Washington, wildfires and kilauea geoscience 19-25 july 2018

I want to start with the story of Washington State, but in truth I’m finding it a little frustrating. This week I saw a story in the news that, while quoting requirable geoscientists, doesn’t seem to have a link to a specific piece of research (certainly not as far as I can tell from the articles to which I have access) and yet that looks as if it’s interesting enough to be part of a bigger story.

Let’s start with small earthquakes. The Seattle Times is running with the headline “ Tremors shove Washington westward, offer clues into next big earthquake”. Unfortunately I can’t publish the graphic from the Seattle Times for copyright reasons, but I can tell you that it shows a very large number of earthquakes — probably hundreds — from a point roughly south of Olympia to approximately the middle of Vancouver Island.

The graphic I’ve included is for comparison purposes and is taken from the United States Geological Survey’s interactive earthquake archive and shows earthquakes of at least M2.5 in the region since mid-May this year. You’ll notice there are very few. The tremors occurring in Washington and on Vancouver Island are too small to be included.

In itself this tells us something, but it’s only part of a complicated story. Tectonically, this marks the line of a major — but quiet — subduction zone called Cascadia, along which the Pacific plate descends beneath the North American continent. Cascadia is noted for a very large earthquake which took place way back in 1700, but has been quiet since.

That’s quiet in terms of large earthquakes, or even small ones. What’s been happening is a burst of tiny tremors, and it isn’t unusual. It’s a phenomenon known as episodic tremor and slip and it’s defined (in this case by the Pacific North West Seismic Network as: “ a process that occurs deep below the Earth’s surface, along faults that form the boundaries of tectonic plates. It involves repeated episodes of slow sliding, one plate over the other, of a few centimeters over a period of several weeks, accompanied by energetic seismic noise, called tremor.”

The natural world brings us some grim news footage. An unprecedented hot, dry spell across much of the world has led to what appears to be an increasing trend of major, destructive and fatal fires, not just in rural areas but affecting urban settlements too. This morning, the news outlets are reporting over 70 people killed in a series of fires in Greece. Last year there were major fires in (among others) California, Portugal and Australia.

The link between global warming and fires such as these is currently much-discussed, though as yet unproven. 2017 has been described as “ the most destructive in U.S. history”. In May, before the current outbreak of summer fires, the European Geosciences Union blog took a look at the links between climate change and wildfires and it makes sobering reading.

What this analysis suggests is that climate change is contributing to the factors which make these fires so devastating — for example, long periods of hot and dry weather, but also changes in weather patterns. Perhaps most crucial, the blog highlights a feedback effect — fallout from an increasing number of high-latitude fires could affect the reflectivity of the ice caps and increase warming further.

The IPCC’s report on climate change in 2014 warned that: “ Impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones and wildfires, reveal significant vulnerability and exposure of some ecosystems and many human systems to current climate variability”. It looks as though we’re seeing a part of that on the news right now. Kilauea Keeps Going