Wednesday, May 16, 2018

Sakurajima Volcano with Lightning plus Moon Halo

from: NASA APOD

 
Image Credit & Copyright: Martin Rietze (Alien Landscapes on Planet Earth
 
Explanation: Why does a volcanic eruption sometimes create lightning? Pictured above, the Sakurajima volcano in southern Japan was caught erupting in 2013 January. Magma bubbles so hot they glowed shot away as liquid rock burst through the Earth's surface from below. The featured image is particularly notable, however, for the lightning bolts caught near the volcano's summit. Why lightning occurs even in common thunderstorms remains a topic of research, and the cause of volcanic lightning is even less clear. Surely, lightning bolts help quench areas of opposite but separated electric charges. Volcanic lightning episodes may be facilitated by charge-inducing collisions in volcanic dust. Lightning is usually occurring somewhere on Earth, typically over 40 times each second. 

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Moon Halo over Stone Circle

Image Credit & Copyright: Alyn Wallace Photography
Explanation: Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens. Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Moon Halo. A similar Sun Halo may be visible during the day. Exactly how ice-crystals form in clouds remains under investigation. In the featured image, the ice circle in the sky is mirrored by a stone circle on the ground. Taken just over a month ago in Pontypridd Common, Wales, UK, the central Rocking Stone survives from the last ice age, while the surrounding stones in the circles were placed much more recently -- during the 1800s.  

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