ANOTHER SONDY GEOLOGICAL NATURAL WONDER By Wilton Strickland
About one mile due south of the parking ramp and control tower and across the Watson River at Sondrestrom Air Base (Kangerlussuaq), Greenland, is a small area laced with a "spider web" of small, shallow streams that constitute the outflow from Lake Ferguson. (Google Earth Kangerlussuaq) The area is on a plateau between the lake and the river and is covered with thick, low-growth tundra. Several times on warm and sunny Saturday or Sunday afternoons in the short summer of 1978, I walked around in the area of the streams enjoying the gurgling, cold, clear water as it rushes slightly down slope to the river. At the edge of the plateau above the river, the water cascades down a cliff-like bank, but, up on the plateau, the several streams are only a couple of inches deep and one can easily walk amongst them, step over them, etc. While walking amongst the streams, I noticed a very interesting phenomenon in the rock bottom of one of the streams - water was rushing in a rapid, counterclockwise swirl into a round hole in the bottom about one inch in diameter - a beautiful example and demonstration of the Coriolis effect, which causes fluids to flow in a drain or rise in a column (a tornado, for example) in a counterclockwise manner in the Northern Hemisphere and in the opposite direction in the Southern Hemisphere. The cone-shaped swirl was so perfect rushing into the hole, that I was able to tuck my finger deeply into the middle of the hole without getting it wet. I tried to disrupt the counterclockwise motion and make it swirl in a clockwise fashion by swirling my hand around the hole in a clockwise direction to force the water to reverse is direction of flow. I could get the swirl reversed, but it soon slowed and returned to its normal counterclockwise direction after I stopped swirling it with my hand.
Actually, Coriolis affects all objects, not only fluids, on Earth when they move from one point to another across the surface, within it and above it. This effect appears greatest when the object moves directly north or south. The effect and its apparent deflection of the moving object is caused by the Earth's rotation and its spherical shape which leads to the Earth's surface and objects on it having the highest west to east velocity at the equator; and decreasing as distance from the equator increases. This velocity at the equator is about 1,042 mph and decreases to zero at the poles. The entire Earth's angular velocity is 15° per hour, but due to its diminishing size as distance from the equator increases, the west-to-east surface velocity decreases accordingly. An airplane, or anything for that matter, moving North from any point, departs that point with the west-to-east, Earth-induced velocity of the point - faster eastward than the ground beneath it as it proceeds northward; it appears, therefore, to be deflected eastward (to the right in the northern hemisphere). An airplane, or anything, southbound in the Northern Hemisphere, has a SLOWER Earth-induced eastward velocity than the ground beneath it as it proceeds southward. The Earth beneath it is going eastward FASTER than the airplane's/object's Earth-induced velocity; the airplane/object, then, appears, relative to the Earth's surface, to be deflected to the right, again.
This same Coriolis effect is what causes hurricanes, typhoons, tornadoes, draining water, etc., in the Northern Hemisphere to rotate counterclockwise. Rising columns of warmer air in thunderstorms, any low pressure area of weather, draining fluids, etc., pull additional molecules of fluid horizontally to fill the space vacated by the vertical movement of fluids. Every molecule of fluid (air or water) in these situations that have any north-south component to its vector (direction and magnitude of movement) is deflected to the right in the Northern Hemisphere. (All of these directions are, of course, reversed in the Southern Hemisphere.) Though the apparent "force" on each molecule is infinitesimally small, the combination of them all produces the cyclonic, counterclockwise motion that can be extremely destructive and deadly when they form into a hurricane, typhoon or tornado.
Again, this apparent force applies to EVERYTHING moving from one point to another on, in, or above the Earth. It applies not only to airplanes and fluids in motion but also to balls, birds and bullets in flight and to our cars and bicycles as we drive or ride along; it even applies to a person walking or running. We never notice it, because "the force" (the apparent deflection) is so small and we constantly correct for it by maintaining contact, or repeated, cyclical contact with the Earth. 'Seems silly, but let's imagine and analyze a person's walk, for example: As the rear foot is moved forward, it has the west-to-east, Earth-induced velocity of the spot that it just departed. If the foot's vector has any north-south component, Coriolis deflects it ever so slightly to the right before it touches the Earth again. The deflection is so small we never notice it, unless one walks very fast and takes really big steps - big enough to produce an audible "chirp" like an airplane tire when the foot touches the ground, maybe? ;<)
Wilton
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