Thursday, August 16, 2012


Drive north on I-87 from Albany toward Canada and you pass through a long stretch of the eastern Adirondacks.  Toward the north end of the park, between exits 32 and 33 (south of Keeseville), watch for the long, glacially-polished cliff of Poke-O-Moonshine Mountain on the left (west) side.  It's nearly a thousand feet high and a favorite of rock climbers.  You can get closer views by taking exit 33 and driving south on Route 9.  The mountain's name is derived from the Algonquin words for broken and smooth.

The north-south cliff is an up-thrown block of granitic gneiss along a fault line [a huge crack where there is enough pressure to shift the rocks out of alignment], while Route 9 traverses a down-dropped block of gneiss interfingered with anorthosite (very similar to Moon rocks) east of the cliff.  The term "block" may be misleading as these are large-scale structures with horizontal dimensions measured in miles. North-northeast of the mountain and continuing over halfway to Keeseville, Route 9 crosses the west edge of anorthosite mixed with metasedimentary rock (the green area on the geology map).

From the Geologic Map of New York - Adirondack Sheet
yellow is an extension of the Marcy massif, lavendar-pink is gneiss,
and green is a hybrid anorthosite mixed with metasedimentaries

Weathering of the cliff [a fault scarp, or escarpment] has obscured thick bands of darker rock, loosely classified as "metagabbro" (without knowing its original nature, either gabbro or basalt/diabase).  Although somewhat horizontal, the major rock layers have a gradual rise to the north (right).  In several locations, the bands are offset by vertical faults.  Also difficult to discern are thinner bands of dark diabase or basalt that intruded as molten sills between the bedded layers.

Like the core of the Adirondacks (actually a southeastward extension of the ancient Canadian Shield), the original sedimentary rocks of Poke-O-Moonshine were metamorphosed [transformed by intense heat and pressure just short of complete melting] during the Precambrian Grenville collision of pre-North America and pre-Europe/Africa around 1.1 billion years ago.  The name is taken from Grenville, Quebec.  The scarp's granitic gneiss is a strongly-banded and coarse-grained rock similar in composition to granite with feldspar, quartz and the dark minerals pyroxene, hornblende and biotite mica. The darker bands of "metagabbro" [a.k.a. amphibolite, a dark rock composed of hornblende and plagioclase with smaller amounts of biotite mica and/or dark-green pyroxene] were also metmorphosed by the end of the Grenville Orogeny [mountain-building episode] that completed the assembly of the supercontinent Rodinia at that time.  The thinner diabase sills were injected as hot, molten magma at a later date, likely after one of at least four collisions of North America and Europe when the continents were again separating and stretching the tectonic plates (which causes vertical cracks that allow magma to rise and then spread horizontally between bedded rock layers). Just south of the Adirondacks, in the Mohawk Valley, the diabase dikes [that cross-cut the older Precambrian rock layers] and the sills [that flowed between the layers] are also found in Cambrian and Ordivician rocks, but not the younger Devonian or Silurian deposits, so it's implied that they rose after the Taconic Orogeny when the continents began separating at the end of the Ordovician Period.

The anorthosite is related to the Marcy massif, a huge pool of crystalline rock under the High Peaks that entered (intruded) the surrounding Grenville rocks as a molten plume through cracks, spread laterally and then slowly cooled.  It can be likened to a geological breast implant.  Uplift and erosion has stripped more-recent rocks off the dome to expose the anorthosite.  A deeper hot spot is theorized to be fueling the continued rise in the Adirondack dome at the rate of three millimeters per year.  You may have heard the expression "new mountains from old rock."

The mineral composition of anorthosite rock is 90% plagioclase feldspar which forms under extreme heat and pressure at great depth (likely 15 miles, give or take a few) and can be termed Plutonic rock.  Plagioclase is a group of silicate minerals built around one silicon atom bonded with four oxygen atoms or three silicons plus eight oxygens.  These molecules combine with various amounts of sodium and/or calcium or potassium plus aluminum to form one of the minerals in the feldspar series.

Glacially-polished cliff face catches the morning sun, August 10, 2007.

The Grenville Province is a long band of rock stretching from the southern Appalachians north-northeastward through southern Ontario Province to the Laurentian Highlands of Quebec.  It's now moslty basement rock with narrow exposures in places like the Blue Ridge (NC/VA), South Mtn. (PA), the Hudson Highlands (NY), the Berkshires (MA), and the Green Mtns. (VT).  Also exposed are the Adirondack dome and the Frontenac Arc (across the Thousand Islands in the upper St. Lawrence River) which connects the Adirondacks to Ontario. The Grenville rocks were originally sediments, volcanics and plutonic (deep) intrusions that were metamorphosed (i.e., transformed or recycled by heat and pressure at great depth) during the Grenville Orogeny between 1.2 and 1.0 billion years ago in a process that resets the rock's "geological clock."  The Grenville collision completed the assembly of the Rodinia supercontinent.

Corrections, comments and questions are always welcome at or connect through my Facebook page or my photo page.  Other outdoor topics can be found on the parallel blog


2 books by Bradford VanDiver, PhD: Rocks and Routes of the North Country (1976) and Roadside Geology of New York (1985/2003)

Geology of New York, NYS Museum (1966/1976)

Geology of the Adirondack High Peaks Region, Howard & Elizabeth Jaffe, 1986, is not directly relevant to Poke-O-Moonshine, but has a good overview with diagrams in the "Introduction and Geologic History."  Their dates for Grenville events are slightly older.

