Why?

"Because it is there," said George Mallory, the British mountain-climbing pioneer. Arlene Blum has a different answer. The Himalayas certainly are there, but that's not what persuaded Blum to go for a nine-month, 2,000-mile walk last year across Bhutan, Sikkim, Nepal and India, from one end of the world's greatest mountain range to the other.

She did it, she says, because she wanted to develop a surer sense of direction, and what better way than by learning "how the Himalayas fit together"?

"In my formative climbing years, all I did was to try to keep my boyfriend's heels in sight," says Blum, 38, sitting lotus-style--and exceedingly erect--in the den of the official residence of her friend Martha E. Church, the trekker-president of Hood College, where Blum has just been telling awesome tales (accompanied by awesome slides) to an outdoorsy-looking audience unable to contain its "wows" and "goshes."

"When I started to do women's climbing, I did it in order to have a chance to lead," Blum says. She is a tall, ruddy-complexioned woman with a ready smile who wants it known that the word "great" in the name of her expedition--"The Great Himalayan Traverse"--refers to the mountain range rather than the feat.

She laughs nervously and admits to being "a little hyper" after her lecture. But she also speaks reverently of the Nepalese philosophy of "No hurry, no worry"--a way of life she thinks more Americans should get acquainted with.

She started climbing mountains as a student at Reed College in Oregon in the mid-'60s. The first time, "I just never felt happier. It was so beautiful!"

Her first non-male-accompanied climb was in Yosemite National Park in 1967, and while the mountain wasn't as hard as many she had tackled with her boyfriend, "it was more satisfying."

That same boyfriend, John Henry Hall, was crushed by an avalanche in 1971 while climbing Mount St. Elias in the Yukon Territory.

"I was terribly upset and went through a period of not climbing," says Blum. "And then I was even unhappier, because I had not only lost him but lost doing the thing I liked doing most."

So she took a sabbatical from her duties as a researcher and teacher of biochemistry at Berkeley, and went on a ferocious climbing tear that took her to Ethiopia, Kenya, Iran, Afghanistan and Nepal in the space of a year--and to the tops of several mountains that had never (to anyone's knowledge) been climbed before. Although Blum no longer felt "the same sense of unmitigated joy" about climbing, she soon set her sights even higher, planning an all-women's ascent of 26,540-foot Annapurna I, which had claimed the lives of one in 10 of all the climbers who had laid siege to it.

Blum has ambivalent feelings about the feminist statement made by an all-women's climb. She still resents the attitude that resulted in her exclusion from a climb in Afghanistan 14 years ago, when the expedition leader wrote her that "a source I trust has furnished a glowing account of your pleasant nature in the mountains. But one woman and nine men would seem to me to be unpleasant high on the open ice, not only in excretory situations, but in the easy masculine companionship which is so vital a part of the joy of an expedition."

The Annapurna expedition drew much of its financing from the sale of 15,000 T-shirts bearing the slogan: "A Woman's Place Is On Top." When Blum first saw that T-shirt, she laughed as hard as anyone. Still, she says, she would be happier if sex could be deleted from all discussion of mountain-climbing. "Individual differences are what count," she says. "I don't like making comparisons between men's and women's abilities, and I'm not sure that I recommend high-altitude climbing as a worthwhile endeavor for anyone."

For the 1978 Annapurna climb, Blum resolved to use Sherpa women as porters, although they traditionally did that type of work only at low altitudes. "At the time idealistically it seemed like the thing to do," she says. But the women in question showed little enthusiasm when Blum began training them as high-altitude porters, and in the end she had to settle for men--despite the objections of several expedition members who wanted no male involvement whatsoever.

Blum describes herself as an "overly conservative" leader who sees "every possibility of things going wrong." But her conservatism was not enough to prevent the deaths of two members of the Annapurna climb, Vera Watson and Alison Chadwick-Onyskiewicz, who insisted on going for the summit despite an unusually volatile avalanche situation and a dangerous lack of Sherpa support.

Blum herself decided to forgo the final ascent after six climbers barely had survived an avalanche that "swept from 24,000 feet to 18,000 feet in seconds."

She tried to dissuade Watson and Chadwick-Onyskiewicz, too, but they told her, "You know, we've risked our lives for weeks crossing the avalanches." And to complicate matters, the two women who already had reached the summit, Vera Komarkova and Irene Miller, supported Watson and Chadwick-Onyskiewicz in their desire to do the same.

"I never will know what would have happened if I had put my foot down and said 'No, you can't go,' " Blum says. "That's certainly something I thought about afterwards." She says this calmly, as if satisfied that she will never be able to refine the issues any further.

"I had hoped there would be a little more of a spirit of 'If anyone reaches the summit, there shouldn't be any need for others to go too.' I had hoped that women might have a greater sense of team spirit than men, but that isn't fair. Why should they?"

On predominantly male climbs (such as the 1976 Everest ascent in which Blum took part), the men play "summit politics," she says, racing each other from pinnacle to pinnacle to impress the leader. And Blum has found that women are not so different in this respect. In short, individualism is an essential element of the stuff that makes people climb mountains.

Since then, Blum has turned her attention from vertical to horizontal challenges.

When she became friendly with Hugh Swift, author of "The Trekker's Guide to the Himalaya and the Karakorum," they seized on the idea of walking the length of the Himalayas. They got their gear and clothing, free of charge, from L.L. Bean. "It was like Christmas," says Blum. "All our stuff was brand-new." They got much of their money from groups of tourist-trekkers who would join them on portions of their walk.

Given the duration of the journey, it may be just as well that, as Blum puts it, "we were kind of, sort of a couple." But these days, she and Swift are just good friends, and Blum says it has occurred to her that the relationship may have been generated by their common desire to walk through the Himalayas, rather than the other way around. "We're real different kinds of people," says Blum. "I like to walk and talk. He likes to walk alone."

The trip, which began in the heavily forested hills of Bhutan, took them over ridges as high as 19,000 feet above sea level and through valleys as low as 900. Along the way, they saw glorious green-terraced hillsides and bright red blossoms against austere gray-white peaks, heard the Dalai Lama deliver a speech, crossed perilous bridges, and ate a lot of rice and lentils, occasionally supplemented by freeze-dried treats and local meat and dairy products such as yak-milk, yak-yogurt, yak-cheese and tea with yak-butter.

Heading over a snow-filled pass one day, Blum was startled when a porter who also was a Brahmin priest suddenly sat down and announced he was going to die. Because of the snow and ice, he explained, he had been unable to wash his food in running water as his religion commanded. So he hadn't eaten for three days, and now he was starving--despite a heavy load of rice in his pack. "That's Nepal," says Blum. "It's a crazy place. People are very accepting of their fate."

The priest/porter recovered after being persuaded to eat some of Blum's packaged food. And the next day, with the snow behind them, he even said "Thank you"--a rarely used word in Nepali.

Border-crossings were another memorable trial. Going from Nepal into India, Blum and Swift had to walk an extra 22 miles because (despite prior clearance) a guard told them, "It is not permitted to cross here." And at the second crossing, the guard wanted to send them back to the first.

Blum also was struck by a severe toothache (despite a clean dental bill of health before her departure). This required a major detour to Darjeeling, where the only dentist for miles around filled up her ailing cavity.

But over all these adversities, she triumphed. And since her return, she has been busy setting up a series of commercial treks ("The Great Himalayan Treks") scheduled to begin this fall. The fees start at $1,500 (plus airfare), but no special physical conditioning is required. If a trekker starts slowly enough, according to Blum, trekking can be its own preparation.

And she hardly can wait to get back to the Himalayas. "I think I was meant to walk six hours a day uphill," she says.