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Adirondack Geology: Old Rocks and New Mountains: Glenn A. Richard. The Adirondacks are a dome of old rock (1.1 billion years), surrounded by much younger rock (less than 600 million years). Relief Map of Adirondacks. Map of Streams and Lakes.
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Glenn A. Richard
The Adirondacks are a dome of old rock (1.1 billion years), surrounded by much younger rock (less than 600 million years)
Relief Map of Adirondacks
Surface water elevations are primarily controlled by underlying bedrock elevations, rather than the type of bedrock.
Radial drainage pattern:
Streams flow primarily outward from the center toward the edge.
However, drainage in the Adirondacks is also controlled by faults.
Roadless areas are undeveloped. ~43% of 6 million acre Adirondack Park (created in 1892) is owned by the state and belongs to the Forest Preserve (created in 1885).
Mount Marcy, highest point in New York (5344’), from Haystack. Predominant rock type is metanorthosite (Mineralogy: mostly blue labradorite feldpar (high in Ca, some Na, low in K), with some pyroxene).
Shore of Lake Champlain (elevation 95 feet) from eastern Adirondacks. Lowest elevation in Adirondacks.
Haystack from Marcy – July 2, 2001. Rugged topography caused by faulting, uplifting, erosion by water and glacial ice.
Picea rubens and Abies balsamea just below tree line on Haystack, third highest peak in the state at 4960’.
Diagram by Keelin Murphy
Crust and very upper mantle are hard rock, called lithosphere.
Lithosphere divided into tectonic plates. Plates are in motion – several centimeters per year – PLATE TECTONICS
Orogeny: Collision of plates can build mountains (Example: Himalayas now rising due to current collision of Indian and Asian plates).
Transform: San Andreas Fault
Divergent: East Pacific Rise
Convergent: West Coast of South America -Andes forming here
Fossil stromatolite (blue-green alga, 1.3 bya) near Balmat in western Adirondacks. From Pre-Grenville Ocean prior to Grenville Orogeny .
Metanorthosite (intruded about 1.15 bya) with labradorite crystal on Noonmark. Smaller amounts of pyroxene are present.
Grenville Orogeny metamorphosed the rock about 1.1 bya while it formed the Grenville Supercontinent and the Grenville Mountains.
Boudinage in migmatite, northwestern Adirondacks formed during Grenville Orogeny 1.1 bya
Lake Placid from Whiteface. Shape is controlled by a group of faults that formed about 650 million years ago, when Grenville Supercontinent split up.
Colden, Avalanche Pass, Algonquin, Indian Pass, Wallface. Passes are valleys formed along faults.
Lake Placid from Whiteface. Shape is controlled by some of the faults that formed about 650 million years ago.
Diabase dike (650 mya) in western Adirondacks intruded during breakup of Grenville supercontinent.
Ripple marks on Potsdam Sandstone (500 mya), Ausable Chasm display. Formed in warm shallow sea. Potsdam sandstone probably covered Adirondacks and was eroded from central portions after later uplift.
Great Range from Noonmark – Adirondacks rising since 60 to 15 million years ago for uncertain reasons. Some have attributed uplift to a hot spot, but there is not much evidence for that.
Glacial erratic near Debar Mountain in northern Adirondacks
Au Sable Chasm with Potsdam Sandstone. Au Sable River has cut into the sandstone as uplift occurs.
Snow on Saint Regis Mountain with fall color at lower elevations, shows climate variation with elevation.
Red oak at Lake Champlain shore. Soil in Adirondacks is mostly acid.
Walking fern near Lake Champlain shoreline favors habitats where calcite is present.
Cystopteris bulbifera at Cascade Lakes favors habitats where calcite is present.
Cotton grass on floating bog mat at Sunday Pond. Peat is acidic and water is low in oxygen and dissolved nutrients
Insectivorous pitcher plant on Sunday Pond bog mat. Bog water is low in nitrates.
Altona Flat Rock with Potsdam Sandstone – Pine barrens on very thin soil. Soil washed away by catastrophic flood during glacial times.
Pteridium aquilinum in Clintonville Pine Barrens grows well in dry, sandy, acidic soil.
Bearberry in Clintonville Pine Barrens gows well in dry, sandy, acidic soil.
Haystack Summit (4960’) – Very thin soil and cool conditions above treeline support alpine plant community.
Black crowberry (green) and mountain bilberry (red) on Noonmark in October
1.3 Billion Years Ago – Warm shallow pre-Grenville Sea
1.1 Billion Years Ago - Grenville Orogeny
650 Million Years Ago – Grenville Supercontinent breaks up
500 Million Years Ago – Warm shallow sea, Postdam Sandstone
60 to 15 Million Years Ago – Adirondacks begin to rise
1.6 Million Years Ago – Ice Ages begin