Mount Katahdin Age | Granite Bedrock

Mount Katahdin | Baxter State Park | Millinocket, MaineMount Katahdin Age | Granite Bedrock… Yes, what is the age of Mount Katahdin? As Dee Caldwell points out in his study of geology of Baxter State Park in order to explain the age of Mt. Katahdin, a complete answer must cover three points:

First, Mount Katahdin’s age can be determined by the rocks that comprise the mountain are about 400 million years old. The bedrock is granite, gray at the lower and intermediate levels and pink at the higher ones, although lichen and weathering may obscure these colors. This like all granite’s, solidified from magma or molten rock below the earth’s surface. The Katahdin granite and its surface expression were part of a chain of volcanoes much like Mt. St. Helen’s and the Cascade Range, formed as tectonic plates collided. When the volcanic activity stopped, the top of the Katahdin magma chilled to a fine glass near its top, while magma below cooled slowly to form the coarse granite the occurs everywhere but the very highest elevations. From Pamola on the east to Baxter Peak and on to the western edge of the Tableland, there is a 500-foot-thick layer of very fine, extremely tough granite that crystallized from the glassy top. This tough rock, called the Summit granite, holds up the mountain. The Katahdin granite south of the mountain all the way to Jo-Mary has lost this resistant cap, eroding so much that it now underlies the West Branch and all the lakes and ponds.

A second way of asking Mount Katahdin’s age is to ask how long it has had its present general shape. The answer is two to five million years. Before that it was undoubtedly higher, rougher, and with a sharper profile, much like the western Rockies are today. But millions of years of erosion have worn Katahdin down to the top of the Summit granite.

A third answer to the question of Mount Katahdin’s age involves the specific features of Katahdin’s landscape, such as the Knife Edge, great and small basins, and the present attitude of 5,268 feet, all of which contribute so much to its fascination. Although Mount Katahdin was covered by one or more Mount Katahdin Wildlife - Deer | Baxter State Park | Millinocket, Mainecontinental glaciers (or ice sheets) during the various ice ages that have come and gone for the past million years, the distinctive features just mentioned were formed by the glacial action of comparatively small valley glaciers. Unlike the usual stream valley, which is V-shaped and narrow at its head, a glacial valley is U-shaped and widens into a bowl or basin at its head. This bowl is the cirque, and if the highland above the head-wall of a cirque is narrow enough, glacial action will eventually produce another striking geologic feature, an arête. This is the narrow strip of rock that results when the glacier eats away at the head-wall of its valley, until all that is left between it and the next valley is a ridge. The Knife Edge and Hamlin Ridge were both formed in this way. Since the last period of glaciation reached its peak only about 12,000 years ago, and since valley glaciers often remain active after continental glaciers have melted away, the answer to this third part of the question of age seems to be that Mount Katahdin isn’t very old at all—as geologic ages go, at least.¹

The Greatest Mountain

Mount Katahdin, the greatest mountain, lies within Baxter State Park. The Park was the result of Percival P. Baxter’s vision. Over 200,000 acres of mountains, lakes, streams and forest were given in trust to the people of Maine. He wanted to guarantee access to Maine’s wilderness and resources while preserving its’ unspoiled natural state. Baxter Peak (5,267′), the summit of Maine and northern end of the Appalachian Trail, is the highest point in Maine.

Charles Turner accomplished the first recorded climb in August of 1804. Today, Baxter Peak is the final goal of the hikers on the Appalachian Trail of their 2,100-mile journey. It is this journey from Georgia to Maine, which makes this destination the focus of Baxter State Park and Mount Katahdin.

Appalachian Trail ends on Mount Katahdin | Baxter State Park | Millinocket, MaineMount Katahdin has its share of recognition… it has been written about countless times, hikers have met their untimely end attempting to ascent its ruthless terrain, a steamboat was named after the esteemed Mountain as well as two U.S. Navy ships named USS Katahdin, even a song was composed as, “Mount Katahdin”.

The Park and Mountain region includes as an impressive variety of animals and unique plant life indigenous to its area. One needs to view and experience first-hand the wonders and beauty that exists in this region of Maine. Words cannot begin to describe the range of emotions experienced when in the midst of such natural beauty. Percival Baxter would be proud to see his dream being enjoyed, as he so wanted.

The Baxter State Park Authority website provides information on Camping and Reservations, Rules and Regulations, Hiking and Climbing Trails, Weather Conditions and Map of Baxter State Park. Should you like to learn about the Natural Setting and Scientific Forest Management Area—what is it?… you will find this information here.

MOUNT KATAHDIN ROCK FORMATION | BEDROCK

Is Mount Katahdin a volcano? 

