At 6,300 feet in elevation, and located at the base of Desolation Wilderness, sits a forest unlike any other. I’m sure for some of you, the thought of a forest at this particular location doesn’t sound all too interesting.
But, what if I told you that this forest is underwater? I bet that’s grabbed your attention.
In addition to the intriguing examination of how the lake got its name, is an even greater mystery that sets this alpine body of water apart from any other lake in the state – the underwater forest of Fallen Leaf Lake.
Fallen Leaf Lake
Fallen Leaf Lake was formed out of two glaciers that are believed to have traveled north and stopped roughly one mile south of Lake Tahoe. A terminal moraine, which marks the end of the glaciers’ movements, is noticeable on the north end of the lake.
If the glaciers didn’t stop, they would’ve continued into Lake Tahoe and formed another bay just like Emerald Bay, which is roughly three miles northwest of Fallen Leaf Lake.
Instead, we have a picturesque alpine lake that’s 152 feet higher in elevation than Lake Tahoe, nearly three miles long, and nearly 415 feet deep at its deepest point. On average, the lake is 240 feet deep.
The cold, potable water has become a perfect mechanism for preserving early 19th century items and ancient trees found in the depths below.
How did an Underwater Forest Grow in Fallen Leaf Lake?
There are two theories as to how these trees ended up standing perfectly upright underwater as if they magically grew from the lake’s bottom: a megadrought or a landslide.
The Megadrought Theory
In the late 90s, an experienced scuba diver and a professor first “discovered” these underwater trees and began documenting their locations.
Professor Kleppe sent down a camera on a ROV (Remotely Operated Underwater Vehicle) and began taking pictures of an incredible underwater forest.
Kleppe’s efforts spawned even more scientific explorations to study these remarkable trees like the one in 2009 by Graham Kent the director of the Nevada Seismological Laboratory.
Kent went beneath the water in a two person submersible and became the first documented person to see what he called a “ghost forest.”
He would further describe the scene as follows:
“It was a bizarre Christmas-tree effect. I was just waiting for Rudolph the Red-Nosed Reindeer to come flying in.”
Kent used side scan sonar technology to map the Fallen Leaf Lake underwater forest and also discovered that the lake had undergone significant changes in the past especially with the water levels. He was also able to rule out that an earthquake cracked the lake’s floor.
Researchers have long believed that the Sierra Nevada region has gone through megadroughts in the past. A megadrought is defined as a drought lasting at least two decades or longer.
The drought at Fallen Leaf Lake is believed to have taken place between the 9th and 12th centuries and to have lasted up to 200 years.
Sonar was able to confirm an ancient shoreline which also leads scientists to subscribe to this megadrought theory as they believe that the lake fell 130 to 200 feet during this drought.
In 2009, Kent surmised that these ancient trees and the shoreline levels are evidence that megadroughts can occur every 650 to 1150 years. He also ruled out a landslide as possible reason for these trees standing upright at the bottom of the lake.
Yet, seven years later, another underwater voyage provided evidence that could prove the megadrought theory inaccurate as it challenges Kent’s belief that a landslide couldn’t have caused this underwater forest.
The Landslide Theory
In 2016, Tom Loomis, scientists and the Undersea Voyager Project dove into the cold waters of Fallen Leaf Lake and helped shed light on another possibility for this mythical looking underwater forest.
These expeditions in the summer of 2016 believe that seismic activities at least a thousand years ago led to the trees sliding into the lake and becoming a submerged forest.
The Tahoe-Sierra Frontal Fault Zone is comprised of five different faults. Additionally, three faults are deeply positioned under Lake Tahoe. It’s believed that seismic activity is what caused the formation of the Tahoe Basin and not glaciers.
Furthermore, the 2016 exploration concludes that seismic activities are what caused Fallen Leaf Lake’s underwater forest.
One factor supporting that conclusion is that there are trees standing next to each other varying in age. In fact, some of these trees are thousands of years apart in age. Yet, they’re all in perfect condition.
If they grew in the lake during the megadrought then there would be signs of a deterioration on the older trees due to the drastic fluctuation of water levels during prolonged droughts. That’s not the case here as there is no evidence of this.
Another factor supporting the landslide theory is that many of the trees had roots that were torn off. That wouldn’t happen if they grew in that area during a drought. But, that would happen if the trees fell into the lake due to a landslide.
Even with damaged roots, the trees still stand perfectly upright at the bottom of the lake. Some of these trees are over 100 feet tall.
In addition to documenting this forest, the Underwater Voyager Project and Kent’s study also detailed a jellyfish like specimen that lives down in the depths of this lake.
Scott Cassell, team leader of the Undersea Voyager Project, has been transparent with every dive they made. He acknowledges that megadroughts existed in this region, but that they’re not the cause for the underwater forest at Fallen Leaf Lake:
“There’s no doubt megadroughts have occurred in the past and that the lake level at Fallen Leaf Lake has dropped and risen many times. We’re simply examining whether or not the trees grew there during one of those megadroughts or if these particular trees got there in some other way. So far, all of our evidence on the ancient trees supports the theory that they did not grow there.”
How Old Are These Trees?
Although scientists and researchers debate how the origin of the underwater forest, they don’t debate how old some of these trees are. Kent originally stated that these trees are up to 3,000 years old. Cassell and his team did not dispute this conclusion in their research.
Did They Find Anything Else Underwater?
In addition to the trees and a previously unidentified jellyfish like species, Cassell’s expeditions noted how they saw artifacts from the 1800s, like shoes, perfectly preserved. He surmised that due to the water being so cold, the decomposition of these items is very slow:
“We’ve found some shoes and other artifacts from the turn of the century that look like they were lost yesterday.”
In the video of their exploration, you can see some of these artifacts that Cassell is alluding to. Furthermore, these items are in the lake because residents used to dump their garbage in Fallen Leaf Lake back in the late 1800s.
For more on this region of Lake Tahoe, check out the following articles: