The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on an occasional schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Tuesday, January 27, 2015

Episode 368: Alaska, 1898



Today’s episode is from my book, What Things Are Made Of and the chapter that includes gold.

THE LAST GREAT GOLD RUSH began in August 1896, when prospector George Washington Carmack and his two Indian companions, Skookum Jim and Tagish Charlie, found gold in the Klondike River basin in Canada’s Yukon Territory. Two years later, thousands of the gold seekers who had climbed the perilous slopes of Chilkoot Pass were gone, either back to the states or on to other diggings in Alaska. But that summer of 1898 saw a rush of another sort: the rush to understand Alaska’s resources.

The 19-year-old United States Geological Survey dispatched four parties that spring, and the War Department sent two more teams accompanied by geologists. Among other things, they were to “observe and note all occurrences of valuable minerals, giving special attention to the presence or absence of gold, whether in placers or veins.” These early scientific expeditions guided later exploitation of Alaska’s mineral wealth, and established the careers of several USGS geologists.

Spurr's 1898 geologic map of southwestern Alaska

Josiah Spurr was just 28 years old when he led a reconnaissance in southwestern Alaska, but he knew what he was looking for: his previous geological experience in the Yukon gold fields prepared him for any exploration dealing with gold. Spurr’s 1425-mile Alaskan journey with a handful of other scientists in three lightweight cedar canoes resulted in new geologic and topographic maps covering a vast territory. Spurr’s report reflects the dangers of exploration as the 19th Century came to a close. The team arrived at Tyonek on Cook Inlet, on April 26, 1898, but could not head upriver until the ice began to break up on May 4. After reaching the Susitna River mouth, their intended portal to the interior, the weather forced a delay until May 20 when the river became sufficiently ice-free for them to travel. Even then, after they “had gone several miles, we were surprised by a solid wall of ice bearing swiftly down upon us, and we had only time to throw our load upon the banks and drag the boats out of the water before the ice jam swept past, piling over upon the banks in places and grinding off trees.” Spurr’s narrative reads more like an adventure story than a scientific document.

The Spurr Expedition coined the term alaskite, a word for a particular light-colored granitic rock. The scientists observed considerable mineralization associated with southwestern Alaska’s granites, though gold occurred only sparingly. Nonetheless, in 2007 Alaska was the second-leading gold producing state in the U.S., with more than 700,000 ounces, mostly from mines near Fairbanks and Juneau. Alaska’s production is a distant second to Nevada, the heavyweight in the U.S. gold-mining industry with around 5,000,000 to 7,000,000 ounces per year. The United States exports gold, in a virtual three-way tie with Australia and South Africa for second, third and fourth place in the world after China.

Josiah Spurr’s work on western U.S. mineral deposits gained him considerable fame, and he wrote a book on economic geology. In the 1940s his work focused on the moon – earning him a crater named Spurr to go with Spurr Volcano in Alaska and the mineral spurrite, a complex calcium silicate. Another 1898 Alaska explorer, Walter Mendenhall, became the fifth Director of the U.S. Geological Survey in 1930 and gave his name to a glacier near Juneau. Alfred Hulse Brooks, chief Alaska geologist for the USGS from 1903 until he died in 1924, explored Alaska’s interior Tanana River valley in 1898 when he was just 27 years old, and was honored by the naming of the Brooks Range in 1925. The rare mineral hulsite, an iron-magnesium-tin borate, discovered at Brooks Mountain on the Seward Peninsula, also bears his name. George Eldridge and Robert Muldrow led an 1898 expedition that accurately pegged the height of Mt. McKinley, or Denali, at 20,464 feet – remarkably close to today’s value, 20,306 feet. Glaciers descending from Denali’s flanks recall their names. In this way, gold set the stage for Alaskan geological investigations that continue into the 21st Century, and pointed ultimately to the United States’ largest oil field, Prudhoe Bay, and the world’s largest known zinc deposit, at Red Dog, in the western Brooks Range of northern Alaska.
—Richard I. Gibson

Spurr's complete report: Spurr, J.E., 1900, A reconnaissance in southwestern Alaska, 1898, in Walcott, C.D., Twentieth annual report of the United States Geological Survey, 1898-1899: Part VII - explorations in Alaska in 1898: U.S. Geological Survey Annual Report 20-VII, p. 31-264.

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