The Staten Island Serpentinite locality is a southward extension of the
New England Uplands The topography of the New England Uplands section is that of a maturely-dissected plateau with narrow valleys, and the entire area is greatly modified by glaciation. It is the most widespread of the geomorphic sections in the New England Province, e ...
, adjacent to the
Manhattan Prong. It includes
Todt Hill
Todt Hill ( ) is a hill formed of serpentine rock on Staten Island, New York. It is the highest natural point in the five boroughs of New York City and the highest elevation on the entire Atlantic coastal plain from Florida to Cape Cod. The summi ...
on
Staten Island, which is the highest point along the Atlantic Seaboard south of Maine, at above sea level. "Todt" is a Dutch word meaning "dead." This hill perhaps received its name from the Dutch settlers because the hilltops overlooking
The Narrows
__NOTOC__
The Narrows is the tidal strait separating the boroughs of Staten Island and Brooklyn in New York City, United States. It connects the Upper New York Bay and Lower New York Bay and forms the principal channel by which the Hudson Riv ...
consisted of scattered treeless rocky exposures. The chemical character of the bedrock was, in part, the reason for this. Much of Staten Island is covered by the
Harbor Hill moraine, the terminal moraine of the last Wisconsin Stage glacier. However, ledges of bedrock consisting of
serpentinite
Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called ''serpentine'' or ''se ...
are exposed throughout the upland areas on Staten Island.
Grymes Hill, the second highest point on Staten Island and just a few miles from Todt Hill has similar bedrock characteristics. Serpentine, the dominant mineral in serpentinite, is rich in
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
, an element that most plants cannot tolerate in high concentrations. The enrichment of magnesium in the thin
serpentine soil covering the glacier-scoured hilltops is probably responsible for the original barren exposures on Todt Hill.
The serpentinite has a bluish to greenish gray color, and consists of serpentine (mostly the variety
antigorite), with accessory minerals of
chrysotile
Chrysotile or white asbestos is the most commonly encountered form of asbestos, accounting for approximately 95% of the asbestos in the United StatesOccupational Safety and Health Administration, U.S. Department of Labor (2007)29 C.F.R.&nb ...
(a form of asbestos), magnetite, and talc. Serpentinite is derived by the metamorphism of ultramafic rocks (rocks rich in the minerals olivine and pyroxene) in a water-rich environment. The probable original setting for these rocks was within the igneous crust beneath the
Iapetus Ocean. The occurrence of serpentinite in the core of Staten Island is an indication that the allochthonous basement rocks consisting of oceanic crustal material were thrust landward onto the eastern margin of the continent during the
Taconic orogeny. The occurrence of serpentinite is consistent with the interpretation that Staten Island is east of
Cameron's Line.
{{coord missing, New York City
Geology of New York (state)
Appalachian Mountains
Landforms of Staten Island
Serpentine group