![]() ![]() Another way to stop a lava flow is to increase the lava flow's viscosity (Bryant, 1991 and Scott, 1989) by spraying it with water, increasing the rate at which gas escapes from the flow, stirring the flow, or seeding the flow with foreign nuclei (Bryant, 1991). ![]() But how do you stop a lava flow if you know it's heading toward your property? Different methods have been used including: breaching the sides of a lava tube or channel, diverting the flow, constructing barriers, and bombing the lava flow. They can travel at 80km/h, significantly faster than lava flows. Equations have been used to estimate this distance (see Pinkerton and Wilson, 1994). Pyroclastic flows are eruptions of rock, ash, and gas that are superheated. The main concern with lava flows is how far they will ultimately extend. Melting of ice beneath a glacier may produce very large floods called jokulhlaups or glacier bursts (Bryant, 1991) Lava flows can also dam rivers which may in the future produce flooding if the dam were to break, though most lava flows are fairly porous (Scott, 1989). Electric power, water, and communications were cut off from the community.Īnother hazard associated with lava flows (as well as other hot volcanic material) is they can melt snow and ice which can produce flooding. Lava flows buried cars and burnt homes, buildings, and vegetation. In the late 1980's, the town of Kalapana in Hawai'i was destroyed by lava flows. The biggest hazard of lava flows is that they destroy property. It can take days to years for a lava flow to completely cool. Their eyebrows, and melted the soles of their boots from being near or on a hot lava flow. However, lava flows are very hot (between 550 degrees C and 1400 degrees C) and can therefore cause injuries. Lava flows as you can see don't move very fast so people rarely get killed by them. If a lava flow is channelized or travels underground in a lava tube then the distance it travels is greatly extended. These flows can move at rates of a few to hundreds of meters per hour (Scott, 1989). More silica-rich flows can move as far away as 1.3 km from their sources and have thicknesses of 100 m (Bryant, 1991). These flows can move at rates of several kilometers per hour (Scott, 1989). Such a flow can move as far away as 4 km from its source and have a thickness of 10 m (Bryant, 1991). A basalt flow like those in Hawai'i have low silica contents and low viscosities so they can flow long distances. Such a flow would have a high viscosity (a high resistance to flow). ![]() A cold lava flow will not travel far and neither will one that has a high silica content. How far a lava flow travels depends on the flows temperature, silica content, extrusion rate, and slope of the land. Caption by Erik Klemetti (Denison University) and Adam Voiland (Earth Observatory).Lava flows are the least hazardous of all processes in volcanic eruptions. NASA Earth Observatory images by Robert Simmon, using Landsat 8 data from the USGS Earth Explorer. Like Chao, the flows shown above have pressure ridges caused by the compression of the cooling top of the lava as the flow advanced. They have smaller flow fronts (10 to 30 meters tall) in comparison to the sheer 400-meter cliffs at Chao, as well as more prominent lava levees along the edges. In comparison to the Chao dacite in Chile (the product of viscous lava), the flows at Zhupanovsky and Dzenzursky are much narrower and longer. These features form as lava cools and hardens along the edges or top of a flow while the center of a flow still advances. Distinctive lava levees are visible along the edges of many of the younger flows. The exact ages of the flows are unclear, but the eruptions that produced them likely occurred during the past few thousand years. In the image, younger lava flows appear grey, while older flows are covered by green vegetation. The image was acquired by the Operational Land Imager (OLI) on the Landsat 8 satellite on September 9, 2013. Many characteristics of a low-viscosity lava flow are visible in this image of Zhupanovsky and Dzenzursky volcanoes on Russia’s Kamchatka Peninsula. They also tend to have smaller flow fronts and levee-like structure along their edges. While viscous lava flows are defined by steep flow fronts and pressure ridges, low-viscosity lavas tend to move faster and create longer, narrower shapes. These rivers of rock can take many shapes and move at very different rates depending on the viscosity of the magma, the slope of the land, and the rate of an eruption. Streams of molten rock that ooze from gaps or vents in the Earth’s surface are called lava flows, and they can pose a hazard to everything in their paths. Read part 1 of this story to see an example of a lava dome created by highly viscous lava.
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