Published on 4/28/2009
under Science
- by Gracie Murano
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Aurora Borealis
Undoubtedly one of the most beautiful events to occur in our world, the Aurora Borealis, also known as the Northern Lights, has both astounded and amazed people since it was first discovered. This phenomenon ocurrs when the sun gives off high-energy charged particles (also called ions) that travel out into space at speeds of 300 to 1200 kilometres per second. A cloud of such particles is called a plasma. The stream of plasma coming from the sun is known as the solar wind. As the solar wind interacts with the edge of the earth’s magnetic field, some of the particles are trapped by it and they follow the lines of magnetic force down into the ionosphere, the section of the earth’s atmosphere that extends from about 60 to 600 kilometers above the earth’s surface. When the particles collide with the gases in the ionosphere they start to glow, producing the spectacle that we know as the auroras, northern and southern.
Mammatus Clouds
Also known as mammatocumulus, meaning "bumpy clouds", they are a cellular pattern of pouches hanging underneath the base of a cloud. Composed primarily of ice, Mammatus Clouds can extend for hundreds of miles in each direction, while individual formations can remain visibly static for ten to fifteen minutes at a time. True to their ominous appearance, mammatus clouds are often harbingers of a coming storm or other extreme weather system.
Red Tides
More correctly known as an algal bloom, the so-called Red tide is a natural event in which estuarine, marine, or fresh water algae accumulate rapidly in the water column and can convert entire areas of an ocean or beach into a blood red color. This phenomena 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. 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.
Penitentes
These amazing ice spikes, generally known as penitentes due to their resemblance to processions of white-hooded monks, can be found on mountain glaciers and vary in size dramatically: from a few centimetres to 5 metres 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.
Sailing Stones
The mysterious moving stones of the packed-mud desert of Death Valley have 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. 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 and in disparate directions. 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.
Supercells
Supercell is the name given to a continuously rotating updraft deep within a severe thunderstorm (a mesocyclone) and looks downright scary. They are usually isolated storms, which can last for hours, and sometimes can split in two, with one storm going to the left of the wind and one to the right. They can spout huge amounts of hail, rain and wind and are often responsible for tornados, though they can also occur without tornados. Supercells are often carriers of giant hailstones and although they can occur anywhere in the world they’re most frequent in the Great Plains of the US. (photo by Mark Humpage)
Fire Whirls
A fire whirl, also known as fire devil or fire tornado, is a rare phenomenon in which a fire, under certain conditions --depending on air temperature and currents--, acquires a vertical vorticity and forms a whirl, or a tornado-like effect of a vertically oriented rotating column of air. Fire whirls often occur during bush fires. Vertical rotating columns of fire form when the air currents and temperature are just right, creating a tornado-like effect. They can be as high as 30 to 200 ft tall and up to 10 ft wide but only last a few minutes, although some can last for longer if the winds are strong.
Ice Circles
A rare phenomenon usually only seen in extremely cold countries, scientists generally accept that Ice Circles are formed when surface ice gathers in the center of a body of water rather than the edges. A slow moving river current can create a slow turning eddy, which rotates, forming an ice disc. Very slowly the edges are ground down until a gap is formed between the eddy and the surrounding ice. These ice circles have been seen with diameters of over 500 feet and can also at times be found in clusters and groups at different sizes.
(Photo by Brook Tyler)
Gravity Waves
The undulating pattern of a Gravity Wave is caused by air displaced in the vertical plain, usually as a result of updrafts coming off the mountains or during thunderstorms. A wave pattern will only be generated when the updraft air is forced into a stable air pocket. The upward momentum of the draft triggers into the air pocket causes changes in the atmosphere, altering the fluid dynamics. Nature then tries to restore the fluid changes within the atmosphere, which present in a visible oscillating pattern within the cloud.
(Photo by: NASA)
Hums
"The Hum" is the common name of a series of phenomena involving a persistent and invasive low-frequency humming noise not audible to all people. Hums have been reported in various geographical locations. In some cases a source has been located. A well-known case was reported in Taos, New Mexico, and thus the Hum is sometimes called the Taos Hum. They have been reported all over the world, especially in Europe: a Hum on the Big Island of Hawaii, typically related to volcanic action, is heard in locations dozens of miles apart. The Hum is most often described as sounding somewhat like a distant idling diesel engine. Difficult to detect with microphones, its source and nature are unknown.
Aurora Borealis
Mammatus Clouds
Red Tides
Penitentes
Sailing Stones
Supercells
Fire Whirls
Ice Circles
Gravity Waves
Hums
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7 Incredible Natural Phenomena you've never seen
