Not too long ago at a theme park not too far away, Star Wars: Galaxy’s Edge opened at Disneyland—and soon at Walt Disney World—transporting people to Black Spire Outpost on the planet of Batuu. While the tall rock spires of Batuu enhance the other-wordly experience, they take their inspiration from some very real rocks here on Earth. In this video, I’m going to discuss the geology that inspired the planet of Batuu and Star Wars: Galaxy’s Edge.
The tall rock spires of Batuu are designed to be giant petrified, or fossilized, trees. Black Spire Outpost gains its name from the 135-feet-tall petrified spires of once giant trees, one of which is a striking dark black color. As described by the Disney Parks Blog, “Widely known for the petrified remains of its once towering ancient trees, the spires now stand guard across the river valleys and plains and have long captured the imagination of travelers to this planet.”
These petrified tree spires were largely inspired by Petrified Forest National Park, located in northeast Arizona. Although at Petrified Forest National Park, you won’t find anything visually reminiscent of a forest or see any tall ancient tree spires. The petrified trees here are all fallen logs or stumps that have fragmented over time.
Around 215 million years ago, this area in present day Arizona was a sub-tropical forest with 200 foot-tall trees in a basin with flowing rivers and streams. Over time, trees would die and fall into the streams, and some would become petrified, or fossilized.
In order for an organism—either plant or animal—to become a fossil, it first must die and then be rapidly buried. Upon death, most organisms decay or are subject to scavengers, leaving no material or fossil behind. But rapid burial can cut off oxygen, slowing or stopping decay and helping the preservation potential.
The trees that became petrified here were buried quickly and deeply in the sediment of the ancient rivers, which inhibited decomposition. Part of the petrification process—actually becoming a fossilized tree—involves a step call permineralization. Permineralization is where minerals are deposited in the cells of an organism. In the case of these trees, silica dissolved from volcanic ash was carried into the trees through groundwater, forming quartz within the tree’s cells. The trees then underwent the final step in petrification, replacement, where all organic material was fully replaced by minerals like quartz. You’ll notice that the petrified trees are various hues of red, orange, blue, and gray—this is due to mineral impurities like carbon, copper, and iron. The full fossilization process can take up to millions of years, although it can occur more quickly. Erosion over time then re-exposed the petrified trees.
If you’d like to see a real petrified tree, you don’t have to travel far! Located in Frontierland near the Rivers of America, you’ll find the remains of a real petrified tree. Gifted to Disneyland by Lillian Disney in 1957, this petrified tree stump comes from the Florissant Fossil Beds National Monument in Colorado and was likely once part of a 200-foot-tall tree.
The plaque by the tree, unfortunately, does not have the most accurate geological explanation for its origins, stating that it formed “55 to 70 million years ago” and that “During some prehistoric era a cataclysmic upheaval caused silica laden water to overspread the living forest.”
In reality, this tree was part of a forest 35 million-years-ago, and we can thank its preservation primarily to explosive volcanic eruptions. At the time, nearby volcanoes spewed out loose ash and debris onto their flanks. When intense rainfall mixes with this loose volcanic material, it can create extremely fast-moving and deadly mudflows called lahars. A lahar mudflow was triggered and traveled from the flanks of the volcano toward the forest valley, rapidly depositing muddy ashy material, which trapped the tree trunks in place, killing them and cutting them off from oxygen. The trees were then petrified when dissolved silica derived from the volcanic ash precipitated into the wood cells and the organic material became fully replaced by quartz.
So all in one trip to Disneyland you can explore Earthly and other-worldly petrified trees! If I had to imagine how the massive petrified tree spires of Batuu came to be, I could picture there being massive volcanic eruptions millions of years ago that buried the giant trees in over a hundred feet of ash. Huge volcanic eruptions with pyroclastic flows and lahars could destroy an entire forest. Many of the petrified spires appear to be in situ—meaning in place—so they appear to have been fossilized right where they grew. Some trees in the Resistance Forest area do appear to have fallen over and were later buried and fossilized, like the trees of the Petrified Forest National Park. Volcanic ash is compacted into a rock called tuff, which would encase the trees spires as they petrified over time. How might one spire become so much blacker than the others? It could have taken in a lot of carbon impurities during petrification, which would have led to a dark black color. The area would have to experience large amounts of erosion to erode away much of the tuff and expose the hardened petrified spires. You can even see relict dwellings carvings in the rock, much like the pueblos carved into the tuff at Bandelier National Monument in New Mexico.
Next time you travel to Batuu, you’ll now be an expert in the origins of the spires that give Black Spire Outpost its name, and know about the Earthly counterparts that inspired them.
May the spires keep you!
Emily Zawacki, Ph.D. 