Care and protection of fossil wood around the world. Let's explores the factors behind the weathering process.
Many people mistakenly assume that petrified wood is as durable as stone and are unaware of its potential for deterioration. However, when petrified wood is preserved underground for extended periods and then excavated, it becomes exposed to changing environmental conditions, leading to sudden effects such as breakage and decay, commonly known as "post-excavation shock." Both extreme heat and freezing temperatures have the potential to degrade petrified wood, highlighting the importance of understanding and preserving these natural treasures in various environmental contexts. To ensure the care and protection of fossil wood, it is important to consider these factors and implement measures such as proper storage, controlled environmental conditions, and preventive conservation practices. Additionally, regular monitoring and prompt treatment of decayed areas can help preserve and extend the lifespan of these valuable specimens.
Petrified wood deteriorates due to temperature and humidity changes. In Thailand, summer temperatures range from 40-50°C (104-122°F) during the day to 25-30°C (77-86°F) at night. Exposure to sunlight, rain, and wet-dry fluctuations, along with occasional flooding, contribute to decay. Conversely, in places like the Florissant Fossil Beds National Monument, cold winters and freezing temperatures affect wood stability. Freeze-thaw cycles from water seeping into cracks and freezing can cause further damage.
Water, Moisture, and Soluble Salts
Water, originating from air moisture, groundwater, and rainwater, plays a significant role in petrified wood decay. It carries soluble salts into the wood's small spaces. Sources of salt include soil constituents, dissolved salts in groundwater, environmental pollutants from living organisms, and even salt present in construction materials like cement.
In hot weather conditions, water carrying dissolved salts evaporates, leaving behind concentrated salt deposits. As water continues to evaporate, salt concentration increases, leading to the crystallization and expansion of salts within the petrified wood. This expansion creates pressure, causing the wood to split apart, a process known as salt decay. Therefore, materials like cement and concrete are unsuitable for conservation applications.
Human and Animal Interference
Human activities, such as handling petrified wood as souvenirs, walking, sitting, scrubbing, or even minor touch, contribute to its degradation. Bird droppings, containing uric acid that corrodes the wood, also add to the damage. Sunlight intensifies the corrosion process, dissolving salts and accelerating their penetration into the petrified wood.
Mechanisms of Decay.
Corrosion from Mineral Compounds
Decayed portions of petrified wood exhibit various compounds, resulting in orange, brown, and red bands. The darker bands contain higher iron content, while the pink-red parts consist of iron oxide (hematite). Yellow and brown bands represent iron oxide hydroxide (goethite). These bands indicate the diffusion of iron compounds during the decay process.