The place of interest
Grand Central Terminal is a commuter rail terminal located at 42nd Street and Park Avenue in Midtown Manhattan, New York City.
The distinctive architecture and interior design of Grand Central Terminal's station house have earned it several landmark designations, including as a National Historic Landmark. Its Beaux-Arts design incorporates numerous works of art. Grand Central Terminal is one of the world's ten most visited tourist attractions. The terminal's Main Concourse is often used as a meeting place, and is especially featured in films and television. Grand Central Terminal contains a variety of stores and food vendors, including upscale restaurants and bars, two food halls, and a grocery marketplace.
Grand Central Terminal was built by and named for the New York Central Railroad; it also served the New York, New Haven and Hartford Railroad and, later, successors to the New York Central. Opened in 1913, the terminal was built on the site of two similarly-named predecessor stations, the first of which dates to 1871.
In their design for the station's interior, Reed & Stem created a circulation system that allowed passengers alighting from trains to enter the Main Concourse, then leave through various passages that branch from it.Among these are the north–south 42nd Street Passage and Shuttle Passage, which run south to 42nd Street; and three east–west passageways — the Grand Central Market, the Graybar Passage, and the Lexington Passage — that run about 240 feet (73 m) east to Lexington Avenue by 43rd Street. Several passages run north of the terminal, including the north–south 45th Street Passage, which leads to 45th Street and Madison Avenue, and the network of tunnels in Grand Central North, which lead to exits at every street from 45th to 48th Street.
Each of the east–west passageways runs through a different building. The northernmost is the Graybar Passage, built on the first floor of the Graybar Building in 1926. Its walls and seven large transverse arches are made of coursed ashlar travertine, and the floor is terrazzo. The ceiling is composed of seven groin vaults, each of which has an ornamental bronze chandelier. The first two vaults, as viewed from leaving Grand Central, are painted with cumulus clouds, while the third contains a 1927 mural by Edward Trumbull depicting American transportation.
Any geology ? The Stylolites
► Définition
In Graybar Passage, the walls are covered with limestone's stones. These stones present stigmatas called stylolites, which are the marks of the rock turbulent past.
The name stylolite comes from the Greek words stylos (pillar) and lithos (stone). A stylolite is a geological structure formed during the compressive deformation of a rock. It consists of a crenellated surface where the rock has dissolved under significant compressive forces. The stylolite is in the form of a sawtooth line in a transverse sectional plane.
► Mechanisms of formation
Stylolites are mainly formed in carbonate sedimentary rocks, and in particular limestone. When sufficient compression is applied to a rock block, it tends to deform. Its dimension decreases in the direction of the maximum stress, and extends in the perpendicular direction corresponding to the smallest stress.
An area of the stone then has dissolution of silicate and carbonate particles. A seal is formed from the residues of the solution (mainly clays, sulphides, organic matter), and appears darker than rock. This dissolution responds to the maximum stress applied, by making it possible to reduce the size of the rock in the direction of this stress. The stylolithic surface then extends along a plane perpendicular to the maximum stress applied to the rock.
The irregular shape of the stylolite would be due to the presence of some minerals (pyrite, quartz) which would deflect the peaks.
The fluids containing the solubilized elements migrate and fill in tension slots, which are formed perpendicular to the stylolite seal. These tension slots open in the direction of minimum stress, and allow the rock to extend in that direction.
► Geometric classification
The geometry of the stylolites can be varied depending on the formation conditions. A classification was established by Park and Schot (1968) with 6 types :
To log this EarthCache, go to the coordinates located in the Graybar Passage via the entrance at 105 E 42nd St, locate the hidden stone on the picture, and answer the following questions.
1 ► Tell us with your words how is created a Stylolite
2 ► Observe the stylolite underneath the yellow masked area. What type are these stylolites?
3 ► Underneath the blue masked area. What type are these stylolites?
4 ► Where can you find others in Grand Station ?
5 ► Join to your log a photo (face not required) or a personal item on the site... but without showing elements that may compromise the resolution of the cache. Be creative but take care of restrictions ! (see https://www.grandcentralterminal.com/filming-photography/)
Bibliography :
- Grand Central Terminal - Wikipedia
- http://ficheinfoterre.brgm.fr
- https://fr.wikipedia.org/wiki/Stylolithe
- http://www.geoforum.fr/topic/23696-stylolithes/
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This earthcache is a tribute to the owners in NYC and the surrounding area,
in thanks for the pleasure we had during our too short stay in this city