Posts

Showing posts with the label geography

AMAZING FACTS ABOUT GEYSER

         A hot spring which at regular and irregular intervals thrown a jet of hot water and stream into the air; sometimes the jet rises to a heights of 100 to 200 feet. It occurs in a volcanic region.          From the mouth of the geyser, a tube penetrates deeply into the earth, and fills with water, which percolates through from the surface. The water near the base of this tube is considerably heated by hot lava, but the tube is long and narrow that convection cannot take place freely; the temperature of the water down below thus continues to rise, the boiling point of the water is relatively cool.      At the same time, the boiling point of the water at the base of the tube is raised by pressure, and the temperature has to reach well above 100 degrees centigrade before steam is formed. When this does take place, the water above is forced upwards and flows away. The sudden reduction of the pressure at the bottom of the tube lowers the boiling point of the water, and the

THE MYSTERIOUS DUST DEVIL

                                                     A local whirl of dust, usually not more than a few yards in diameter, in which the particles are swept round and round the centre, and are lifted to considerable heights –sometimes to 2,000 or 3,000 feet above the earth’s surface. It is caused by excessive local heating by the sun in an arid region, a strong convection current being formed. Dust devils usually move over the desert at from 5 to 15 miles per hour, though speeds of over 30 miles per hour are sometimes reached, and as many as five or six of them may often be counted by the observer. Being so limited in size, they are harmless even to aviation.       A storm in which a thick mass of dust obscures the atmosphere, and reduces visibility very considerably –sometimes practically to zero. It causes acute discomfort on the surface, and is a danger to aviation. It is caused by a turbulent wind blowing over an arid, dusty surface, and its approach is usually heralded by