Bombs and Walls Might Slow Lava, But Not Stop It

[jakeXT]

For the Hawaiian town of Pahoa, there is no easy way to stop the smoldering lava pouring from the Kilauea volcano.

In other places and at other times, people have blasted molten rock with seawater, built barriers, and even dropped bombs on lava to keep it from destroying property. But when the 2,000-degree river hits Pahoa, residents will be able to do little more than watch.

Kilauea on Hawaii's Big Island has been continuously erupting since 1983, with most of the lava flowing into the ocean. A new vent began spewing molten rock in June. The lava is now at the doorstep of Pahoa, threatening the homes of its nearly 1,000 residents.

The big problem is that while lava flows can be diverted they can't be stopped entirely, and it's very hard to predict where they will go.

http://www.nbcnews.com/science/environment/bombs-walls-might-slow-lava-not-stop-it-n236591

[SheilaT]

1. Unfortunately, in movies they do silly things like that and

of course it works, so average people, who think that everything out of Hollywood must be true, don't understand how things like lava really work.

This past weekend I was at Mile Hi Con in Denver, a science fiction convention, and one of the panels was about stupid geology in movies and on TV. This is exactly the sort of thing that got cited. That and some movie in which to do something or another, the plan was to drop bombs down an active volcano so as to trigger a magnitude 17 earthquake. Clearly the people doing that hadn't a clue what the logarithmic scale of earthquake magnitudes really meant. I forget the details, but essentially if such an earthquake could be triggered, it would cause so much heat that the earth would be vaporized. Or if not vaporized, the shaking would last a really long time, something like thousands of years.

Anyway, getting science from real scientists rather than popular media is a good idea.

[jakeXT]

2. Up to magnitude 10 is what I've always heard, and a successful lava stopping operation was Heimaey

Can “Mega Quakes” really happen?
THEORETICALLY, YES. REALISTICALLY, NO. The magnitude of an earthquake is related to the length of the fault on which it occurs -- the longer the fault, the larger the earthquake. The San Andreas Fault is only 800 miles long. To generate an earthquake of 10.5 magnitude would require the rupture of a fault that is many times the length of the San Andreas Fault. No fault long enough to generate a magnitude 10.5 earthquake is known to exist. The largest earthquake ever recorded was a magnitude 9.5 on May 22, 1960 in Chile on a fault that is almost 1,000 miles long. The magnitude scale is open-ended, meaning that science has not put a limit on how strong an earthquake could be, and scientists can’t rule out a “Mega Quake” because they’ve only been measuring earthquakes for 100 years, a blink of an eye in geologic time. However, scientists agree that “Mega Quakes” of magnitude 10 or more are implausible.
http://earthquake.usgs.gov/learn/topics/megaqk_facts_fantasy.php

[SheilaT]

3. Thanks for some clarification.

The seismologist on the panel (he'd recently retired from a career at the earthquake center in Golden, CO) also said something about needing a fault that would circle the entire globe some improbably number of times.

I didn't take notes, and now wish I had.