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Zoe Hern Rochelle Johnson Gipson First Year Seminar 1 December, 2016 Petrified Wood: Hydrated with History Fossils have a lot to say about the past. They tell a unique story. Such stories are valuable, considering only a small fraction of living organisms have been preserved in stone. But fossils are not exclusive to dinosaurs and other immensely interesting vertebrate. Plants are also fossilized, and reveal groundbreaking information about the history of the Earth. By examining petrified plants, one not only discovers how the world formed the object, but how this thing has shaped the world. Petrified wood has meaning, and by understanding one specimen’s journey, I have uncovered significance. Petrified woods, such as the specimens in the Orma J. Smith Museum of Natural History, are literally wood turned to stone. They are not impressions in clay, like most fossils, but rather have undergone a chemical process where minerals actually replace the organic material while retaining the tree’s natural structure in a kind of cast. This process is called permineralization (Daniels 25-27). The more wood-like structure is preserved, the more impressive truths a specimen holds about the ecological, environmental, geological, and anthropological story of its region of origin. Some pieces, however, are completely or nearly fully converted to rock. The better preserved a petrified specimen is, the greater the monetary and scientific value (Emry). In extreme cases these lack all the tree rings and cell impressions that are key to identifying the tree species and reconstructing an ancient climate – though they do make beautiful jewelry or show pieces. 2 Fossils are formed when a living organism is quickly buried alive and immediately sealed off from the air. The process could occur during a flood, landslide, glacier, or volcanic eruption. This particular specimen of petrified wood was buried under volcanic ash and opalized. Rather than being burnt and covered by magma, a volcanic eruption spews silica-rich ash (SiO2), which falls from the air and dusts the landscape. The force of the explosion also knocked down many trees. Then in order to be opalized, “Water from rain or a stream” then hydrates the ash and “dissolves the silica into salt-like ions and enables them to soak into trees” (Goode). Nate Carpenter, a fossil expert, says that exactly this happened in Grassy Mountain. Silicon dioxide particles in the ash fell into some hot springs and permineralized logs that were trapped at the bottom of the springs (Cummings et al. 679). In some places, the trees were blown into the ancient stream or lake that existed, when another eruption covered the water in magma, burying the hydrated vegetation (Carpenter). In this anaerobic situation, the organic material stops decomposing, and eventually the ionized water evaporates, leaving behind solid deposits of silicon dioxide and small traces of other soluble salts, like ferric (iron) oxides (Goode, Carpenter, Tormey). These silica molecules form a crystal structure as they are distilled and compressed (Tormey). “When the particles are of similar size and form near perfect crystal lattices, light is scattered so all colors of light are reflected” – this is precious opal (Tormey). More common, however, the particles are amorphous in size and line up irregularly, diffracting light and giving it a milky white or grey color (Tormey). This common opal is the variety that formed inside this particular specimen. By looking 3 closely, one can even see traces of red in this petrified wood, indicating small amounts of ferric (iron) oxides that were in the volcanic ash. This piece also holds an incredible history of geologic evolution. It was found near Grassy Mountain in Vale, Oregon, just north of the Oregon-Idaho graben. A graben is a geological formation where an area is depressed in a kind of valley, having two parallel faults on either side. This formation evolved during North America’s tectonic drift westward during the Miocene, and the Owyhee County (south of the fault) actually rested above the Yellowstone hotspot (Cummings et al. 669). As the continent drifted, molten materials rose near the surface and probably touched underground lakes (Cummings et al. 674). This caused the water to turn into steam, creating pressure underneath the crust, multiplying the stress already occurring as the tectonic plates shifted. Lava flowed through buttes and rhyolite volcanoes, creating “tuffaceous silt and mudstone” formations surrounding the graben about 15.3-14.3 million years ago (Cummings et al. 672). Then, 14.3-12.6 million years ago, calc-alkalic volcanoes (having more fluid lava with low silica concentrations) became extremely active, creating massive basalt flows (Cummings et al. 674). Approximately 13.1 to 12.6 million years ago, Grassy Mountain spewed lava with high silica content, resulting in the permineralization of vegetation (such as this tree) and eventually forming precious crystalline structures (Cummings et al. 677). Grassy Mountain was a fairly dangerous rhyolite volcano because it spat high concentrations of silicon dioxide (SO2) (Harris 31, Cummings et al. 677). These eruptions petrified this exact