Dale Reynolds, age 11, of Coventry, Rhode Island, for his question:

What causes a dust bowl?

A disastrous dust bowl transforms vast areas of fertile earth into a desolate lunar landscape. Farms, fields and fences are knee deep in blowing piles of useless dust. The air is choked with dust and clouds of dust curtain the sun and the sky. Crops and grass cannot survive and there is no water for the thirsting cattle. As the land becomes useless, farmers and ranchers move elsewhere.

The United States has had more than its share of dust bowls and many people fear that we have not seen the last of them. Some blame the weather, some blame the ranchers and farmers. Both are partly right. Dust bowls are caused by long periods of drought or scanty rainfall, along with high winds. They are made worse by poor land management that strips the soil of well rooted vegetation.

We can do nothing about seasonal droughts that strike large areas of the continent from time to time. America's dust bowl is centered in and around the Texas Panhandle and Oklahoma. In this region of the Great Plains, seasonal rains are spotty and undependable and often the prevailing winds are strong and gusty.

For several years, perhaps a decade, there is enough rain to nourish miles and miles of healthy wheat and thriving ranchland. Then almost unnoticed, the rainfall diminishes year by year. Vegetation shrivels, the huge bread and beef region becomes a dust bowl, eroded by drought and drying winds. America's worst dust bowl struck in the 1930s. Another struck in the 1950s and another in the 1960s.

Before the farmers came, seasonal droughts are thought to have caused less severe dust bowls. Then the regions were covered with natural prairie grasses with short tops and long tangled roots. Winter and summer, rain and drought, this hardy vegetation anchored down the top¬soil, reducing erosion and blowing dust.

When the region was cultivated, some of it became ranchland and some was plowed for annual wheat crops to feed a hungry world. During the moist seasons, it became a huge rich bread and beef basket. Nobody noticed that crowded cattle stripped the earth bare, or that the roots of annual cereal grains failed to anchor the topsoil. ,

Dry seasons began early in the 1930s. Patches of bare soil crumbled to dust and dry winds shifted the dust from here to there. Soon vast areas of farmland were knee deep in blowing dust and eventually 50 million acres became a dust bowl. e

Nowadays, farmers practice contour plowing to hold back erosion and ranchers keep smaller herds on their acreage. Modern cereal grains have stronger root systems and miles of trees have been planted to act as screens in the path of the prevailing winds. Droughts that cause dust bowls will come again, but good land management will prevent them from being so severe.