There is a grain of truth to this myth, in that there are ancient volcanic rocks preserved nearby, in northern Baxter State Park, but none of the mountains of Maine’s modern landscape are actually volcano’s. Volcano’s are land-forms that were constructed by volcanic processes. All Maine’s mountains are erosional remnants. The rocks of Mt. Katahdin, in fact, are not volcanic rocks at all, but are granite, an igneous rock that forms by slow cooling of molten rock beneath the earth’s surface. It cannot be denied that the view of Mt. Katahdin from the northeast, with its bowl-shaped cirques carved by glaciers, superficially resembles that of a volcanic complex with summit calderas (compare with Mount St. Helen’s). The low-lying surrounding topography, underlain by more easily eroded sedimentary rocks, enhances the stand-alone effect.2

What is bedrock?

Bedrock is the solid rock that makes up the earth’s crust. It forms a continuous foundation beneath the whole state, but in most of Maine, bedrock is covered by some thickness of surficial sediments, soil, andAppalachian Trail ends on Mount Katahdin | Baxter State Park | Millinocket, Maine vegetation. Bedrock, or ledge, is commonly encountered in shallow excavation projects, such as digging for foundations or blasting for road construction. In addition, there are widespread natural exposures of bedrock on hilltops, where overlying materials have not accumulated, or along stream-beds and shorelines where bedrock has been washed clean. Maine has an abundance of boulders and stones in the glacial deposits that do not qualify as bedrock since they are no longer solidly attached below ground, but they can be just as troublesome for drilling and excavation projects.2

What kinds of rocks make up the bedrock of Maine?

Taken as a whole, Maine’s bedrock comprises a vast array of rock types, some common and some rare, each with variations in mineral content, color, texture, and structure. Geologists classify rocks and assign them names based on certain basic characteristics, but the degree of natural variation is almost limitless. All three major rock groups – sedimentary, igneous, and metamorphic – are represented in Maine.

Here is an abbreviated list of Maine rock types. Sedimentary rocks: shale, mudstone, siltstone, various sandstones, arkose, graywacke, chert, limestone, conglomerate. Igneous rocks (volcanic): basalt, andesite, dacite, rhyolite, various tuffs and breccias. Igneous rocks (plutonic): granite, pegmatite, quartz monzonite, syenite, diorite, diabase, gabbro. Metamorphic rocks: slate, phyllite, schist, granofels, various gneisses, marble, quartzite, greenstone, amphibolite, serpentinite, calc-silicate rocks, hornfels, migmatite, mylonite.2

How old is the bedrock of Maine? 

The oldest reliable age determined for a Maine rock is 647 million years old (with analytical uncertainty of 3.7 million years), for a pegmatite near Islesboro in Penobscot Bay. Interestingly, this pegmatite cuts Welcome to Baxter State Park | Mt Katahdin | Millinocket, Mainethrough rocks of the Seven Hundred Acre Island Formation, so we know that that formation is older than the pegmatite, but we don’t know by how much.

Individual mineral grains from the Chain Lakes massif, north of Eustis, have yielded a wide spectrum of ages, the oldest dated at about 2800 million years old (that’s 2.8 billion). These old grains are interpreted as a variety of sedimentary grains shed from an older continent and incorporated into a younger sedimentary rock. The rock itself is about 485 million years old. So, while this rock is not as old as the pegmatite in Penobscot Bay, it contains within it a few tiny mineral grains that are very old indeed.

The vast majority of Maine rocks are of Early Paleozoic age, from about 360 to about 510 million years old, representing 150 million years of earth history. Episodes of sporadic geologic activity occurred at younger times, producing relatively small amounts of igneous rock in restricted areas at around 290-300 million years ago, 200 million years ago, and 120 million years ago. The youngest bedrock known in Maine so far is a small igneous body in the town of Parsonsfield, the Randall Mountain stock, which has been dated at 104 million years old (with 4-million-year uncertainty).2

How did Maine’s mountains form?

Maine’s present landscape has formed primarily by erosion. Even the tops of mountains have bedrock that formed at depth in the earth and has been uplifted and eroded. Our mountains are simply places where the bedrock has been worn down less than the bedrock of the neighboring areas. Different rocks resist erosion to different degrees, depending on their composition, texture, and structure. This phenomenon, termed differential erosion, accounts for the main landscape features of geologically old mountain belts such as the Appalachians.2

Resource Links
Appalachian Trail Conservancy
Baxter State Park Authority
History of Baxter State Park
Maine Appalachian Trail Club
Mount Katahdin | Photos
Mt. Katahdin | Geography | History
Mt. Katahdin Peakware
More About Mt Katahdin
Native American Legends of Mt Katahdin
North Ridge, Traveler Mountain, Baxter State Park
Written in Stone
Katahdin Area Chambers
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¹Baxter Connie (1999). Greatest Mountain (Katahdin Wilderness). Tilbury House, Publishers Gardiner, Maine. ISBN 0-88448-213-8 (pbk.: akl. Paper). pp.9-10
2 Maine Geological Survey | Bedrock Geology FAQ

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