piece of wood. Fossilization no longer occurs along the Oregon-Idaho graben because as this area moved further and 4 further from the Yellowstone hotspot, eruptions became less frequent until every butte became dormant. Petrified wood from Grassy Mountain Vale also has much to tell about the Eastern Oregon paleoclimate. Though the dry, seasonal Eastern Oregon climate was about the same when this fossil was formed, petrified wood is capable of showing important trends about the climate. By examining this piece, one can see that the tree rings reflect seasonal temperature changes. It is also likely an oak – oak trees do not grow in moist areas, so we can deduct that this area was about as dry as it is today 12 million years ago. One can even estimate the region’s Milankovitch cycles in relation to climate change. Milankovitch cycles rationalize climate and seasonal change on an astronomical scale. The position of earth in relation to other planets (like massive Jupiter) could result in a slight gravitational pull, varying the earth’s orbit about the sun ever so slighty. Expert in geology and climate, Jaime Goode, says this small adjustment could make winter colder, summer hotter, vice versa, or “even affect when seasons occur” (Goode). So the distance between tree rings correlate to the temperature of the year, scientists can estimate the positions of planets millions of years ago – especially if the rings are distinctly visible – and of course, confirm their findings by consulting other disciplines. Scientists similarly scrutinize the variety of petrified species (Carpenter). Some fossilized wood from Eastern Oregon dating before the Miocene Epoch are trees that only grow in warm, tropical climates – they cannot handle freezing temperatures – supporting the theory that large Pacific islands collided with the North American mainland, creating the Washington, Oregon, and Californian west coast (Carpenter). Before the Pacific and Juan de fucca plates met, Eastern Oregon was beach-front property, allowing for such a wet 5 climate. The Petrified Forest in Arizona, another example, was also once a humid and moist climate – probably due to a vastly different tectonic position about 200 million years ago. These small details prove immensely important in analyzing past climates. Petrified wood from any area can even reveal much about a region’s ecological history. Daniels recorded that “[a] 1962 study [near the Oregon/Idaho border] identified fossilized remains of trees representing sixty-seven species,” ranging from common varieties common in the east coast area to the Ginko and Metasequoia (13). This evidence proves that Eastern Oregon once had very diverse vegetation; now it basically supports a variety of weeds. Carpenter explains that the variety of trees and their position can also reveal the elevation if a lake or stream was nearby. For instance, sycamores thrive near water, so a petrified sycamore indicates the existence of a long gone body of water; on the other hand, oaks and pines cannot live too near bodies of water and prefer dryer areas, so this fossilized oak reveals the absence of water when it was petrified. Tree variety also indicates a region’s elevation because each species is restricted to a certain elevation level: if a petrified birch tree is discovered high upon a mountain, we can deduce that the birch was petrified before the mountain formed and altered the ecosystem. Petrified tree resin also can preserve insects. Tropical bugs have been found in fossilized sap from very cold regions, suggesting that at one time, such a place had a much warmer climate. Petrified tree pollen, usually found in lake beds, also can indicate the kind of trees and vegetation that thrived in areas where fossils are scarce. Nature inscribed its history in petrified wood, and speaking the language allows us to make connections to the world’s evolution. 6 The value of petrified wood explains the story of people. Many Native Americans used petrified wood to create arrowheads and spearheads, making hunting and warfare more effective. It was also shaped into game balls, tools, and used for building materials. Some tribes also cherished spiritual legends relating to the rock. For instance, the Navajo believed the logs in what is now Petrified Forest National Park to be the bones of the evil monster-god, Yeitso, who was defeated in an epic lightning battle (6, Daniels). Yeitso was the offspring of Tsohanoai (the sun god) and Naste Estsan (the spider goddess who taught humans how to weave), and was the chief of the Anaye – a race of giant bloodthirsty monsters who were born from “unnatural sex acts” between either gods and human women, Yeitso and his mother, or as a result of lonely women impaling themselves with odd objects (6). Though there are many variations of the legend of Yeitso’s defeat, the common story explains many natural processes (like the sun’s cycle), how many animal and plant species came about, how precious stones were dispersed, and even encourages bravery and courage in warfare (6). The Paiute peoples believed that the Petrified Forest in Arizona was a battle site between “the Thunder God Shinauave and his enemies,” and that the petrified logs “were spent arrow shafts and spears” (Daniels, 