Yellowstone has long been a favourite among conspiracy theorists and scare mongeres alike. The national park is atop a magma chamber now estimated to be at least 18 miles wide and between 3 and 9 miles deep*. This creates some of the most famous and stunning hydrothermal activity in the world such as Old Faithful geyser that erupts on average 18-21 times a day**. It makes it almost impossible to deny that this supervolcano is still very active despite being around 640,00 years since its last eruption. Each past super eruption has spewed out in excess of 1000 cubic kilometres of material. The largest eruption in recorded history was Tambora’s 1815 catastrophe which only erupted about 50 cubic kilometres, yet was enough to change world climate for several years and kill over 100 000 people.
Lately Yellowstone has hit the headlines for a less extreme reason. Roughly 3 miles Firehole Lake Drive, a road leading to Old Faithful, had to be closed as the aspsalt had melted. Of course this lead to headlines of impending doom and an eruption around the corner as magma must be rising and melting the roads. Truth is this is normal behavior in a system as large as Yellowstone, there road closures are almost routine. Asphalt will start to soften at the low temperature of just 50 degrees Celsius and will be liquid at about 250. The rhyolitic lavas which typically erupt from the volcano have lows of 500 degrees Celsius which, if rising magma was a cause, would mean the road would be a near constant river state. The melting is actually cause by the same system that feeds Old Faithful, water. Water has an exceptionally high heat capacity which means ground water any where near the volcanic system can run at extremely high temperatures and either explode out to the surface as steam like at the geysers or heat the surface causing roads to melt.
This is a very common occurrence at Yellowstone and other volcanic sites around the world and is not a sign that Wyoming is about to blow. The Yellowstone Observatory*** constantly monitors activity in and around the park currently have alert levels set to normal. Seismicity is said to be at “normal back ground levels” and caldera uplift continuing as it has been at a slow rate since the beginning of the year now at about 3cm. If there were any signs of impending doom we should be able to know in advance.
* http://phys.org/news/2013-12-yellowstone-magma-bigger-thought.html accessed 17.7.14
*** http://volcanoes.usgs.gov/observatories/yvo/ accessed 17.7.14