I have a serendipitous mix of topics for you today, including one that you might consider breaking news. I don’t pretend to be a news service, but sometimes it’s worth picking up on (sometimes sensationalist) headlines and looking at what’s actually happening.
Hawaii: The Big Island is Getting Bigger
It isn’t big news, unless you’re living in Hawaii, but the headlines in some news media will give you a clue that something’s happening in the middle of the Pacific. “Big Island Braces for Kilauea Eruption,” warns Hawaii News Today, while CBS News runs with: “Kilauea volcano in Hawaii could erupt after hundreds of small earthquakes”.
News media are a quick and easy source of information but they are rarely the best available. (It’s a particular bugbear of mine, and I’m sure of many other scientists in all fields, that the significant details are often and inevitably lost during the process of headline writing.) It’s always best, if you want to know what’s going on, to go direct to the most informed source. In this case, the best sources are the United States Geological Survey (USGS) and the Hawaiian Volcano Observatory (HVO).
The latest news from the HVO shows that a series of earthquakes has been occurring on the south-eastern flanks of Kilauea volcano, both on and offshore. In the past month almost 800 are shown on the interactive map, with magnitudes of up to M4.2.
The daily update for May 2 (the most recent available) gives more context. The monitoring of seismic and other activity leads to the view that: “An outbreak of lava from the lower East Rift Zone remains a possible outcome of the continued unrest,” which is probably not a surprise. After all, Hawaii is formed by volcanic activity and Kilauea itself has been erupting, albeit at a low level, since 1983.
Effusive volcanism of this nature (as opposed to more spectacular explosive volcanism) is what makes Hawaii grow, with layer upon layer of molten rock pouring up through rifts in the ground. Kilauea is on orange watch at the moment (“Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain OR an eruption is underway that poses limited hazards including no or minor volcanic-ash emissions”) and what’s going on is entirely normal.
Animals and Earthquakes: an Old Wives’ Tale?
It’s often claimed than animals can tell when a natural disaster is about to happen. (You’ll have seen the stories on the Internet, with herds of bison apparently fleeing Yellowstone ahead of the cataclysmic eruption that hasn’t yet happened.) This week there’s a new piece of research that looks at how solid (or not) the evidence is.
The USGS has a piece in its frequently asked questions section, in which it notes that the first suggestion of a connection dates back to as early as 373 BC and that “a once popular theory purported that there was a correlation between Lost Pet ads in the San Jose Mercury News and the dates of earthquakes in the San Francisco Bay area.” (There wasn’t, but it’s a good story.)
Studies have tended to pursue the theory that animals may be able to pick up sensitive earth movements or other environmental changes earlier than humans, but the timescale is very short — too short to do much to save an animal from a destructive earthquake.
This week, a study in the Bulletin of the Seismological Society of America published the results – not of a new theory, but of a thorough testing of the evidence for the old wives’ tale. They evaluated all reports they could identify, almost all of them anecdotal, and concluded that the evidence is not sufficiently robust to allow a definite conclusion.
“These weaknesses in the data,” says the Association’s news release, “make it difficult to confirm that these behaviors are predictive—meaning they signal an earthquake event before the event begins—rather than random occurrences or behaviors linked to the initial stages of an earthquake, such as foreshocks”.
North Korea: A Testing Time
I try to keep out of politics, for all sorts of reasons, but I don’t suppose there are many people who weren’t delighted by the new understanding between North and South Korea. While the former is known for its secrecy, there are some things you can’t hide, and the seismic signature of an atomic explosion is one of them — so it was easy enough to verify when and where nuclear testing had taken place.
The northern republic has conducted a series of nuclear tests, beginning in 2006 and concluding in 2017, with magnitudes increasing from M4.3 to M6.3. The most recent was followed by a separate aftershock with a magnitude of M4.1 (i.e. less than one-hundredth of the size of the main explosion). This later event is the subject of a new report published in Geophysical Research Letters.
Decoding seismic signals is phenomenally complicated, as a quick glance at the actual paper (which is freely available) will show — way too complicated for most of us to understand. But the conclusions of the paper are intriguing and they identify the origins of the second shock.
It was, they say, “neither a secondary explosion nor a triggered tectonic earthquake. It occurred due to a process comparable to a “mirror image” of the explosion, that is, a rock collapse, or compaction, for the ﬁrst time documented in North Korea’s test site.”