Every year an internet hoax circulates that a Green Moon will appear on April 20 which happens to coincide with 4/20 – a number combination that is street slang for a time to smoke marijuana.
Although a hoax, Green Moons do occur sometimes – not because of what people smoke, but when the earth smokes.
Humans saw green and blue moons almost every night for a few years after the Krakatoa volcano exploded in 1883 with the force of a 100-megaton nuclear bomb. Plumes of ash rose to the very top of Earth’s atmosphere.
Some of those ash-clouds were filled with particles about 1 micron wide – just the right size to strongly scatter red light while allowing other colors to pass.
White moonbeams shining through those ash clouds emerged blue, and sometimes green.
People also saw blue and green-colored Moons in 1983 after the eruption of the El Chichon volcano in Mexico. And there are reports of blue Moons caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.
A Full Moon in April has had a colorful name for centuries before the Green Moon internet hoax.
April’s Full Moon is also called a Pink Moon because Colonial Americans learned that name from Native Americans who associated the April Full Moon with the blooming of pink flowers in early Spring named wild ground phlox, according to the Farmer’s Almanac.
Other names for April’s Full Moon are also associated with Springtime: Full Sprouting Grass Moon (sprouting vegetation in Spring), Egg Moon (animal mating in Spring), and Full Fish Moon (when fish spawn in spring).