Distant thunderheads?

Or atmospheric refraction? Click on the picture to take a closer look. In fact it's the latter, refraction. The photo was taken from Mauna Kea's summit a few minutes after the sun had set and shows some distant clouds still back-illuminated by the sun. Layers of air with different temperatures cause the light to refract differently which can give rise to all sorts of curious effects and shapes, especially around sunset as the earth's surface starts to cool off.

The refraction effect that caused these odd cloud shapes is the same one Pam and I saw from Moonstone Beach in Cambria, California, shown in the picture below.