Paul Johnstone, age 10, of Quincy, I11., for his question:
HOW ARE GEYSERS FORMED?
Geysers are springs that throw up hot water with explosive force from time to time.They are formed near rivers and lakes where water drains through the earth deep below the surface. As part of a geyser,a deep channel reaches from the surface far into the earth. Cold water seeps down this channel until it reaches rocks that are very hot. Then it fills the channel and the water at the bottom is heated by the rocks. But the water in the channel cannot boil because of the weight of the column of water above it. Gradually, the heat at the bottom of the column rises far above the boiling point for water, and steam begins to form.
As steam forms, the rising bubbles lift the column a little, pushing some of the water in the channel over the opening onto the surface of the earth. That makes the column of water lighter and more water is able to turn into steam.
This building up of steam in turn lifts the column still more, until suddenly all the water near the bottom of the channel expands Into steam and forces out the rest of the water in a great steam explosion. After the water and steam settle back on the earth, some of the water seeps back into the earth and fills up the channel again. The crevices that feed the channel usually contain constrictions or sharp bends.This prevents connections which cause the water to mix in a uniform temperature. This mixing would keep the water from becoming superheated enough to explode into steam.
Geysers have often been compared with volcanoes, for they act similarly. But volcanoes shoot forth melted rock, while geysers erupt water containing dissolved mineral matter. After the eruption, the water evaporates or seeps back into the earth. The mineral deposits of some geysers form into weird castlelikeshapes and towers.
There are more than 200 active geysers in Yellowstone National Park. Two other famous geyser groups are found in lands extremely different from each other. One is in Iceland, known as the land of frost and fire. It is about 70 miles from Reykjavik, the capital, in the midst of barren lava fields.The other group of geysers is in the green countryside of New Zealand.
In Yellowstone's Upper Geyser Basin is the famous geyser called Old Faithful. It erupts on an average of every 65 minutes. The actual intervals between eruptions vary from about 30 to 90 minutes. Old Faithful sends a stream of boiling water more than 100 feet into the air.
Other geysers in the area include Castle, Giantess, Grand and Grotto. Morning Glory Pool, one of the most beautiful hot pools in the basin, resembles the morning glory flower in color and shape. Yellowstone's Norris Geyser Basin consists of hundreds of geysers, hot springs and pools. It is the hottest and most active thermal area in Yellowstone.The temperature of the water in some of the springs reaches more than 200 degrees Fahrenheit. Here Steamboat Geyser set a world record by hurling its water 400 feet into the air.