Lava flow

Definition

A lava flow is a stream of molten rock that erupts from a volcano and moves down its slopes or spreads across the ground. These flows can vary in speed, composition, and temperature, influencing the formation of different volcanic landforms and types of igneous rocks as they cool and solidify.

5 Must Know Facts For Your Next Test

1. Lava flows can be classified into two main types: pahoehoe, which is smooth and ropy, and aa, which is rough and jagged.
2. The temperature of lava flows can range from about 700 to 1,200 degrees Celsius (1,292 to 2,192 degrees Fahrenheit), affecting their viscosity and flow characteristics.
3. Lava flows can travel at different speeds; some may move rapidly at several meters per second, while others may advance only a few centimeters per day.
4. The composition of the lava affects its flow behavior; for instance, basaltic lava is typically less viscous and flows more easily than andesitic or rhyolitic lava.
5. As lava cools, it solidifies into igneous rock formations, contributing to the development of volcanic landforms like shield volcanoes and stratovolcanoes.

Review Questions

• How do the physical properties of lava flow influence volcanic landform development?
  • The physical properties of lava flow, such as temperature, viscosity, and composition, significantly influence the type of landform that develops around a volcano. For instance, low-viscosity basaltic lava can travel further from the eruption site, creating broad shield volcanoes with gentle slopes. In contrast, more viscous lava forms steep-sided stratovolcanoes because it cannot flow as easily. This relationship between lava flow characteristics and landform shape highlights how volcanic processes shape the Earth's surface.
• Discuss the differences between pahoehoe and aa lava flows and their implications for volcanic hazards.
  • Pahoehoe lava flows are smooth and ropy, flowing easily over surfaces at higher temperatures. In contrast, aa flows are rough and jagged due to their higher viscosity and cooler temperatures. The implications for volcanic hazards differ as well: pahoehoe can create extensive areas with less immediate risk to structures due to its slower movement but may cover large regions over time. Aa flows can move more quickly and create sharp fragments that pose greater threats to nearby areas. Understanding these differences helps in assessing volcanic hazards and planning evacuations.
• Evaluate how changes in magma composition affect the behavior of lava flows during an eruption.
  • Changes in magma composition significantly affect the behavior of lava flows during an eruption by altering viscosity and gas content. For example, basaltic magma is low in silica and produces fluid lava flows that travel long distances. In contrast, more silica-rich magmas like rhyolite are highly viscous, leading to explosive eruptions that result in pyroclastic flows rather than extended lava flows. This variation impacts not only the immediate hazards associated with an eruption but also the long-term landscape evolution resulting from different types of volcanic activity.

Related terms

Magma: Magma is molten rock beneath the Earth's surface that, when it erupts, becomes lava.

Pahoehoe: Pahoehoe is a type of lava flow characterized by a smooth, ropy surface, often associated with basaltic lava that has a low viscosity.

Aa: Aa is a type of lava flow that has a rough, jagged surface and is typically more viscous than pahoehoe, leading to the formation of sharp fragments.