2016-10-04

Tomanowos - the rock that went through cosmic billiard, megafloods, and idiocy

Present display of the meteorite at the at the at the AMNH. My photo.
Last week I faced the rock with the most fascinating story on Earth: 
Tomanowos, meaning the visitor from the sky in the extinct Clackamas language, also known as the Willamette meteorite. 
Supernovas spread throughout space the
iron produced in heavy stars. This ejected iron
ends up in particle nebulas that eventually form
new stars and protoplanets. [Image: NASA] 

After being seen by european americans near Portland, more than a hundred years ago, Tomanowos inevitably went through one of the most hilarious and silly geological stories that I know of, surely driven by the fatal attraction that a weird rock like this irradiates on humans. But before going to that: what do we know about this weirdness?

Tomanowos is a rare 15,500-kg meteorite made of iron and nickel (Fe 91%, Ni 7.6%). As in other metal meteorites, these Fe and Ni atoms formed at the core of stars that shattered the space with the sub-products of nuclear fusion when ending their lives as supernovae. Such space bodies eventually formed the nebula that clumped together as protoplanets in the Solar System, and Tomanowos was part of the core of one of these protoplanets, where the heavier metals accumulate. 


Vesta, a surviving protoplanet of the 
early Solar System. Due to their large
 size, protoplanets develop a differenciated 
density distribution with heavier elements like 
iron concentrated in the core. Tomanowos is an 
ejected piece of a protoplanet core like this. 
[EPFL/Jamani Caillet, Harold Clenet]
Then, a collision 4 billion years ago between two of those protoplanets sent our museum piece back to space solitude. Subsequent impacts over billions of years made the orbit of the meteorite eventually go across that of the Earth. As a result of this cosmic billiard, about 20,000 years ago, the meteorite entered our atmosphere at a speed of ~60,000 km per hour and landed on an ice cap in Canada.

Over the following decades, the ice flow slowly brought Tomanowos southwards, towards a glacier lobe that was at the time blocking the Fork River in Montana. The glacial tongue piled ice across the river valley forming a 600-m barrier that impounded the enormous Lake Missoula behind. Tomanowos happened to reach the ice dam on the precise year when it collapsed, releasing one of the largest floods ever documented: the #MissoulaFloods that shaped the Scablands in Washington. This process is known as glacial outburst flooding and it still happens every few years in the Perito Moreno glaciar, for example. Except that the water discharge during the Missoula Floods reached the equivalent to a few thousand Niagara Falls. The research of the Missoula floods by Bretz and Pardee in the early 20th century led to one of the most significant paradigm shifts in recent geoscience: the recognition that catastrophic events can significantly contribute to landscape evolution.
Map of the Missoula Floods path, showing Lake Missoula 
(blue), the ice cap where Tomanowos landed (north of the 
lake outlet), and the inundated areas of Washington and 
Oregon (grey).
Source: Washington Univ.

Trapped in ice and rafted down by the flood, Tomanowos crossed Idaho, Washington and Oregon along the overflown Columbia River at speeds sometimes faster than 20 meters per second. While floating up on the flood waters near today's Portland, the ice case broke apart and the meteorite sunk in the flooding waters. Hundreds of other ice-rafted erratics (rocks that do not match the local geology, nor could be transported by rivers or glaciers) have been found along the Columbia River. All are souvenirs from the Missoula floods.

As the flood ceased, the sunk meteorite became exposed to the atmosphere. Over thousands of years, rain mixed with the iron sulfide inclusions producing sulfuric acid that gradually dissolved the iron of the exposed side of the rock:
These cavities were produced by acid dissolution of iron at the exposed side.
A few thousand years after the flood, the Clackamas arrived to Oregon and named the meteorite as the Visitor of the Sky, a heaven's representative that unified earth, water & sky. Did they know that nickel rocks come from heaven? Were they intrigued by the absence of a crater at the Meteorite site? In any case, the name reminds us that pre-scientific cultures were not idiotic, or not more than us today anyway.

To confirm this latter hypothesis, in 1902 a colonist named Ellis Hughes decided to literally move the iron rock to his own land and claim property. Millennia of peaceful rest in the Willamette had to come to an end. But since moving a 15-ton rock a distance of 1,200 m without being noticed is not easy, not even in Oregon, Hughes and his son labored for three back-breaking months in secrecy: 

As D. J. Preston hilariously explains, after finally
succeeding with the moving, Hughes built a shack around
the meteorite, announced he had found it on his property
and started charging twenty-five cents admission to view
the heavenly visitor.
It was during this transport that the rock sadly underwent severe mutilations.
Unimpressed by this deployment of idiocy, Hughes' neighbor fabricated a lawsuit contending that the meteorite had, in fact, landed on HIS property. And to buttress his case he showed investigators a huge crater on his land. The case was dismissed when a third neighbor reported a great deal of blasting only the week before.

Ironically, the legitimate owner of the original land of the iron meteorite turned out to be the Oregon Iron and Steel Company, which was unaware of the meteorite but soon hired a twenty-four-hour guard who sat on top with a loaded gun while the case was being appealed. They won in 1905 and sold Tomanowos to the AMNH museum in New York, a year later.
Tomanowos in the early 1900s, before being transported to the AMNH.

Today, amazingly enough, the @AMNH exhibition does not even mention the Missoula Floods as a key part of Tomanowos' story, in spite of the wide scientific consensus. But the descendants of the Clackamas still keep the right to visit the meteorite and talk to the visitor who brought the Sky, the Water, and the Earth together.