old rocks and new mountains: natural history of the adirondacks glenn a. richard
Post on 16-Dec-2015
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Relief Map of Adirondacks
The Adirondacks are a dome of old rock (1.1 billion years), surrounded by much younger rock (less than 600 million years)
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.
Roads
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’.
Cross section of Earth
Layers of the Earth:
•Inner Core
•Outer Core
•Mantle
•Crust
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).
Crust and very upper mantle are hard rock, called lithosphere.
Diagram by Keelin Murphy
Plate Boundaries
Divergent: East Pacific Rise
Convergent: West Coast of South America -Andes forming here
Transform: San Andreas Fault
Diagram by Keelin Murphy
Fossil stromatolite (blue-green alga, 1.3 bya) near Balmat in western Adirondacks. From Pre-Grenville Ocean prior to Grenville Orogeny .
1.3 Billion Years Ago: Pre-Grenville Ocean
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.
1.1 Billion Years Ago: Grenville Orogeny
Lake Placid from Whiteface. Shape is controlled by a group of faults that formed about 650 million years ago, when Grenville Supercontinent split up.
650 Million Years Ago: Grenville Supercontinent Breaks Up
Lake Placid from Whiteface. Shape is controlled by some of the faults that formed about 650 million years ago.
Faulting helps to create valleys and basins for
streams and lakes.
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.
500 Million Years Ago: A Warm Shallow Sea
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.
Beginning 60 to 15 Million Years Ago: Adirondack Mountains Form
Glacial erratic near Debar Mountain in northern Adirondacks
Beginning 1.6 Million Years Ago: Continental and Alpine Glaciation
Snow on Saint Regis Mountain with fall color at lower elevations, shows climate variation with elevation.
Maidenhair spleenwort - Asplenium trichomanes fern near Lake Champlain shoreline favors habitats where calcite is present.** Calcite is uncommon in Adirondacks **
Cotton grass on floating bog mat at Sunday Pond. Peat is acidic and water is low in oxygen and dissolved nutrients
Altona Flat Rock with Potsdam Sandstone – Pine barrens on very thin soil. Soil washed away by catastrophic flood during glacial times.
Haystack Summit (4960’) – Very thin soil and cool conditions above treeline support alpine plant community.
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
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