April 22, 2024
A birthday is what happens when cosmic time briefly puts down the scale of eons and pays attention to a single human year.
Moon and Smoke Rings from Mt. Etna
Birthday · April 22, 2024
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APOD published April 22, 2024. Credit: Dario Giannobile. A publication-date match, not a photo taken on your date. Independent of NASA.
Yes, but can your volcano do this? To the surprise of some, Mt. Etna emits, on occasion, smoke rings. Technically known as vortex rings, the walls of the volcano slightly slow the outside of emitted smoke puffs, causing the inside gas to move faster. A circle of low pressure develops so that the emitted puff of volcanic gas and ash loops around in a ring, a familiar geometric structure that can be surprisingly stable as it rises. Smoke rings are quite rare and need a coincidence of the right geometry of the vent, the right speed of ejected smoke, and the relative calmness of the outside atmosphere. In the featured image taken about two weeks ago from Gangi, Sicily, Italy, multiple volcanic smoke rings are visible. The scene is shaded by the red light of a dawn Sun, while a crescent Moon is visible in the background.
Image credit: Dario Giannobile