7). Petrified wood was/is also made into beads to make jewelry, and jewelry was, and still is in many places, a form of currency. Beautiful gems like this art piece were created through natural processes, and artisans continued the ancient tradition begun by the earth, and refined the stones into polished accessories. Petrified wood has wedged itself into human culture through this art. But petrified wood was also important to famous European thinkers. According to Daniels, “Leonardo Divinci…used his knowledge of [petrified wood] in developing theories regarding the formation of the earth,” and Darwin 7 used it as evidence to support his evolution theory in relation to landscapes (7-9). The idea of evolution is not a new concept, and understanding petrified wood has allowed thinkers to look into the past and question the origins of the world hundreds of years ago. After examining the chemical, geological, environmental, cultural, and historical story behind petrified wood, it is clear that this is more than a simple rock. Understanding the formation process of this fossilized specimen is key to unlocking the secrets of the natural past, which is important in rationalizing present happenings. Petrified wood pieces are the most important evidence in determining “when did this mountain get here, was there a lake that was buried by lava, how diverse was the ecosystem at one given period” etc. And this specific piece, probably oak, leads to complex explanations of paleo-Oregon: this tree did not live near a body of water; the landscape sustained more than just weeds; stress beneath the earth and multiple volcanic eruptions reformed the landscape over and over again. Petrified wood embodies natural change because it reflects the continuous evolution of the land; death, because the tree suddenly, unexpectedly died one day; immortality, as the specimen was preserved and is admired millions of years after it’s death; beauty, and wisdom. Emry states that “the value of a petrified wood specimen depends on the quality of preservation, the clarity, size, what is known about the piece, and the beholder.” A clear specimen lends itself to be identified as a species and has sharply preserved cells and growth rings. Knowing where the specimen was found is also important to the value: “the better story you can tell about it, the more it’s worth” (Carpenter). This includes scientific and monetary value. A collector might value a piece more from Montana than Eastern Oregon; a jeweler might pay more for an colorful specimen, while a geologist is 8 more interested in the wood-like piece that holds knowledge. Size is also important, as a larger specimen is much more rare than a pebble-sized one. In geology, no specimen is quite like the other; each is unique, so each is worth collecting (Emry). Perhaps petrified wood holds personal value as well. When looking at this petrified specimen, I see myself. Its home was in Eastern Oregon, not far from where I grew up; I see my great-grandfather who collected precious rocks and petrified wood, leaving much of his collection to me; I see the beautiful volcanic formations that I journey through from my home to Caldwell; I see simple beauty, structure, and rigidity – like my personality. This piece is a reflection of myself. What if every tree fossil is a picture of an individual: could petrified wood universally be the looking glass to humanity? Petrified wood is valuable, not only because it is a result of a rare chemical process, but because of the knowledge it holds. Secrets about the environment in days long before humans, cultural monuments, and the formation of the earth are imbedded within the wood’s crystalline structure. Petrified wood forces us to question the origins of the earth and prompts us to investigate the development of the earth and how it is changing. It reveals to us new chemical processes that drive environmental change in landscapes and organisms. This petrified wood specimen acts as a reminder of how an ancient opalized rock has molded world history. Petrified wood is a tangible idea that was born before the scope of human existence. Beholding this object is beholding our imagination: its journey encompasses factors that are only limited by our minds. 9 Works Cited Carpenter, Nathan E. Meeting interview. 30 Nov. 2016. Cummings, Michael. “Stratigraphic and Structural Evolution of the Middle Miocene Synvolcanic Oregon-Idaho Graben.” Geological Society of America Bulletin. May, 2000. 21 Nov. 2016. <https://www.researchgate.net/profile/Michael_Cummings6/publication/2799465 70_Stratigraphic_and_structural_evolution_of_the_middle_Miocene_synvolcanic _Oregon-Idaho_graben/links/55ce530308ae6a8813849e26.pdf> Daniels, Frank J. “Petrified Wood: The World of Fossilized Wood, Cones, Ferns, and Cyads.” First Edition. Western Colorado Publishing Co, 1998. Emry, Howard. Meeting interview. 30 Nov. 2016. Goode, Jaime. Meeting interview. 21 Nov. 2016. Haris, Stephen L. “Fire Mountains of the West: The Cascade and Mono Lake Volcanoes.” Mountain Press Publishing Co, 1988. Tormey, Nathan. Meeting Interview. 18 Nov. 2016. Wozniak, Edward and Balladeer. “Navajo Myth (Clear).” Glitternight. 2010-2012. 25 Nov. 2016. <https://glitternight.com/navajo-myth-clear/>