FEE SCHEDULE EFFECTIVE MAY 1, 2015::
ADULTS $9.00 per person
HAYS COUNTY RESIDENTS (proof of residency, photo ID required) $5.00 per person
CHILDREN AGES 5 - 12 $5.00 per person
CHILDREN AGES 4 and Under FREE SENIORS 60+ $5.00 per person
SERVICE MEMBER/VETERAN $5.00 per person
Jacobs Well Natural Area Swim time Booking only allows 300 people per day. Those wishing to swim must reserve a 2 hour block of time by using the online reservation system.
Jacob’s Well Natural Area Jacob’s Well is the First Hays County-owned nature preserve. It is the most significant and largest continually flowing karstic spring in the Texas Hill country. A Karst Spring is a spring that is part of a system that includes the underground drainage of a much larger area, which means that these types of springs often have a very large discharge area. They are typically located at the end of a cave system at the place where a river cave reaches the earth’s surface. This is often achieved through Limestone erosion of the area at the spring source when outside forces mix with the spring water. Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3) This mineral is composed of skeletal and calcium fragments of marine organisms such as coral or foraminifera.
There are several Types of Limestone rocks: Chalk, Coquina, Fossiliferous, and Tavertine.
Chalk – Type of limestone created from the calcareous shell and small marine organism. The texture is very soft and fine.
Fossiliferous – This type is created from the shell and skeletal fossils and takes a very long time to dissolve. This one of two types of Skeletal Limestone is pourous yet strong.
Travertine – This 2nd of two types of skeletal limestone has a lighter coloration than its Fossiliferous brother and lacks the same porous characteristic, appearing as solid as marble.
Coquina- Type of limestone that is created by broken shell debris and is very coarse. Typically found on the beaches and is arguably the least amount of time in transformation from dead organism to limestone.
Limestone is generally not very soluble, so the rock wouldn’t dissolve very quickly under most circumstances and typically doesn’t in a freshwater spring. However slightly acidic rainfall, formed by carbon dioxide dissolving in water, interacted with the limestone rock in this spring over several millennia, slowly eroding and dissolving the limestone and forming an underwater cave system that is that is now home to many species of salamanders, crawfish, amphipods and isopods. The 12ft (4m) diameter opening to the cave starts at about 5ft underwater and then descends vertically followed by a limestone-eroded cave system at an angle for about 4500ft (1372m). This is well over a mile of explored underwater cave passages!
TO OBTAIN CREDIT FOR THIS CACHE, YOU MUST EMAIL ME THE FOLLOWING ANSWERS
: 1. What does the word “Karst” mean and why do you think this has formed here?
2. Peep down into the Spring from either the dock alongside it or the rock trail above it. Estimate how deep the limestone opening has eroded before the cave system starts and what physical evidence do you see of the cave widening and expanding?
3. What is the name of the solution that has interacted with the springwater and dissolved the limestone rock? (hint: rain combined with what to form what kind of acid?)
4. Walk down the path to the edge of the opening. Notice the limestone colorations and texture up close to determine the answer: Based on your observation, what type of Limestone rock in the description above do you see of this Karst Spring? What about the walls that raise above it? Describe why you think that with your observation information.
OPTIONAL:: 5. Post a photo of yourself with the opening of the cave in view, swimming IN the opening of the cave, or jumping into the opening of the cave! (Due to new groundspeak rules a photo is not required but highly encouraged!)
I hope you enjoy this Earthcache and this beautiful natural area. Be sure to enjoy the hiking trails and other geocaches in the area, as Jacob’s Well Natural Area encourages and advertises geocaches as part of their experience!