The Adirondack Mountains /ædɪˈrɒndæk/ form a massif in northeastern New York, United States. Its boundaries correspond to the boundaries of Adirondack Park. The mountains form a roughly circular dome, about 160 miles (260 km) in diameter and about 1 mile (1,600 m) high. The current relief owes much to glaciation.
The earliest written use of the name, spelled Rontaks, was in 1724 by the French missionary Joseph-François Lafitau. He defined it as tree eaters. In the Mohawk language, Adirondack means porcupine, an animal that may eat bark. The Mohawks had no written language at the time so Europeans have used various phonetic spellings. An English map from 1761 labels it simply Deer Hunting Country and the mountains were named Adirondacks in 1837 by Ebenezer Emmons.
People first arrived in the area following the settlement of the Americas around 10,000 BC. The Algonquian peoples and the Mohawk nation used the Adirondacks for hunting and travel but did not settle. European colonisation of the area began with Samuel de Champlain visiting what is now Ticonderoga in 1609, and Jesuit missionary Isaac Jogues visited the region in 1642.
In 1664 the land came under the control of the English when New Netherland was ceded to The Crown. After the American Revolutionary War, the lands passed to the people of New York State. Needing money to discharge war debts, the new government sold nearly all the original public acreage about 7 million acres for pennies an acre. Lumbermen were welcomed to the interior, with few restraints, resulting in massive deforestation.
For the history of the area since industrialization, see The History of Adirondack Park.
The rocks of the Adirondack mountains originated about two billion years ago as 50,000 feet (15,000 m) thick sediments at the bottom of a sea located near the equator. Because of continental drift these collided with Laurentia (the precursor of modern North America) in a mountain building episode known as the Grenville orogeny. During this time the sedimentary rock was changed into metamorphic rock. It is these Proterozoic minerals and lithologies that make up the core of the massif. Minerals of interest include:
Note that even though they all resulted from the Grenville orogeny, neither the Adirondacks (now uplifted by a hot spot) nor the Catskills or Poconos (a dissected plateau formed from delta deposits) are part of the Appalachian Mountain chain (faulted and folded by continental collisions).
Around 600 million years ago, as Laurentia drifted away from Baltica (European Craton), the area began to be pulled apart forming the Iapetus Ocean. Faults developed, running north to north east which formed valleys and deep lakes. Examples visible today include the grabens Lake George and Schroon Lake. By this time the Grenville mountains had been eroded away and the area was covered by a shallow sea. Several thousand feet of sediment accumulated on the sea bed. Trilobites were the principal life-form of the sea bed, and fossil tracks can be seen in the Potsdam sandstone floor of the Paul Smiths Visitor Interpretive Center.
About 10 million years ago the region began to be uplifted. It has been lifted about 7000 feet (2100 m) and is continuing at about 2 millimetres per year, which is greater than the rate of denudation. The cause of the uplift is unknown, but geologists theorize that it is caused by a hot spot in the earth's crust. The occurrence of earthquake swarms near the center of the massif at Blue Mountain Lake may be evidence of this. Some of the earthquakes have exceeded 5 on the Richter magnitude scale.
Starting about 2.5 million years ago a cycle of Pleistocene glacial and interglacial periods began which covered the area in ice. During the most recent episode, the Laurentide ice sheet covered most of northern North America between about 95,000 and c. 20,000 years ago. After this the climate warmed, but it took nearly 10,000 years for all of the 10,000 feet (3,000 m) thick layer of ice to melt. Evidence of this period includes:
Soils in the area are generally thin, sandy, acidic, and infertile, having developed since the glacial retreat.
The Adirondack Mountains form the southernmost part of the Eastern forest-boreal transition ecoregion. They are heavily forested, and contain one of the southernmost distribution taiga in North America. The forests of the Adirondacks include spruce, pine and deciduous trees. Lumbering, once an important industry, has been much restricted by the creation of the park.
Nearly 60 percent of the park is covered with northern hardwood forest. Above 2600 feet (790 m) conditions are too poor for hardwoods to thrive, and these trees become mixed with or replaced by balsam fir and red spruce. Above 3500 feet (1000 m) black spruce replace red. Higher still only trees short enough to be covered in snow during the winter can survive.