Bobby Mann age 13, of Louisville, Ky., for his question:
What causes a geyser to erupt?
The largest geyser on record started to erupt in new Zealand in the year 1901, but its spectacular career lasted only two years. At its Peak, it spouted a bet of steamy water 1500 feet high, which is more than a quarter of a mile. It was a powerful squinter, and at one time it heaved a 150 pound boulder a distance of 1320 feet, which is exactly a quarter mile.
The world's geysers occur in regions where volcanoes have been active during the past few thousand years. In Iceland, where geysers are most abundant, the volcanoes are still active. But there are some 200 geysers in our Yellowstone Park, although no volcanoes have erupted here for the past several hundred years.
Nevertheless, we find geysers only where volcanic heat is trapped in the rocky layers deep below the surface. The top layer of a seething lava flow is exposed to the air and soon cools to form a crusty surface of solid, rock. This may prevent the heat from escaping by the lower levels. We are not certain of all the conditions necessary to form a geyser. It would be a dangerous job to dig down into the seething underground tunnels to make an on the spot examination.
But most experts agree that the necessary conditions include ground water, heated rocks at deep levels and buried cracks and crevices of a certain shape. There must be at least one sizable cavity lined with walls of hot rocks. There must be tubes leading to the surface, and these tubs must be angled to keep the heating water from boiling straight up from its seething cauldron.
Under normal air pressure, water boils at 100 degrees centigrade. But the boiling point rises as the pressure is increased. If a 100 foot column of water is being heated, the water at the bottom will not boil until it reaches 141+ degrees. The water at the bottom of a geyser, then, becomes far hotter than steam.
Water heats as it expands,. And at last some of the seething geyser water spills out of the cauldron. This releases the pressure on the hotter than hot water below. It turns to steam at once and up spouts the geyser with a foamy p1ume of steam and vapor and boiling water. Meantime., the buried cauldron is refilled with ground water and the process begins again.
Underground conditions are so varied that no two geysers are alike. Old Faithful can spit lip a p117me 120 feet high, and icelandts biggest geyser Sends up a fountain 10 feet wide and 200 feet high. Some geysers are tidy jets a few feet or just a few inches him. Some., like Old Faithful., erupt at fairly regular intervals., and sarne geysers erupt perhaps two or three times in one day and wait several days before putting on another show.