The Geology of Baxter State Park and Mt. Katahdin

Miscellaneous geologic features in Baxter State Park

Several features, not clearly related to either bedrock geology or glacial geology deserve mention.

Potholes

Bedrock outcrops in streams are often worn by pebbles and cobbles caught in swirling eddies. After many years of such wear a deep, smooth-sided hole, called a pothole, is worn in the bedrock. The best developed and most easily accessible potholes in Baxter State Park occur on Howe Brook, near South Branch Pond campground. These potholes, reached by a clearly marked trail, afford some of the most exciting, and undoubtedly, the coldest swimming in the State Park. Potholes are present on nearly every stream in the State Park (see Figure 1).

Streams and rivers

Parts of the courses of several streams in Baxter State Park are different from the courses used by those streams before the Katahdin area was glaciated. Some streams now flow in entirely different directions than they did prior to glaciation and some have taken over parts of other stream valleys. These changes may have been produced by glacial erosion, which opened new valleys through bedrock, or by glacial deposition which dammed the drainage, causing the stream to seek a new valley in which to flow; or by a combination of both glacial erosion and deposition. It will not be possible to mention all streams so affected, but the changes thought to have taken place in the Nesowadnehunk Stream valley will serve as a good example with which the interested reader may make his own reconstructions of drainage changes in other streams.

The small tributary stream just west of Doubletop Mountain flows northward until just above its juncture with Nesowadnehunk Stream, where it bends sharply to the south (see Plate 1). Such an orientation strongly suggests this tributary was once part of a north-flowing stream system and that it may once have drained into what now is Howe Brook. It is probably that this stream system comprised what is now the upper part of Nesowadnehunk Stream, Little Nesowadnehunk Stream, and the above mentioned tributary; that is, the part of the present drainage basin which is roughly north of Doubletop Mountain. Erosion by continental glaciers eroded the deep narrow valley east of Doubletop Mountain and glacial deposits blocking the former northerly outlet of the stream forced the drainage southward into the present course of Nesowadnehunk Stream. In other words, the present course of the stream from Doubletop Mountain northward is postglacial in origin, and now flows approximately in opposite direction of its preglacial course.

From the vicinity of Foster Field southward, Nesowadnehunk Stream flows in the valley of a smaller stream which probably flowed in much the same direction in preglacial times that it does now. Minor drainage changes which are mostly the result of glacial deposits may be noted in the downstream portion of Nesowadnehunk Stream. For example, Katahdin Stream probably used to be tributary to the preglacial lower Nesowadnehunk Stream, but has been diverted from the course by the prominent esker which occupies the valley in the vicinity of the Katahdin Stream campground.

Another characteristic of many streams in the Katahdin area which is related to glaciation is the presence in the stream channels of large numbers of extremely large boulders. Many of these boulders were transported to their present positions by glacier ice and even at highest flood stages the streams are incapable of moving them. Perhaps some boulders were deposited in the channels by streams having a great deal more water, and therefore possessing greater ability to transport large boulders. Such streams likely existed during the final melting of glacier ice and perhaps at times following glaciation during periods of greater rainfall than now prevails in the Mt. Katahdin area.

South Branch Pond delta

A delta is a deposit of sediments at the mouth of a river or stream. Between Upper and Lower South Branch Ponds there is a large, fairly level deposit of gravel and boulders which is a delta formed by Howe Brook (see Figure 15). Prior to the formation of this delta, the South Branch Ponds were one large lake.

The forested condition of the delta and the probability that the present Howe Brook, even at highest flood stage, is unable to transport most of the boulders on the delta, indicate that the delta was formed a long time ago. A good guess would be that it formed during the melting of the final remnants of the last continental glacier, when the glacial drainage channels (see Figure 15), which also indicate greater flow of water than presently occurs, also were probably formed.

Landslides

On many steep bedrock slopes which have a thin cover of till, the slopes have prominent landslide scars (see Figure 18). Landslides occur where loose material rests on slopes which are too steep, and are aided by heavy rain and meltwater from snow. Landslide scars on O.J.I. Mountain approximate the shape of those letters, but continued landslide activity has nearly destroyed the letters. Especially prominent scars occur on the east side of Doubletop Mountain.

Features related to climatic conditions

Above 4,000 feet elevation on Mt. Katahdin, the mean annual temperature is below 30°F and the climatic conditions are comparable to those found in the Arctic zone, 400 miles north of Mt. Katahdin. This severe climate has resulted in several interesting geologic and biologic phenomena.

