On May 10, 2001, construction workers discover a mammoth tusk in a site being prepared for a new parking lot in the small town of Moxee, just east of Yakima. Fossil experts at the Quaternary Research Center at the University of Washington later conclude that the tusk came from an animal swept to its death about 14,500 years ago, by one of the cataclysmic floods that periodically inundated the Pacific Northwest during the last Ice Age.
The tusk, about four and a half feet long, was located in an area that was being graded to provide parking for a manufacturing and distribution center operated by Alexandria Moulding Inc. Contractor Steve Herke was operating an earthmover when he noticed the tusk. Company officials stopped work at the site and contacted archaeologists at Central Washington University, Yakima Valley Community College, and elsewhere. "We knew it was something special," Herke said. Unfortunately, steps were not taken to protect the tusk from the hot, dry air until experts from the Yakima Valley Museum began excavations, about five days after the discovery. The brief exposure caused some of the top layers to fracture. "This end of it was intact," Dan Close, general manager at Alexandria, told a reporter. "Now it's almost dried into a powder" (Yakima Herald-Republic, May 24, 2001).
The tusk was originally thought to have belonged to a mastodon. Subsequent tests showed that it came from a Columbian mammoth (Mammuthus columbi) -- the official Washington State Fossil -- a distant relative of the modern-day elephant. Adult mammoths measured about 12 to 14 feet high at the shoulder and weighed between eight to ten tons. The animals inhabited the Northwest for about 400,000 years until they became extinct about 10,000 years ago, possibly because of climate change or overhunting by humans or both.
An Ice Age Flood
Mammoths were grass-eating creatures who preferred open plains; mastodons, their smaller cousins, lived in valleys, lowlands, and swamps. The Moxee mammoth probably died somewhere far from Yakima and was rafted into the valley by one of the floods. Its tusk was found on the top of an ancient riverbed, beneath eight feet of soil, in an area that was backflooded by water trying to squeeze through Wallula Gap, 100 miles to the southeast. During a typical Ice Age flood, water poured into Wallula Gap faster than it could drain out. The overflow created a huge, temporary inland sea that stretched all the way into the Yakima Valley. Sand, silt, rocks, animal carcasses, and other debris settled out of the water as it slowly cleared the clog at Wallula Gap. The pattern was repeated several dozen times as glacial dams formed and collapsed during the last Ice Age.
Studies at the Moxee site continued for about a year. Excavators found a few bone chips but no other traces of a mammoth. The dig was closed and the wood products company took back its parking lot in August 2002.
Yakima Valley Museum curator Andy Granitto says perhaps the most significant discovery made at the site was the identification of at least six distinct layers of flood deposits above the tusk itself -- a measure of the power and reach of the Ice Age floods. Twelve other mammoth finds have been recorded in the Yakima Valley; most are associated with so-called slackwater areas, where the floodwaters temporarily slowed and ponded. The tusk’s final resting place is an exhibit in the museum.