The Mount St. Helens blast was heard 172 miles away

Evidence

The farthest I have heard a sound travel was 172 miles, roughly the width of Washington State. This occurred on May 18, 1980, when I was fly-fishing in North Cascades National Park near the Canadian border. Dynamite, I thought. But Sunday morning? Minutes later, other blasts arrived from different directions. Hours later, ash fell from the sky. Mt. St. Helens had blown! … The subsequent blasts were not, in fact, true echoes, but rather different sound paths traveling different paths at different speeds due to variations in temperature and atmospheric pressure. — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 955

Categorization

• XREF: A dramatic concrete instance of the book’s claim that nature can shout — and of sound traveling far in quiet country.
• corroborated: 2 independent passages support this claim — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 955