On the shores of the Rivers of America in Disneyland USA is one of the park's most interesting, unsung attractions. Virtually every Disney fan who knows of the existence of the Petrified Tree knows the story of how it arrived in the Happiest Place on Earth: how Walt bought it for Lillian as a birthday present because it was filled with opal and how she donated it to the park. What is the story of this natural marvel before it got to Disneyland? How did it form and what do we know of the environment when it lived millions of years ago?
According to the plaque describing it:
THIS SECTION WEIGHS FIVE TONS AND MEASURES 7 1/2 FEET IN DIAMETER. THE ORIGINAL TREE, ESTIMATED TO HAVE BEEN 200 FEET TALL, WAS PART OF A SUB-TROPICAL FOREST 55 TO 70 MILLION YEARS AGO IN WHAT IS NOW COLORADO. SCIENTISTS BELIEVE IT TO BE OF THE REDWOOD OF SEQUOIA SPECIES. DURING SOME PREHISTORIC ERA A CATACLYSMIC UPHEAVAL CAUSED SILICA LADEN WATER TO OVERSPREAD THE LIVING FOREST. WOOD CELLS WERE CHANGED DURING THE COURSE OF TIME TO SANDSTONE. OPALS WERE FORMED WITHIN THE TREE TRUNK ITSELF.The tree originated from the Florissant Fossil Beds (called the Pike Petrified Forest at the time), which became a National Monument in 1969. When Walt bought the stump in 1956, the beds were privately owned and in reckless danger of being completely exploited by prospectors. A long legal battle ensued, the National Monument established, and today some 30 petrified stumps are protected for the enjoyment of over 60,000 visitors a year.
A witty photo of a petrified stump, Florissant Fossil Beds.
Photo: Jeff Kramer.
The age given by the plaque at Disneyland is off by a few million years. Radiometric dating of argon has placed the site at the late Eocene epoch, approximately 34 million years ago. During the Eocene, the Earth was warmer than it is now, but North America was assuming its modern shape. Through the Cretaceous period, 70 million years ago, an inland sea stretched across North America from the Arctic Circle down to the Gulf of Mexico. This was known as the Western Interior Seaway, and was home to such creatures as Mosasaurs (imagine a Komodo Dragon with flippers) and Ammonites (an extinct relative of the Chambered Nautilus). The shoreline was a warm, wet tropical swampland similar to the shores of Louisiana and the Carolinas, but suffering from the sort of storms and flooding we see today in places like Bangladesh. These torrential storms caused the immense dinosaur bone beds that are found in places like Dinosaur Provincial Park in Alberta, Canada. Towards the end of the Cretaceous, tectonic movement was bringing the North America Plate into collision with the Pacific Plate, raising the mountain ranges of the Cordillera. This tremendous force pushed the entire continent up, draining the Western Interior Seaway. By the Eocene, all that remained of this once vast inland sea was the Gulf of Mexico.
North America, 70 million years ago.
North America, 65 million years ago.
North America, 40 million years ago.
Paleomaps by Dr. Ron Blakey.
Warmer, wetter climate and nutrient rich sediments eroding from the rising mountains to the west created a fertile environment for the growth of redwood forests in Colorado. The Florissant site shows an ancient lake surrounded by great trees in excess of 200 feet in height. It was an idyllic environment comparable to the Pacific Northwest or Sierra Mountains today, buzzing with bees, dragonflies, butterflies and cicadas. On the ground were spiders, millipedes, snails, shorebirds, opossum, and the odd dog-sized, three-toed ancestor of the modern horse. The lake was stocked with clams, perch, bowfin and catfish. Overall, it would have been very comfortable and familiar for the time travelling tourist from today.
Modern redwood forest. Photo: NPS.
Like the Pacific Northwest, there was a dark shadow looming over such natural beauty: a volcanic field 12-18 miles southwest of the lake. The Thirtynine Mile Volcanic Field formed by the same tectonic forces that were creating the Cordillera and the Columbia Plateau, spewing lava, ash and mudflows across the region. The main volcano, called the Guffey Volcanic Center, was comparable to Mount St. Helens. Like the famous mountain, this volcano's explosion rained ash on the forest and lakes, creating algal blooms that choked out insect and fish life. Ironically, the low-oxygen environment and protective layer of algae in turn preserved these specimens as fossils. The forest had a different fate.
Mount St. Helens unleashing its pyroclastic fury. Photo: USGS.
Mudflows from the volcano were rich in minerals, particularly silica. As they ripped through the forest, silica-rich water permeated the bases of the giant redwoods. This killed the trees by preventing the roots from receiving nutrients and carbon dioxide. By counting tree rings in specimens like the one at Disneyland, it is estimated that many of these trees were between 500 and 700 years old when they were killed. However, the minerals infused the stumps, permineralizing them by replacing organic matter cell-by-cell with silica. They were petrified and remained as they stood for the next 34 million years. The volcano eroded away to nothing, the lake disappeared, and the environment became colder and drier over time, but the petrified trees remained.
Since the late 19th century, visitors have come to the see and study their remains. The first formal geological surveys of the site took place in the 1860's and 1870's. Eventually one lucky tree was purchased by Walt Disney and moved to a place of honour in Disneyland. So the next time you are rushing from Pirates of the Caribbean to Big Thunder Mountain, pause for a moment before this relic of a bygone age and contemplate the dramatic story this one fossil tells us about the history of North America.