Tag Archive for Succession

Arrested development

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Entrance to the Choate mine.

Entrance to the Choate chromite mine at Soldiers Delight in Maryland. Fall 1973.

Entrance to the Choate mine.

Entrance to the Choate mine. Although trash was being removed from the area, fresh appliances had been dumped above the entrance. Fall 1973.

Soldiers Delight would be a lot less interesting to some were it not for its contribution to the economic history of Baltimore County, Maryland. Serpentine outcrops including Soldiers Delight, Bare Hills, and the State Line Barrens in Pennsylvania supplied most of the world’s chromium ore in the mid 19th century. Issac Tyson, and later his sons, owned land and operated mines at these places, shipping all the chromite to Baltimore and monopolizing the industry from the 1820s until after the Civil War. But the long term impact of this activity may have been more ecological than economic.

Stemming the tide

Below is a diagram that was never shown to me in science class. Alfred Wegener proposed his theory of continental drift in 1912, but it was not until 1960 that most scientists began to accept the new paradigm that continents move around. The idea of crust formation at mid ocean ridges came even later in 1966. So when scientists and teachers in the 1950s and 1960s presented a story about the serpentine rock underlying Soldiers Delight, they got it wrong. Serpentinite is formed in the lower oceanic crust, typically at the mid ocean spreading centers. That’s where it picks up its heavy minerals, like chromium, nickel, and magnesium, which are more abundant in the mantle and deep crust. When Africa floated over here 300 million years ago, a little bit of this oceanic rock got pushed along with it and ended up in the Appalachian Mountains, and in Soldiers Delight. Nobody knew that in 1960.

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A diagram of magma rising through the mantle and forming new oceanic crust at a mid ocean rise. This is where serpentinite is formed.

A diagram of magma rising through the mantle and forming new oceanic crust at a mid ocean rise. This is where serpentinite is formed.

Copy that

Click photos to enlarge I watched eBay auctions for Nikon D3100 cameras for a day, then started watching auctions for D5100 cameras. I assumed that the upgrade from the Nikon D40’s six megapixels had to be at least to 14…

The succession of precedence

Google has digitized the text of five million books. The old ones are in the public domain and you can read them online at http://books.google.com/. Most of the more recent ones are still protected by copyright law, but that law…