The mysterious moving stones of the packed-mud
When a thick lava flow cools it contracts vertically but cracks perpendicular to its directional flow with remarkable geometric regularity - in most cases forming a regular grid of remarkable hexagonal extrusions that almost appear to be made by man. One of the most famous such examples is the Giant's Causeway on the coast of Ireland (shown above) though the largest and most widely recognized would be Devil's Tower in Wyoming . Basalt also forms different but equally fascinating ways when eruptions are exposed to air or water.
Blue holes are giant and sudden drops in underwater elevation that get their name from the dark and foreboding blue tone they exhibit when viewed from above in relationship to surrounding waters. They can be hundreds of feet deep and while divers are able to explore some of them they are largely devoid of oxygen that would support sea life due to poor water circulation - leaving them eerily empty. Some blue holes, however, contain ancient fossil remains that have been discovered, preserved in their depths.
Red tides are also known as algal blooms - sudden influxes of massive amounts of colored single-cell algae that can convert entire areas of an ocean or beach into a blood red color. While some of these can be relatively harmless, others can be harbingers of deadly toxins that cause the deaths of fish, birds and marine mammals. In some cases, even humans have been harmed by red tides though no human exposure are known to have been fatal. While they can be fatal, the constituent phytoplankton in ride tides are not harmful in small numbers.
True to their ominous appearance, mammatus clouds are often harbingers of a coming storm or other extreme weather system. Typically composed primarily of ice, they can extend for hundreds of miles in each direction and individual formations can remain visibly static for ten to fifteen minutes at a time. While they may appear foreboding they are merely the messengers - appearing around, before or even after severe weather.
A circumhorizontal fire rainbow arc occurs at a rare confluence of right time and right place for the sun and certain clouds. Crystals within the clouds refract light into the various visible waves of the spectrum but only if they are arrayed correctly relative to the ground below. Due to the rarity with which all of these events happen in conjunction with one another, there are relatively few remarkable photos of this phenomena.