Thirteen thousand years ago, Utah got cold–really cold. The last ice age had been over for at least 5,000 years, but after a sudden drop in temperature, the climate—heading towards warmth and dryness—flipped a U-turn. As snow and ice crisscrossed the state, the sudden increase in precipitation triggered a massive eighteen-mile-long train of landslides that altered the natural topography of parts of central Utah.
For the past four years, geology professor Steven Nelson has studied these landslides and the wetlands that were created atop their uneven surfaces. He observed the geographical landscapes, located near Capitol Reef National Park in Utah, to understand the historical climate patterns of Utah and the western United States.
While a BYU graduate student, Nelson had mapped these landslides but never studied them in depth. After he returned to his alma mater as a professor, Nelson decided to dig a little deeper. He began to remove long, two-inch-wide shafts of earth from the ground, also known as “coring,” to gain a closer look at microscopic materials deposited throughout the years.
“I wrote about these landslides in my master’s thesis. I had no idea how old they actually were,” Nelson said. “The initial idea was to only core the bottom and get the age on the lowermost sediment to find out how old the landslide was. But when we split the core open, I started looking at what was inside and there are these fantastic looking critters.”
These “fantastic looking critters” are single-celled algae called diatoms. Nelson knew very little about them when he began looking at the cores.
“I actually took a month-long course run by the University of Iowa at the Iowa Lakeside Laboratory and learned [about] diatoms,” Nelson said.
Most people have seen diatoms if they’ve ever spent time around a pond. It’s the brown fuzz that grows underwater around the plants.
“The reason they’re brown is because their chlorophyll is brown, not green,” Nelson said. “They actually make their cell walls out of pure silicon dioxide (biogenic glass), and so their cell walls are really, really, well preserved in the sediment.”
The diatoms’ preservation lends itself to learning about the past climate patterns of wetland locations. A key indicator for these climates is water, specifically how much and how often it remained in a wetland.
“Some diatoms will only live when there is standing water all year. Some diatoms will grow in the soil, but they can’t tolerate standing water,” Nelson said. “The diatoms you have at the core will tell you when it’s wet, when it’s dry.”
By looking at the types of diatoms and their location in the core, Nelson and his colleagues mapped out the fluctuations of the climate in the Western U.S. He has also determined the age of the primary landslide he was initially focused on.
“The ages at the bottom [of the core] tells us the landslide moved from between 12,500 to 13,000 years ago,” Nelson said. “That maybe sounds like a long time ago to you, but to a geologist that’s just yesterday.”
When the climate briefly returned to almost glacial conditions, the cold, wet, saturated ground primed the terrain for descent.
“The climate cooled as it had been during the ice age, stayed there for 500 to 1,000 years, and then warmed back [up] and continued warming,” Nelson said.
Hills and cliffs collapsed within this relatively short period of time and nature correspondingly forged new ponds and wetlands on top of the landslides. Those wetlands allowed Nelson to understand what happened to the climate next.
“Although there was a lot of volatility in the climate from 10,000 to 12,500 years ago, it was, on average, wetter with brief dry periods. So it was more pond, more standing water than wetland,” Nelson said.
That pattern switched for a few thousand years when the wetlands saw more dry periods than standing water. It was followed by a montage of precipitation patterns. Recently, the western U.S. is in the midst of a cool period, which is being undone by the human release of greenhouse gases.
“In the last 2,000 years, it has been colder and wetter in the winter in the Western U.S.,” Nelson said.
According to Nelson, there’s an incredible applicability that can be derived from all this information collected.
“One of the ways climate scientists evaluate climate change is to run climate models to try and predict the future,” Nelson said. “You can run the model in reverse to see if the model produces changes in precipitation that match what’s recorded in the [wetlands], because if you can predict the past, you have greater confidence that your models can predict the future.”
Essentially, climatologists can use Nelson’s data to ensure the accuracy of their future climate predictions.
Of course, as a geologist, Nelson’s research is less about future and more about the past. His driving motivation to conduct research is a desire to learn and find answers to geological questions.
“It’s fundamental science,” Nelson said. “We like to know how the earth works.”
Note: This article was originally written in our published science magazine Frontiers. Read the magazine here.