, blocky surfaces called aa. Flows can advance as open-channel rivers or as sheet flows and may travel through lava tubes when the crust insulates the interior.

Surface textures: Pahoehoe crust forms a glassy, sheen-like layer with braided, rope-like ridges. Aa crust breaks into angular blocks as it advances. The crust can fortify the leading edge while trapped interior magma continues to advance, creating lobes and toes.

Emplacement and impact: Lava flows modify landscapes by burying vegetation and infrastructure, filling valleys, and altering drainage patterns. They rarely explode during emplacement, but eruptions beneath or within the flow can re-ignite surface movement. Topography, vent location, and eruption rate strongly influence flow paths and speed.

Monitoring and hazards: Communities in lava-flow zones use barriers, diversion channels, and early-warning systems. Scientists monitor temperature, flow rate, ground deformation, and gas emissions using satellites, infrared cameras, and field surveys to forecast paths and potential impacts. Global examples include long-lived flows from volcanoes such as Kīlauea and Etna, which have shaped surrounding terrain and infrastructure.