There are many professions in which I probably dabbled in a past life (or several past lives). Meteorologist, ornithologist, playwright, psychologist. So many different things catch my interest that it’s hard to pick just one thing to be passionate about.
One particular area of study I’ve always been interested in was geology. While I’m nowhere near as skilled as my paleontologist co-blogger, Tara, I’ve learned to take advantage of her knowledge and have picked up a deep appreciation for the stories told between layers of rock.
The cool thing about geology is that it is a universal story. It exists on every continent and in every ocean, and often provides bridges between lands that seem distant. It provides a window to the past and reminds us that nothing in constant. The Earth is a living, breathing, changing thing.
Amateur that I am, I regard most geological features with a certain sense of awe. Hamilton Pool Preserve, just west of Austin, Texas, is no exception.
The creation of Hamilton Pool
Visually, the Hamilton Pool is spectacular, even when the water levels are low. It’s no wonder that it is one of the most popular swimming holes in the state of Texas, with towering limestone walls and a deep, cold pool of water fed by a tumbling (or sometimes trickling) waterfall. It is definitely beautiful, and when I visited it recently this beauty was enhanced by the very beginnings of fall foliage.
This pristine swimming hole was once an underground river. The pool was formed when the roof of the river collapsed, creating what is known as a plunge pool. Don’t worry about further collapse — this happened thousands of years ago!
Why did the collapse happen at all? Through the power of undercutting.
Not all rocks are created equal. Some are softer, while others are more porous. Certain rocks, like shale, are very smooth, while sandstone has a grainy quality. Rocks also erode at different rates. The softer the rock, the more quickly it erodes.
When you have a hard rock on top of a softer rock, and then stick a waterfall on top of those rocks, you have a recipe for eventual disaster. The splash-back from the waterfall slowly erodes the bottom layers of rock away, while the top layer erodes much more slowly. Eventually, the resulting open space can’t handle the weight and you have a collapse.
The result is a plunge pool: a waterfall that literally plunges downward from a ledge, with a carved out area of air behind it. These waterfalls are different from those that hug the limestone, like the karst falls in Croatia.
The result of the undercutting is an area of open air that allows you to walk behind the falls. This gives visitors some stunning views outward at the unique habitat formed by Hamilton Pool.
A glimpse into history – near and far
As I sat on one of the many limestone slabs that populate the area behind the waterfall (or watertrickle, as it were), I glanced upward. The ceiling of the alcove was dotted with prehistoric relics — shell imprints and fossils, from when the area was a shallow seabed. This pool was once covered by the same ocean that covered Dinosaur Valley State Park, where remnants of late Cretaceous dinosaurs allow you to literally walk in the footsteps of dinosaurs.
More recently, the nature preserve was the site of Native American tribes, specifically the Tonkawa and Lipan Apaches.
A unique ecosystem
By far the most stunning aspect of Hamilton Pool and the surrounding area is the ecosystem itself. This swimming hole is tucked into Texas Hill Country, where cacti are much more common than ferns. Generally, when hiking through Hill Country, you’re met with something that looks like this:
A lot of short, scruffy trees, tall grass, and prickly cacti. Quintessential Texas. Yet descend the 80 feet or so into the Hamilton Pool Preserve, and the scenery changes dramatically:
The views within this tiny ecosystem are stunning, full of bald cypress trees with water cascading over their roots. Ferns fan out, reveling in the abundant moisture, and the scent of various flowers hangs thick in the air. This area also is home to several endangered species.
Visiting Hamilton Pool Preserve
A visit to Hamilton Pool Preserve is definitely in order if you’re in the area. There are a few details to keep in mind, though, to ensure that you enjoy your time.
- The initial descent into the pool is about 80 feet, over limestone steps that have been cut into the rock face. It can get slippery, and it can be strenuous for those who are not used to it.
- Since its primary function is as a swimming hole, the preserve gets quite crowded in the summer. Park staff will limit the number of people allowed to visit, and you may get turned away. If you’re not planning on swimming (or don’t mind getting a little chilly) it might be best to visit during the off season.
- There is an admission fee of $15 as of this post. However, if you are camping at one of the nearby county or state parks admission is only $5.
- There are two trails in the Preserve. The shorter one, which leads to the pool itself, is .2 miles one way. The longer River Trail is .8 miles one way. This doesn’t sound like a lot, but the terrain does involve some climbing, so be prepared.
- Sometimes the swimming hole is closed for swimming, when the bacteria levels of the water become too high.
- There are chemical toilets at the top of the trail, and port-a-potties at the bottom. Be prepared for long lines during the high season.
- This is a nature preserve and, as with any outdoor space, respect is tantamount. Follow the Leave No Trace guidelines and don’t leave any trash behind, or disturb any of the wildlife. This includes picking flowers or berries.
- Have fun and, most of all, enjoy the beautiful scenery!