Patterned ground

Figure 17

Curious rings of stones and bands of stones occur above timberline along many trails in Baxter State Park. These stone rings and stripes are called patterned ground and are formed by the expansion and contraction of the soil by freezing and thawing. Large stone rings, 20 feet or more in diameter, with boulders and cobbles on the margin, occur on the Tableland of Mt. Katahdin (Figure 17). Perhaps these rings formed during the severe climate when valley glaciers existed in the cirques below the Tableland. Miniature rings, a few inches in diameter and composed of small pebbles, are visible in the early spring along the Dudley Trail on Pamola but are destroyed by summer traffic, proving that miniature patterned ground features can form under the present climatic conditions. Other miniature patterned ground may be seen near the summits of many mountains in the Traveler Mountain region and along the shore of Grand Lake Matagamon at low water. Patterned ground is commonly associated with permanently frozen ground and occurs in such places as Siberia, northern Alaska, and northern Canada.

Rock streams

The boulder strewn slopes on the Tableland are not completely stable. The irregular streams of boulders indicate some slow movement downhill has occurred in the past and perhaps is still occurring on a small scale. The Saddle Trail from the Saddle to Baxter Peak and the upper part of the Cathedral Trail cross several of these rock streams (see Figure 2). Movement of boulders in these rock streams is a result of the steep slopes and is aided by the expansion and contraction of water as it freezes and thaws. Some material is carried by these rock streams to the steep cirque headwalls where rockslides and rockfalls occur.

Arctic plant and animal life

Mention of the present plant and animal life of Baxter State Park may be stretching the geologic nature of this paper, but as plants and animals are sensitive indicators of climate, the nature of such life above timberline in Baxter State Park deserves mention. Many species of shrubs, grasses, and heath plants which live on the Tableland are native to the Arctic zone and exist on Mt. Katahdin because of its severe climate. Several species of rodents and insects (not the ubiquitous black flies and no-seeums) which live on the Tableland are also natives of the Arctic zone.

Biologists feel that these plants and animals could not survive at lower elevations and it is an interesting problem as to how they got to Mt. Katahdin. Geologic evidence indicates that with each advance of the ice sheets the Arctic plants and animals migrated southward with the cooler climate. For example, reindeer and the wooly mammoth migrated as far south as Texas, where their fossil remains are now occasionally found. The melting of the ice allowed northward migration and those plants and animals which could not survive the warmer climate were killed off. Some plants and animals, however, had migrated to such areas as Mt. Katahdin, where the climate suited them and where they survive to this day - living remnants of a glacial climate. Mt. Washington and other of the White Mountains are also refuges for Arctic plant and animal life.

Patterned spruce and fir growth

Figure 18

On the slopes leading down into the large swampy area called the Klondike the spruce and fir growth has a curious striped pattern. This pattern is easily visible from almost anywhere on the Tableland or higher, but is especially prominent when viewed from the vicinity of Thoreau Springs, as shown in Figure 18 (see also Figure 12). In the original edition of this paper, following the consensus of local opinion, I described this pattern as blowdown formed during the 1938 hurricane. Several readers, including Dr. A. E. Brower of the Maine Department of Forestry, called my attention to several inconsistencies in this interpretation, not the least of which being that they had seen and photographed these features long before 1938. Dr. Brower also correctly pointed out that many of the trees in what appear to be areas of blowdown are still standing, although dead.

Although I still have no better explanation for this pattern than my original erroneous one, I have examined several of these bands of dead trees in detail. It appears that the trees in these patterns reach a certain age (between 50 and 100 years) or perhaps a certain height, then for some reason they die. Some time following their death, the trees are blown over and are systematically replaced by new growth. When this new growth reaches a certain height or age, it is killed in turn and replaced by other new growth. Thus this pattern is not the result of a single event, such as a hurricane, but is a constant process of death and replacement. But I have yet to find a reasonable explanation of how this whole process begins and why it should take the form of such well defined stripes.

It is well to leave this discussion of the geology of Mt. Katahdin with an unanswered question. Despite all that is known about the earth, there is probably much more that is not known. And the mystery of the curious striped pattern in the high spruce forests on Katahdin is only the most obvious of many questions yet to be answered.

Introduction Bedrock Glacial geology Geologic features Acknowledgments Glossary References Plates

Last updated on January 11, 2008

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