Page 19 - visitorGuide

Outdoor Exhibits

■ Society Plaque
Arriving at GSA, you will notice that our building is situated on two scenic
acres, with an additional two acres surrounding the building, populated by a
variety of indigenous trees. Next to the sidewalk to the right of the front park­
ing lot (facing west) is the original bronze plaque, now set in moss rock, that
welcomed visitors to the Society’s first headquarters building in New York
more than a hundred years ago.
The stone and its emplacement are a gift from Luna B. Leopold, University of California at Berkeley, and a former president
of the Society.

■ Doris Malkin Curtis Memorial Plaque and Colorado Blue Spruce
Doris Curtis (1914–1991), first woman president of the Geological Society of
America, was widely admired for her spirit, her energy, and her contributions
to science and to the geoscience community. During her career in the petro­
leum industry, academia, and consulting, she held leadership roles in a num­
ber of prominent geological and scientific organizations.
The plaque and the Colorado blue spruce were donated by GSA staff.

■ Stromatolite
Located in the rockbed to the right of the front parking lot, adjacent to the walk­
way, this two-ton specimen is from the 1.8-billion-year-old Kona Dolomite in
the Chocolay Group of the Marquette Range Supergroup near Negaunee,
Michigan.

The laminated domes in this ancient rock are stromatolites.They were built
layer by layer almost 2 billion years ago by colonies of blue-green algae liv­
ing at the bottom of a shallow sea. As part of their life processes, the algae
secreted calcium carbonate, the same mineral that forms limestone. The cal­
cium carbonate settled in thin layers that the algae grew over and through.
Tiny grains of sediment were trapped in the layers, too. When the sediments
were later converted to rock, they formed an impure limestone. Later still,
they metamorphosed into dolomitic marble that still displays the stromato­
lites that the algae built.
Located by David K. Larue. Gift from A. Lindberg and Sons, Inc., of Ishpeming, Michigan, through L.L. Sloss.

■ Sundial
Carved in a polished slab of serpentine, the sundial to the left of the front
walkway is a small but significant marker leading to the building.The sundial
shows the exact time only four days each year: 15 April, 14 June, 1 September,
and 25 December. During the summer, it is incorrect by as much as 6.5 min­
utes (on 26 July); in winter, it is off by as much as 16.4 minutes (on 3 Novem­
ber). In addition to these errors, which are related to Earth’s orbit, the time
shown is a full hour off during daylight-saving periods.
The origin of the stone is uncertain, but it was probably collected for the Smithsonian Institution by George Merrill. The stone
itself was a gift from the U.S. National Museum of Natural History, Smithsonian Institution, Washington, D.C., through George
Switzer and Harold H. Banks, Jr. Its transfiguration into a sundial is the gift of August Goldstein, Jr., Tulsa, Oklahoma, former
treasurer of the Society. Calculations, design, and cutting were by Milton Erickson, Erickson Memorial Co., Denver, Colorado.

OUTDOOR EXHIBITS 9