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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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Presentation Transcript
slide1

Adirondack Geology:

Old Rocks

and

New Mountains:

Glenn A. Richard

slide2

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

slide3

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.

slide4

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).

Roads

slide5

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).

slide6

Shore of Lake Champlain (elevation 95 feet) from eastern Adirondacks. Lowest elevation in Adirondacks.

slide7

Haystack from Marcy – July 2, 2001. Rugged topography caused by faulting, uplifting, erosion by water and glacial ice.

slide9

Picea rubens and Abies balsamea just below tree line on Haystack, third highest peak in the state at 4960’.

slide10

Cross section of Earth

  • Layers of the Earth:
  • Inner Core
  • Outer Core
  • Mantle
  • Crust

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).

slide11

Diagram by Keelin Murphy

Plate Boundaries

Transform: San Andreas Fault

Divergent: East Pacific Rise

Convergent: West Coast of South America -Andes forming here

slide12

1.3 Billion Years Ago: Pre-Grenville Ocean

Fossil stromatolite (blue-green alga, 1.3 bya) near Balmat in western Adirondacks. From Pre-Grenville Ocean prior to Grenville Orogeny .

slide13

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.

slide15

650 Million Years Ago: Grenville Supercontinent Breaks Up

Lake Placid from Whiteface. Shape is controlled by a group of faults that formed about 650 million years ago, when Grenville Supercontinent split up.

slide16

Colden, Avalanche Pass, Algonquin, Indian Pass, Wallface. Passes are valleys formed along faults.

faulting helps to create valleys and basins for streams and lakes
Faulting helps to create valleys and basins for streams and lakes.

Lake Placid from Whiteface. Shape is controlled by some of the faults that formed about 650 million years ago.

slide18

Diabase dike (650 mya) in western Adirondacks intruded during breakup of Grenville supercontinent.

slide19

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.

slide20

Beginning 60 to 15 Million Years Ago: Adirondack Mountains Form

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.

slide21

Beginning 1.6 Million Years Ago: Continental and Alpine Glaciation

Glacial erratic near Debar Mountain in northern Adirondacks

slide23

Au Sable Chasm with Potsdam Sandstone. Au Sable River has cut into the sandstone as uplift occurs.

slide25

Snow on Saint Regis Mountain with fall color at lower elevations, shows climate variation with elevation.

slide27

Vegetation reflects geology

Red oak at Lake Champlain shore. Soil in Adirondacks is mostly acid.

slide31

Cotton grass on floating bog mat at Sunday Pond. Peat is acidic and water is low in oxygen and dissolved nutrients

slide42

Altona Flat Rock with Potsdam Sandstone – Pine barrens on very thin soil. Soil washed away by catastrophic flood during glacial times.

slide49

Haystack Summit (4960’) – Very thin soil and cool conditions above treeline support alpine plant community.

slide53

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

slide54

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