What is a Petrified Forest?

A petrified forest is a forest made out of fossil or petrified wood. In other words, it is a forest made out of stone trees. Petrification is a natural process that occurs when all organic material in a tree dies and is replaced by a combination of quartz, copper, iron, and other minerals. Once the process has been finalized, petrified wood is no longer considered wood, and it becomes classified as a stone. In fact, petrified wood is Washington's official stone. All petrified forests are national monuments and are carefully protected.

A petrified forest becomes such over the course of million of years. Some of the world's largest ones are an estimated 100 million years old. Volcanic ash is sometimes a key step in the process of petrification. In fact, it's not uncommon for a petrified forest to have been covered by mud made out partially by volcanic ash at some time. Volcanic ash produces a chemical reaction in the wood, which in turn accelerates the process of petrification.

A petrified forest can take different colors, depending on the type of material once absorbed by the living trees. Cobalt and copper cause a greenish blue tint, while manganese turns the wood pink, and carbon produces gray. Some trees have more than one color, while others are basically composed of crystal quartz, which are transparent and allow for a view of the grain wood.

The world's most impressive petrified forest is in Santa Cruz, Argentina. With trees that are over 10 feet (3 meters) in diameter, the Patagonian petrified forest is one of the best giant examples of wood-stone in the world. As a comparison, the Petrified Forest National Park in northeastern Arizona, considered the best example of petrified wood in North America, boasts trees that barely reach six feet. Canada has the largest forest of this kind in the world, covering an area of thousands of kilometers and dating back to the Eocene period.

A petrified forest is a natural phenomenon where fallen trees have fossilized over millions of years, turning into stone through a process called permineralization. Minerals carried by groundwater replace the organic tree material, creating a detailed stone replica of the original wood, often preserving the tree's structure and cellular details.

The petrification process can take millions of years. The exact time frame depends on the conditions present, such as the type of mineral-rich water and the rate of sediment burial. According to studies, the optimal conditions can lead to the beginning stages of petrification in a few hundred years, but complete petrification is a much longer process.

Petrified forests are found worldwide, with notable examples including the Petrified Forest National Park in Arizona, USA, and the Petrified Forest of Lesvos in Greece. These forests can exist in regions with volcanic activity or anywhere with the right conditions for wood to be buried rapidly and mineralized over time.

Removing petrified wood from national parks or protected areas is illegal and can result in significant fines. These natural artifacts are preserved for scientific study and public enjoyment. However, there are some private lands where you can legally collect petrified wood with the landowner's permission.

The most common minerals involved in petrifying wood are silica, calcite, pyrite, and even opal. Silica, often in the form of quartz, is the predominant mineral that replaces the organic material, leading to the creation of beautifully preserved petrified wood with a variety of colors depending on the trace minerals present.

Petrified wood provides a valuable record of ancient ecosystems, helping scientists understand the climate, vegetation, and conditions of the Earth's past. It can offer insights into the types of plants that existed in prehistoric times and how they have evolved or become extinct, contributing to the field of paleobotany.