Joan Wilson, age 13, of Ottawa, Ontario, Canada, for her question:

What is the meaning of permafrost?

The word may lead your thoughts to the shivering conditions inside a permanently frozen deep freeze unit. But permafrost is a geological term belonging to ecologists and earth scientists. It refers to a ground condition almost as severe as the inside of a deep freezer.

In polar regions, the summer sun stays above the horizon for much of the time. But despite the long hours of sunshine, the polar summer is not as warm as midsummer in the tropics and temperate zones. And the polar summer day is followed by a polar winter night in which the sun scarcely rises above the horizon for months at a time. This type of climate creates a ground condition known as permafrost.

The Antarctic is a region of perpetual winter and much„of the ground remains buried year round below a massive icecap. Here; permafrost occurs only on a few favored shores and islands. It also occurs in a few Alpine regions of the temperate zones. But the earth's major permafrost region is within the Arctic Circle, in those areas where the icy accumulations of the long winter do melt for a few short months to expose the ground to the warming sun. This northern permafrost region covers an area of five million square miles, which is one tenth of the earth's total land.

Here the ground is permanently frozen to an average depth of 1,600 feet. The summer sun bestows only enough warmth to melt the topmost layers of the frozen sur¬face. The average yearly precipitation is about eight inches, and the Arctic climate is rated as a desert. But under the summer sun, the ground yields up a lot of its frozen moisture and this so called tundra becomes a region of ponds and puddles, soggy bogs and streams. This harsh region renews our faith in nature's undefeatable determination to support life wherever and whenever possible.

Tree roots cannot pierce the hard, icy ground, but in summer the thin surface layer of thawed earth and watery moisture produces an abundance of low growing plants. In a few sunny months, hundreds of species sprout up, blossom and produce seeds to survive through the cruel winter. In spring, vast patches of the permafrost are covered with floral carpets of rainbow colors. As summer turns to fall, the low growing foliage turns to autumn tints embroidered with clumps and clusters_of vivid fruits and berries.

Bright lichens adorn the barren rocks and the boggy swamps are choked with peat mosses and hummocks of tough Arctic grass.

Wherever there is plant life, animal life arrives to feed upon it. Lemmings crowd into burrows below the surface and herds of caribou trek north to graze on the summer vegetation. Countless waterfowl arrive to nest near the soggy ponds and gorge on the teeming fishes in the streams. Countless land birds fly north to nest on the ground where there is plenty of plant food and ;swarms of summer insects to feed their families. Most of these summer residents depart long before winter's icy grip returns to the treeless tundra.

Agriculturists view the vast permafrost area as a total wasteland. Bacteria are needed to create loamy layers of fertile soil, and few of these busy midgets can abide long periods of frost. In the stagnant puddles, sphagnum mosses create acid conditions that are unfriendly to bacteria and to many plants. Soil formation is slow and shallow. The frost tends to shift and shuffle the surface, and areas of established plants are uprooted every 50 years or so. Meantime, wind and water carry seeds and spores to clothe other frost scarred areas of the tundra.