periodic, which does not mean quite the same thing. In Glacier 

 Bay this phenomenon has now been watched for over 250 years. 

 In 1700 the whole of the bay was clogged with solid ice about 

 three thousand feet thick extending almost to its mouth in Icy 

 Strait. Thereafter the ice apparently began to melt faster than it 

 formed, and this process continued till the end of the nineteenth 

 century. Then, in 1899, a violent earthquake seems to have 

 shaken the whole area, and this is said to have sneeded the 

 break-up and retreat of the ice. These effects were short-lived, 

 but the steady retreat went on, so that by 1913 the Muir Glacier 

 had retreated eight miles from the coast and by 1946 another 

 five miles. 



The speed of this change, whether it be permanent or only 

 temporary, should give us pause. The fact that fifty miles of 

 solid ice three thousand feet deep can completely vanish in a 

 little over a hundred years, and then vast glaciers that once 

 formed parts of them retreat another ten miles or more over- 

 land in a further century, should make us reappraise our ideas 

 about icecaps and so-called ice ages. This is probably the single 

 most important aspect of nature as regards not only the past and 

 the present but also the future, for everything that we see on 

 this continent — and, for that matter, throughout the world — is 

 ultimately controlled by changes in the volume and distribution 

 of polar ice. 



That almost all parts of the land surface of the earth have at 

 one time or another been covered with icecaps is now well 

 established. Even areas such as the Congo and the Indian or 

 Deccan Peninsula, which now lie in the tropics, have been so 

 covered. Northwestern Europe and northeastern North America 

 were covered, as it now appears, until only ten thousand years 

 ago. However, since it is undeniable that plants and animals 

 that cannot live or breed in polar conditions of temperature and 

 more especially of light are found fossilized not only all around 

 but well within both polar regions, as they are today, the land 

 or sea where those animals once lived must at one time have 

 been somewhere else on the earth's surface where it was warmer 

 and where sunlight was more evenly distributed throughout the 

 year. Thus, the land must have moved in and out under the polar 

 ice, rather than the polar icecaps over the land. 



The last movement that presumably brought on the current 

 series of so-called ice ages was, until recently, supposed to have 

 taken place about a million years ago, initiating what is called 

 the Pleistocene Period of geological history. Since then, there 

 have been four marked climatic swings in both northern Europe 

 and North America, and these have been marked by the for- 

 mation of large icecaps on these continents. The centers of these 

 icecaps do not seem to have been in the same place, but as we 

 have seen, the last one on this continent appears to have been 

 in Hudson Bay. In addition to these major climatic and tem- 

 perature swings, which may have been brought about by such 

 processes as the blocking of warm water from the Arctic Ocean 

 and so forth, there have also been numerous minor swings in 

 temperature, as evinced by the behavior of these Alaskan glaciers 

 during the past 250 years. There is no evidence that these are 

 caused by movements of the crust, but they do bring us to 

 another aspect of the problem — namely, the time factor. If fifty 

 miles of ice three thousand feet thick can vanish in a couple of 

 centuries (and at high latitudes at that), how quickly, we would 

 like to know, can large icecaps "retreat" or the land shift? 



The last icecap we had on this continent changed just about 

 everything from climate to soils, plant and animal distribution, 

 rivers, lakes, and deserts. Perhaps forty days and forty nights of 

 snow or rainfall could bring on an "ice age " or a flood. We do 

 not know, but in Glacier Bay National Park you may look 



around and ponder these matters with gigantic visual aids all 

 about you. Two hundred and fifty years is nothing, cosmically 

 speaking, yet a fifty-mile icefield vanished from here in that 

 time. What is more, vegetation has appeared again and forests 

 are growing where a mile of ice was before. And that there 

 were great forests there before the ice came is also proved by 

 the endless tree stumps that are bulldozed out of the moraines 

 left by ancient glaciers. 



THE COMPLEXITY OF BEARS 



The forests on the southern coast of this province are, as we 

 mentioned above, moss-festooned "jungles" of spruce and hem- 

 lock with a vast tangle of alders and ferns below. This supports 

 a marvelously rich fauna. There is even a salamander found here 

 (by the name of Batracochosepsj, a weird, immensely elongated 

 thing like a worm with tiny limbs. There are two species of frogs 

 and a plethora of insects. Birds are everywhere — ducks, geese, 

 loons, cormorants, eider ducks, gulls, murrelets, puffins, and 

 guillemots about the waters, and falcons, eagles, ravens, and 

 ptarmigan on shore. There are even hummingbirds from spring 

 to late fall — something that is more than merely surprising. The 

 mammalian fauna is almost as varied. On the mountains are 

 the famous white or Dall's sheep, which unfortunately also come 

 in three other color phases — brown, gray, and black — moun- 

 tain goat, black-tailed deer, wolverine, red fox, marten, mink, 

 porcupine, and both bobcat and lynx. But above all there are 

 the bears. 



There are three kinds of bears on this continent — the Polar 

 Bear (Thalarctos): the "Black" or American Bear (Euarctos): 

 and the Dish-faced or "Brown" Bears (Ursits). There is one or 

 just possibly two species of the first, as discussed above; one 

 of the second, with several color phases and two or three appar- 

 ently stable varieties; and today, two major groups of the last. 

 If you want to understand the bears, or know just what you are 

 looking at if you are wandering about in Alaska, the first thing 

 you have to do is forget all references to color in bears. This 

 means that "black," "brown," "blue," "cinnamon," "grizzly." and 

 "white" are not only redundant terms but misleading. Although 

 there are plenty of bears alive today that may be described as of 

 these colors, there are no such things specifically as Black, Brown, 

 Blue, Cinnamon, Grizzly, or White bears. These are merely color 

 phases, any and sometimes all of which may turn up among 

 either American Black or Dish-faced Bears, very often in twins 

 in the same litter. 



There were once races of pure-breeding dish-faced bears of 

 huge size, with grizzled pelts; these dwelt on the central prairies 

 and fed on the bison herds. They are now extinct. However, 

 there remain in some parts of the western montane regions and 

 in British Columbia, the Yukon, Alaska, and the Great Bear 

 Lake district of the Canadian Northwest Territories, sundry 

 races of grizzled bears belonging to the Dish-faced or "Brown" 

 bear group. When grizzled, these may be referred to legitimately 

 as Grizzly Bears, but it must be stressed that these do not neces- 

 sarily breed true to color nor even stay the same shade individ- 

 ually from year to year. 



The big Dish-faced or true "Brown" Bears — related to those 

 of Asia and Europe — form a rather well-knit group that are 



The Valdez Glacier flowing into Prince William Sound from 

 the Chugach Mountains. This is a classic "ice river," flowing 

 strongly but generally recedittg, and carrying much debris. 



