High Peaks

An anorthosite outcrop near Jay, NY.

Photograph by. L. Gillett, c. 1999.

Geology

The Adirondack Mountains are underlain by Grenville-aged (ca. 1 billion years before present), high-grade metamorphic rocks. The High Peaks region, which contains many peaks with summits greater than 1,200 meters (ca. 4000 ft) above sea level, is generally underlain by anorthosite and related rocks. Anorthosite is a plutonic igneous rock that consists of more than 90% plagioclase feldspar with varying amounts of accessory minerals such as amphibole, pyroxene, iron-titanium oxides, and garnet.

Anorthosites are relatively uncommon rocks. With very few exceptions, anorthosites formed between 1.45 to 1.10 billion years before present, suggesting that some unique event in Earth history occurred during that time span. Their geographic distribution is limited, but where they occur they are found in large masses. The Mount Marcy anorthosite body occupies more than 8,000 square kilometers (3,300 square miles) and is the largest single anorthosite body in the United States.

Anorthosites also have economic importance. They are often associated with iron-titanium ore deposits, such as the ilmenite ore deposits at Tahawus in the south-central High Peaks region. Anorthosites are also used as dimension stone. Lake Placid Granite distributes anorthosite worldwide from its quarries near Ausable Forks.

The combination of steep terrain and thin soils create spectacular waterfalls and make Adirondack slopes susceptible to landslides. Heavy rainfall associated with the remnants of Hurricane Floyd in September, 1999 created many new slides in the High Peaks region. The largest of these can be found on Mount Colden, Algonquin Peak and Wright Peak. Debris from the Colden slide forced the temporary closure of trails though Avalanche Pass in the High Peaks Wilderness.

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Rainbow Falls.
photograph by D. Franzi, c.1999

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The Macomb Mt. landslide.
photograph by D. Franzi, c.1999

Ecology

The High Peaks Wilderness encompasses more than 87,000 hectares (215,000 acres) in the Adirondack Mountains. Northern hardwoods cover most of this region, especially on sites with fertile, well-drained soils and low to intermediate slopes. The dominant tree species in the northern hardwood forests are sugar maple, American beech, and yellow birch. Dense patches of the shrubby plant, hobblebush, are common. Chipmunks, wood frogs, ovenbirds, wood pewees, and black-throated blue warblers can be seen and heard in these woods.

Above an elevation of approximately 760 meters (2,500 ft) on the mountain slopes, northern hardwood species become less dominant and are replaced by conifers, especially red spruce and balsam fir. In areas that have been disturbed by fire or blowdown, balsam fir can be seen growing beneath aging stands of white birch. Wild flowers such as bunchberry, and goldthread become more abundant on the forest floor at this elevation. Red squirrels, boreal chickadees, and black-throated green are active and vocal in this forest zone.

Between 1,280 and 1430 meters (4,200 and 4,700 ft) elevation, the mineral soil becomes shallow and a thick layer of organic material covers the bedrock. Red spruce cannot survive under these conditions and the forest is primarily balsam fir. Above this elevation, the fir trees, along with black spruce, appear dwarfed and wind-shapen. This is the krummholz or "twisted-tree" zone.

The krummholz zone on Algonquin Peak.
Photograph by D. Franzi, c.1997

Timberline in the Adirondacks is near the 1,490 meter (4,900 ft) elevation. Here, the alpine zone of open mountain summits is home to tundra vegetation and a place for great scenic vistas! With only about 85-acres of alpine tundra in New York, scattered across some 20 high peaks, these ecosystems are truly "islands in the sky" that need protection. Plants of the alpine tundra are adapted for survival under extreme climatic conditions but the impact of hikers' boots. Do the "rock-walk" as you enjoy the views from the mountain tops in New York. At your feet, you will find low-growing, mat-like wildflowers such as diapensia, three-toothed cinquefoil, and mountain sandwort.

Deer's hair sedge in autumn, Mount Marcy is in the right background.
Photograph by Ken Adams, c. 1999.

The photographs below depict some of the alpine vegetation that you are likely to encounter in the alpine zone. Dark-eyed juncos and white-throated sparrows are common birds here. Keep on the lookout for ravens and perhaps even a peregrine falcon!


Mountain sandwort. Photograph by D. Franzi, c.1997	Prostrate bearberry willow on Algonquin Peak. Photograph by D. Franzi, c.1997


Star flower. Photograph by D. Franzi, c.1997	Deer hair and prostrate black spruce in early summer (compare to deer hair photograph above). Photograph by D. Franzi, c.1997