Lava flows: You can't stop them, you can only hope to contain them
Lava flows have returned to Kalapana - and although typically not dangerous to life, lava flows are very costly to property.
I write the Eruptions blog on Big Think. I've been mesmerized with volcanoes (and geology) all my life. It helps that part of my family comes from the shadow of Nevado del Ruiz in Colombia, where I could see first hand the deadly effects of volcanic eruptions. Since then, I've taken a bit of a winding path to become a volcanologist. I started as a history major at Williams College, almost went into radio, but ended up migrating to geology, including an undergraduate thesis on Vinalhaven Island, Maine. I followed this up by changing coast to get my Ph.D. from Oregon State University. Then I ran a MC-ICP-MS lab at University of Washington for a spell (and wrote for an indie rock website). I spent three years as a postdoctoral scholar at University of California - Davis studying the inner workings of magmatic systems. I am now an assistant professor at Denison University and have projects in New Zealand, Chile and Oregon.
I am fascinated by volcanoes, their eruptions and how those eruptions interact with the people who live around the volcanoes. I started this blog after getting frustrated with the news reports of volcanic eruptions. Most of them get the information wrong and/or are just sensationalistic. I will try to summarize eruptions as they occur, translate some of the volcanic processes that are happening and comment on the reports themselves.
And no matter what people tell you, I definitely do not have a cat named Tephra. (OK, I do).
You can find out more about my research by visiting my website. If you have any comments, questions or information, feel free to contact me at eruptionsblog at gmail dot com.
Lava flows from Kilauea in Hawai`i move towards a home in Kalapana.
Whenever I think about the hazards posed by most lava flows, I tend to think about the opening scene in the Hitchhiker's Guide to the Galaxy. Developers are planning to knock our hero Arthur Dent's house down and as a last ditch effort to stop its destruction, Arthur lies down in front of the bulldozer. The demolition supervisor, a certain Mr. Prosser, at one point asks Arthur if he knows how much damage the bulldozer might suffer if he just lets it roll over poor Mr. Dent. Arthur says he doesn't know and Mr. Prosser replies "none at all."
That is, in a nutshell, the hazard of lava flows. They can take out almost anything in their path, but really, you need to pull an Arthur Dent in most cases to put your life at risk*. Lava with low silica like a basalt will usually flow in one of two styles: runny pahoehoe and rubbly a'a. Whether you get pahoehoe or a'a is controlled by a number of factors including temperature of the lava, crystallinity, gas content, slope of the land surface (along with some other more minor factors), but even in its runny form (video), the pahoehoe, lava flows usually don't move too quickly - kilometers per hour at the fastest, more like meters to hundreds of meters per hour - and you can comfortably get out of the way. When they can become hazardous is when they are allowed to stay hot, either by traveling through a lava tube system underground (rock is a great thermal insulator) or by storing the lava in a lava lake and catastrophically releasing it (*such as what happened at Nyiragongo in 1977, killing over 1,000 people).
However, most of the time, lava flows are just destructive to property and plant life - slowly rumbling across the landscape like Mr. Prosser's bulldozer. A'a lava flows move like giant tank treads (video), with the main body of the flow overrunning the cooling nose, pushing that material underneath the lava flow. You can get lava flows of more silicic compositions, such as an andesite or rhyodacite, that have flow fronts that are tens to hundred meters tall, so if you can imagine a wall of hot rock 50 meters tall rumbling towards your home at a few meters a day, well, that is what some lava flows hazards are like. In Hawai`i, the pahoehoe and a'a lavas can easily inundate homes and infrastructure - as has been happening this week in the Kalapana subdivision on the slopes of Kilauea. There is little that can be done if a large lava flow heads into town - just hope that the flows misses your home so you can salvage what is left. If not, the lava flow will likely slowly engulf the home, crushing it and burning the remains.
So, not much can be done to stop a lava flow. There were attempts in the 1930-40s to bomb lava flows in Hawai`i to divert them or stop the flow, but that was, not surprisingly, unsuccessful. In very rare cases, lava flows have been diverted by setting up barriers, such as was done around Etna in Italy, or by pumping millions of liters of seawater on the lava flow to cool the flow front and change the direction of flow like was successfully done at Heimay in Iceland. However, beyond this, lava flows can be one of the most costly volcanic hazards in terms of property damage - not only will they destroy your home, but it will be buried and capped by hardened lava, so even soils take decades to recover. Yet, people still choose to build their homes on the slopes of Kilauea, knowing full well that the land they build on was once an active lava flow and more likely than not, these lava will return again to add to the Big Island.
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