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 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 million acre Adirondack Park (created in 1892) is owned by the state and belongs to the Forest Preserve (created in 1885) Roads 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 Gothics – September 2, 2001- Note steep rockslides Picea rubens and Abies balsamea just below tree line on Haystack, third highest peak in the state at 4960’ Cross section of Earth Layers of the Earth: Diagram by Keelin Murphy •Inner Core •Outer Core •Mantle •Crust 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) Cornus canadensis on Crane Mountain On August 17, 2000 Altona Flat Rock with Potsdam Sandstone – Pine barrens on very thin soil Soil washed away by catastrophic flood during glacial times Clintonville Pine Barrens on sandy glacial outwash State-rare Ceanothus herbaceus in Clintonville Pine Barrens 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 Balsam fir in boreal forest on Crane Mountain Cones point upward Red spruce in boreal forest Nun-Da-Gao Ridge Cones point downward Haystack Summit (4960’) – Very thin soil and cool conditions above treeline support alpine plant community Deer’s hair sedge on Haystack Summit Black crowberry (green) and mountain bilberry (red) on Noonmark in October Jay Range composed of gabbroic metanothosite In Summary: 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 Some books: •Rocks And Routes of the North Country – Bradford VanDiver •Geology of New York: A Simplified Account – University of the State of New York •Roadside Geology of New York - Bradford VanDiver •Bogs of the Northeast – Charles W Johnson A Map: •New York State Geologic Highway Map – University of the State of New York Lake Placid from Whiteface in winter [...]... western Adirondacks intruded during breakup of Grenville supercontinent 500 Million Years Ago: A Warm Shallow Sea 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 Beginning 60 to 15 Million Years Ago: Adirondack Mountains Form Great Range from Noonmark – Adirondacks. .. western Adirondacks From Pre-Grenville Ocean prior to Grenville Orogeny 1.1 Billion Years Ago: 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. .. reasons Some have attributed uplift to a hot spot, but there is not much evidence for that Beginning 1.6 Million Years Ago: Continental and Alpine Glaciation Glacial erratic near Debar Mountain in northern Adirondacks Potsdam Sandstone left by ice sheet on Poke-O-Moonshine Au Sable Chasm with Potsdam Sandstone Au Sable River has cut into the sandstone as uplift occurs Heart Lake from Mount Jo Some consider... Mountain with fall color at lower elevations, shows climate variation with elevation Mountain-ash on Saint Regis Mountain, October 8, 2000 Vegetation reflects geology 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 Pickerelweed