"The National Parks of the U.S.A." by James V. Murfin (Mayflower, illustrated with color photographs; 320 pages; $25).

This 9-by-12 1/2 volume is an unforgettable excursion through the 40 U.S. National Parks, from the Great Smokey Mountains and the Shenandoah to the incomparable Yosemite and the newly-founded Channel Islands.

The author, James V. Murfin, lives in Rockville, Md., with his wife and three children. He has been a writer and publications manager for the National Park Service 14 years. The book relects his personal observations in travels throughout the nation. He is the author of several other books, including "The Gleam of Bayonets" and "The Fields of Antietam" and numerous magazine articles.

The eruption of Mount St. Helens has told us -- "perhaps reminded us is better -- tragically, yet so vividly," he says, "that all is not yet done on this earth. The Colorado River slowly grinds away at the floor of the Grand Canyon, and at Bryce and Zion and Arches and the Canyonlands of Utah, the winds and rains inexorably carve and slice the landscape, but here the processes are extremely slow and these places have become attractions of beauty where changes are barely perceived from one generation to the next.

"The Badlands of the Dakotas, constantly changing now as in prehistoric times, indeed resemble the scientific descriptions of newly explored planets. Often called a vast wasteland, it is that only to men who tried and failed to tame what the Dakota Indians called mako sica; and the early French trappers called les mauvaises terres -- the bad lands.

"The earth is ever changing here. As the elements alter the Grand Canyon until someday only a plateau will remain, so the winds and rains and rivers will someday vanquish the strange and forbidding Dakota Badlands as they have done before. It is an unending process of erosion that moves so rapidly it alters from generation to generation.

"This was at one time, to put it in rather simplistic terms, the dumping ground for much of the West's erosion. Volcanic ash from the Yellowstone region fell from the westerly winds, and the waters of the highlands continued to deposit sediment.

"Gradually the climate changed. The mammals died, and with diminishing rains and dry north winds, grasslands replaced the marshes. Now the rivers, instead of building, carry away. Tributaries of the White River carve the soft sediment, exposing the remaining formations to the rain and wind, leaving bizarre, colorful spires, pinnacles, massive buttes and jagged ridges. Some life clings here and there, small islands of hope in an unfriendly landscape.

"Badlands National Monument was established in 1939 to preserve this unique scenery and to protect the great fossil resources and native prairie. The monument was elevated to national park status in 1978 . . .

"Oddly enough little was known about the interior structure of this land until 1951 when oil was discovered and debris from drilling began to yield the secrets of millions of years of land deposition.

"Theodore Roosevelt was only one of many who not only found beauty in this bizarre landscape but who invested in the productivity of the land. His sojourns in the 1880's and 1890's were brief, but through his prolific writings he introduced this little known and barely inhabited frontier to America.

"No other president has been so closely identified with the Dakotas. It was during his life here that he began to appreciate the need for the conservation of America's natural resources. Before being elected to the White House, he was instrumental in organizing the Boone and Crockett Club, dedicated to preserving this country's big game. And it was during these days that he warned that the nation was rapidly exhausting its forests faster than they were being produced."