Willamette Meteorite at the American Museum of Natural History
|Structural classification||Medium Octahedrite|
|Composition||7.62% Ni, 18.6ppm Ga, 37.3ppm Ge, 4.7ppm Ir|
|TKW||14,150 kilograms (15.60 short tons)|
The Willamette Meteorite, officially named Willamette, is an iron-nickel meteorite discovered in the U.S. state of Oregon. It is the largest meteorite found in North America and the sixth largest in the world. There was no impact crater at the discovery site; researchers believe the meteorite landed in what is now Canada or Montana, and was transported as a glacial erratic to the Willamette Valley during the Missoula Floods at the end of the last Ice Age (~13,000 years ago). It was long held sacred by indigenous peoples of the Willamette Valley, including the federally recognized Confederated Tribes of the Grand Ronde Community of Oregon (CTGRC). The indigenous peoples referred to this stone with the name Tomonowos (the visitor from the sky).
The meteorite is currently on display at the American Museum of Natural History in New York, which acquired it in 1906. Having been seen by an estimated 40 million people over the years, and given its striking appearance, it is among the most famous meteorites known. In 2005, the Confederated Tribes of the Grand Ronde Community of Oregon sued to have the meteorite returned to their control but they were unsuccessful.
Physical characteristics and formation
The Willamette Meteorite weighs about 32,000 pounds (15,000 kg). It is classified as a type III iron meteorite, being composed of over 91% iron and 7.62% nickel, with traces of cobalt and phosphorus. The approximate dimensions of the meteorite are 10 feet (3 m) tall by 6.5 feet (2 m) wide by 4.25 feet (1.3 m) deep. Most iron meteorites like Willamette have originated from the differentiated core of planetesimals or asteroids that collided with another object. Willamette has a recrystallized structure with only traces of a medium Widmanstätten pattern; it is the result of a significant impact-heating event on the parent body. The Willamette Meteorite contains higher concentrations of various metals that are quite rare in Earth's crust. For example, Iridium, one of the least abundant elements in Earth's crust, is found in the Willamette Meteorite at a concentration of 4.7 ppm, thousands of times more than its crustal abundance.
Emplacement and erosion
The lack of an impact crater at the discovery site was only explained after the 1920's, with the new understanding about the Missoula Floods, one of the largest floods documented, caused by the collapse of an ice barrier during the last deglaciation. The meteorite presumably landed on an ice cap in what is now Montana or western Canada, and was transported as a glacial erratic (dragged by the glacier ice) to the vicinity of an ice barrier that formed across the Clark Fork River. This barrier had ponded a huge amount of water at the Lake Missoula right at the time when the meteorite reached the area and the ice barrier became unstable and breached. The resulting flood involved up to 10 million cubic meters per second of water discharge, with large blocks of ice rafting down the Columbia River and the Willamette Valley at the end of the last Ice Age (~13,000 years ago). Some of these ice rafts included boulders (named erratics by geologist) like the Willamette meteorite, which eventually sunk in the flood waters and settled where it was found by humans.
The deep crevasses of the meteorite resulted from both its high-speed atmospheric entry and subsequent terrestrialization, i.e., weathering. Exposed to the elements for thousands of years, rainwater interacted with the mineral troilite, resulting in a form of sulfuric acid which slowly dissolved portions of the meteorite. This resulted (over a very long period) in the development of the hollows that are visible today.
The Willamette Meteorite was discovered in the Willamette Valley of Oregon near the modern city of West Linn. Although already known and sacred to Native Americans, its "discovery" was made by settler Ellis Hughes in 1902. At that time the land was owned by the Oregon Iron and Steel Company. Hughes recognized the meteorite's significance, and in an attempt to claim ownership, secretly moved it to his own land. This involved 90 days of hard work to cover the 3/4 mile (1200 m) distance. The move was discovered, and after a lawsuit, the Oregon Supreme Court held that Oregon Iron and Steel Company was the legal owner. Oregon Iron Co. v. Hughes, 47 Or 313, 82 P 572 (1905).
In 1905 the meteorite was purchased by Mrs. William E. Dodge for $26,000 (around $680,000 in 2011). After being displayed at the Lewis and Clark Centennial Exposition, it was donated to the American Museum of Natural History in New York City where it has since been on display.
The meteorite was venerated by the Clackamas tribe inhabiting the area where it was found. The Confederated Tribes of the Grand Ronde Community of Oregon, a confederation of Native American tribes, used the meteorite, which they call Tomanowos, in ceremonies and demanded that it be returned and filed a NAGPRA action (Native American Graves Protection and Repatriation Act) against the American Museum of Natural History in 1999. In response, the Museum filed a federal lawsuit seeking a declaratory judgment against the Grand Ronde in 2000. An agreement with the Museum was reached later that year in which the meteorite would remain at the museum with tribal members being able to conduct a private ceremony around the meteorite once a year, and that ownership will be transferred to Grand Ronde should the museum cease to have the meteorite on display.
In response to a student's request in 2007, Representative John Lim introduced a resolution that would demand that the museum return the meteorite to Oregon. The tribes said they were not consulted, they did not support the resolution, and were content with the current arrangement with the museum.
The 28-pound (13 kg) crown section of the meteorite that had been traded to the Macovich Collection for a Martian meteorite in 1997, was planned to be auctioned in October 2007, which led to claims by the Grand Ronde of insensitivity. Bidders dropped out when an editorial in the Portland Oregonian newspaper asserted the Grand Ronde would file a lawsuit against the new owner, but the Grand Ronde disavowed the editorial and said they had no such intent, and that they couldn't stop the sale. While the newspaper printed an apology, the specimen was withdrawn. A lawsuit was filed against the newspaper in Oregon Circuit Court and failed.
A 4.5-ounce (130 g), 7.5-inch (19 cm) piece of the meteorite, also with a Macovich Collection provenance, was purchased in a 2006 auction and is on display at the Evergreen Aviation & Space Museum in McMinnville, Oregon.
There is some confusion about the actual mass of the Willamette meteorite due difference between metric tons and short tons, often both referred simply as tons. The result is that several sources report different weights ranging from 15,500 kilograms (34,200 lb) to 12,700 kilograms (28,000 lb). The official American Museum of Natural History website also reports both "15.5 tons" and "14 tons". However 15,500 kg is likely 15.5 short tons converted as metric tons and 12,700 kg is likely 14 metric tons converted as short tons. Moreover in 1906 the American Museum of Natural History itself stated that the weight of the Willamette meteorite was at least 31,200 pounds, or about 15.6 tons. After these considerations it is reasonable to guess that the real weight of the meteorite is about 14,150 kilograms (31,200 lb).[original research?]
A replica of the meteorite is in Eugene, Oregon, outside the University of Oregon Museum of Natural and Cultural History on the University of Oregon campus. Another replica stands near the Willamette Methodist Church in West Linn, Oregon.
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- Meteoritical Bulletin Database: Willamette
- Harry Y. McSween. Meteorites and Their Parent Planets. Cambridge University Press, 1999.
- Planets Zone, Rose Center for Earth and Space. American Museum of Natural History. Retrieved on August 16, 2008.
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|Wikimedia Commons has media related to Willamette meteorite.|
- On the agreement between American Museum of Natural History and the Confederated Tribes of the Grand Ronde Community
- Map reference
- Articles search result for "Meteorite" on the Confederated Tribes of the Grand Ronde website
- Geological Society of Oregon on the Missoula Floods & the Willamette Meteorite
- About the Williamette [sic] Meteorite in Oregon