8 September 2017 — 0724 mdt
Did a Montana newspaper commit the
largest numerical error in journalism history?
Over the course of the day, prevailing winds blew 520 million tons of ash eastward across the United States and caused complete darkness in Spokane, Washington, 400 km (250 mi) from the volcano. Major ash falls occurred as far away as central Montana, and ash fell visibly as far eastward as the Great Plains of the Central United States, more than 1,500 km (930 mi) away. The ash cloud spread across the U.S. in three days and circled the Earth in 15 days.
In all likelihood, yes — and the honor belongs to the now defunct Kalispell Weekly News. Here’s what happened.
Fine volcanic ash reached the Flathead less than a day after Mount St. Helens erupted on 18 May 1980. Very fine, but gritty, it filled the Flathead Valley with a powdery tan cloud, limiting visibility, and giving the air a heavy feeling when breathed (that didn’t stop some fools from jogging).
Rough measurements produced startling, four-figure, values for suspended particulates, which are reported as micrograms per cubic meter (µg/m^3). In Kalispell, the peak particulate concentration was 7,355 µg/m^3.
But the KWN’s reporter, a competent journalist working under great stress and unfamiliar with air quality issues, reported the value as 7,355 megagrams per cubic inch (I’m working from memory, as I think I discarded the clipping). That translates to 449 million kilograms per cubic meter, 80,000 times the density of the planet Earth, and half the density of a white dwarf star (but just one-millionth the density of a neutron star).
I reckon the error as 12 orders of magnitude, but urge readers to make their own calculations and to let me know if I missed the mark, and so, by how much.