Originally Published in ‘Georgian Journal’. Issue No.17 (102)
Original Link: http://www.kvirispalitra.ge/gj-site/2009/17-2009/stardust.html
Sometimes, when we try to understand nature by carefully observing all of its occurrences, we may come across various phenomena both high above in the sky and right here on the ground or in water, right in front of our eyes. While some of these occurrences can be incredibly colorful and come in various unusual and interesting geometrical shapes, others can be quite extraordinary and even, entirely impossible to understand. We perceive these phenomena as rainbows, mirages or halos but the Earth has much more fascinating natural phenomena to offer us and some of these are the ones we are about to discuss in this article…
Undoubtedly one of the most beautiful events to occur in our world, the Northern Lights, also known as the Aurora Australis in the southern hemisphere, have always fascinated people and on the occasions that citizens of our planet have observed them, the sight has always filled them with awe. As the name suggests, these ethereal lights especially related to the Polar Regions. They occur most frequently in a belt of radius 2500 km centered on the magnetic north pole. This so-called auroral zone extends over northern Scandinavia, Island, the southern tip of Greenland and continuing over northern Canada, Alaska and along the northern coast of Siberia. In Norway, for instance, the Northern Lights can be seen every other clear night, if not even more frequently, while from southern Scandinavia, sightings would be only a few times a month and in central Europe hardly more than a few times a year. Moreover, there is also a documented fact that this phenomenon has even been seen from the Mediterranean but only a few times each century.
But what exactly are the Northern Lights anyway? According to Truls Lynne Hansen, the head of the Tromso Geophysical Observatory in Norway, the Lights stem from when large numbers of electrically charged particles at high speed stream in towards the Earth along its magnetic field and collide with the highest air particles. The air then lights up rather like what happens in a fluorescent light tube. The resulting colors reflect which gases we find up there, the most usual yellow-green color coming from oxygen, while red coloring is also due to oxygen but with a contribution from nitrogen. Another – violet color people often observe at the lower edge of the aurora is due to nitrogen, as is most blue coloring. The charged particles originate from the sun, and it is the “weather” conditions on the sun that decide whether or not we will see the aurora. Particles can stream out from the sun and some are captured by the Earth’s magnetic field and find their way into the Polar Regions. On the way, they travel out into the night side of the Earth and gain extra energy – but then he also adds that ‘we still lack understanding of exactly what happens out there!’.
Northern Lights
Yet another natural phenomenon that doesn’t require people to understand its origins but still manages to fascinate them just fine is known as Mammatus Clouds, or mammatocumulus, meaning “bumpy clouds”. This cellular pattern of pouches hanging underneath the base of a cloud, composed primarily of ice, can extend for hundreds of miles in each direction, while individual formations can remain visibly static for ten to fifteen minutes at a time. Despite popular misconception, they are not a sign that a tornado is about to form but true to their ominous appearance, mammatus clouds are indeed often indications severe weather has passed and thunderstorms are weakening. However, mammatus clouds sometimes form on the upwind, or backside, of heavy thunderstorms that at the same time are dropping large hail and unleashing strong bursts of wind but in most cases, mammatus can be found beneath the anvils of dying thunderstorms.
Mammatus Clouds
Let’s now move to water: more correctly known as an algal bloom, the so-called Red tide is a natural event in which estuarine, marine, or fresh water algae grow very quickly in the water column and can convert entire areas of an ocean or beach into a blood red color. This eye-capturing phenomenon is caused by high levels of phytoplankton accumulating to form dense, visible clouds near the surface of the water. 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. Several species are also dangerous for humans, and can cause symptoms ranging from discomfort to serious illness though no human exposure is known to have been fatal. Most nations keep a watch on their marine environments so that they can notify citizens when the water is unsafe due to a red tide.
Red Tide
Another interesting phenomenon is generally known as Penitentes due to its resemblance to processions of white-hooded monks. These amazing ice spikes, first described in the literature by Charles Darwin in 1839, can be found on mountain glaciers and vary in size dramatically: from a few centimeters to 5 meters in height. Initially, the sun’s rays cause random dimples on the surface of the snow. Once such a dimple is formed, sunlight can be reflected within the dimple, increasing the localized sublimation. As this accelerates, deep troughs are formed, leaving peaks of ice standing between them.
Penitentes
And finally, have you ever heard about the Sailing Stones? Yes, you’ve got it right- these are indeed the mysteriously moving stones of the packed-mud that can be found in the desert of Death Valley – the place that has been a center of scientific controversy for decades. Rocks weighing up to hundreds of pounds have been known to move up to hundreds of yards at a time. These are not ordinary moving rocks that tumble down mountainsides in avalanches, are carried along riverbeds by flowing water, or are tossed aside by animals. Some scientists have proposed that a combination of strong winds and surface ice account for these movements. However, this theory does not explain evidence of different rocks starting side by side and moving at different rates, in disparate directions and tracks are sometimes not linear. Moreover, the physics calculations do not fully support this theory as wind speeds of hundreds of miles per hour would be needed to move some of the stones. Isn’t that fascinating? You bet.
Sailing Stones