[also several general rock and mineral guides]

Saturday, August 11, 2012

Narrowleaf? Gentian

Narrow-leaved Gentian on Whiteface - © Dave Spier
Gentian on Whiteface -- © Dave Spier

For some reason, gentians have always fascinated me.  Maybe it's because I usually come across one of the closed or bottle-type gentians and wonder how it gets pollinated.  Such is the case with a tentatively-identified Narrow-leaved Gentian (Gentiana linearis), a.k.a. Narrowleaf Gentian, beside the Memorial Highway on Whiteface (Mountain) above Wilmington.  It has showy violet-blue flowers, but the tips of the five lobes ("petals") bend in at the top and meet. [ I found one source claiming it has four petals, but it's my personal policy to not disturb native wild flowers and I didn't think to count the lobes at the time. Fringed gentians have four obvious petals, so that's likely where the confusion lies.] Soapwort Gentian (Gentiana saponaria), generally a more southerly species,* is another possible ID, but its flowers tend to be slightly open at the top and fringed between the lobes.
I imagine insects force their way in to reach the gentian's nectary glands. Apparently this perennial is of special benefit to bumble bees, and I assume they're the ones strong enough to part the tips.  Sorry, I didn't stay around long enough to find out.

On G. linearis, the lance-shaped leaves are opposite on a single stalk, and the sepals (modified leaves) at the base of the flowers are a similar shape. By comparison, the leaves of Soapwort Gentian are slightly wider with a broader point at the tip.

Narrow-leaved Gentian is found from Manitoba to Maine and south in the mountains to Tennessee. The USDA Plants Database map for New York shows its range spread around the Adirondacks plus one county in the Catskills, indicating it's a higher-elevation species. *Several similar species of the blue closed/bottle gentians have more southerly ranges. Red species of gentians are dominant in the Andes where they are more dependent on pollination by birds.

Corrections, comments and questions are always welcome at or connect through my Facebook page or my photo page.  Other nature topics can be found on the parallel blog

Newcomb's Wildflower Guide, by Lawrence Newcomb and Gordon Morrison (© 1977), published by Little, Brown & Co. -- see page 252
USDA Plants Database at
Ladybird Johnson Wildflower Center at

Friday, August 10, 2012


First off, they're not weeds.  They're attractive native wildflowers.  Second, and this is unfortunate, they are not jewels.  The name comes from water's inability to wet the leaves, so after a rain or morning dew, beads of water rest on the surface and scatter light like diamonds.  The plant's alternate name, touch-me-not, refers to the small seed pods that spring open and eject its seeds if you touch them when plump and ripe.

There are two species based on color. The orange species, a.k.a. Spotted Touch-me-not (Impatiens capensis) is speckled with reddish-brown and its long tail spur curls underneath the back end of the irregular blossom. It prefers wet ground and I've found it in places like the soggy edges of Middle Pond near Saranac Inn.  Ruby-throated Hummingbirds love this plant.

The dangling, one-inch flowers [roughly the length and width] of the yellow version, also called Pale Touch-me-not (Impatiens pallida) have a tail-spur that points down.  It's mostly found in limestone regions with alkaline soils and prefers damp locations like wooded flood plains and shady ravines with a steady supply of moisture.  I'd look for it in the marble (metamorphosed limestone) belts of St. Lawrence County and the limestone bands on the edge of the Adirondacks.

Impatiens are succulents with translucent green stems.  The crushed leaves and stem juice (particularly from the Orange Jewelweed) are folk remedies for poison ivy rash, insect bites, nettles, minor burns and cuts.

Young shoots in spring and the stems and leaves in summer can be eaten as cooked greens.  Boil in two changes of water and discard the water.

Corrections, comments and questions are always welcome at or connect through my Facebook page or my Facebook photo page

Friday, August 3, 2012


Cardinal-flower beside the Moose River in the Nelson Lake vicinity, August, 2010
Cardinal-flower -- © Dave Spier

This native perennial grows wild along streambanks and in swamps and other wet places up and down the eastern half of the U.S., northeast into Canada and south to Columbia. I've found it in places like Copper Rock Falls on the Grass River (St. Lawrence County) and beside the Moose River (Herkimer County). The plant can reach two or three feet in height, making it a nice addition to any garden if you want it closer to home.

The Cardinal-flower (Lobelia cardinalis) gets its name from the bright-red blossoms hugging the upper stem. (Although sometimes called a spike, it is technically a raceme because of short flower stalks called pedicels.) Look closely at an individual corolla [flower] and you’ll notice three wide lobes forming a lower lip while two narrow lobes extend to the sides like arms. The male and female parts, also scarlet colored, form a narrow projection emerging like a crane above the petals. The base of the flower is a tube that seems perfectly made for hummingbird beaks.

Leaves are lance-shaped, long-pointed and serrated or toothed on the edges and they alternate on a single, main stalk.

Cardinal-flower contains alkaloids and should be considered toxic, as are other members of the genus Lobelia. In spite of this, Native Americans used root and leaf teas for various ailments.

Cardinal-flower and its relative, the blue-violet Great Lobelia (another moist-ground species) belong to the Lobelia subfamily of the Bluebell family.

Corrections, comments and questions are always welcome at Now you can connect through my Facebook photo page at Dave Spier (photographic naturalist) or my personal page, Dave Spier, northeast naturalist.