The Biscayne Aquifer EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(other)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
At the posted coordinates, you will have an excellent opportunity to view the geological make up of the Biscayne Aquifer as well as to study the water from within the Aquifer.
This EarthCache is in the Veterans Wayside Park. Park hours are Sunrise to Sunset. Please observe these posted hours and rules.
The Biscayne Aquifer
The Biscayne Aquifer, named after Biscayne Bay, is a surficial (near the ground surface) aquifer. It is a shallow layer of highly permeable limestone under a portion of South Florida. This aquifer is known as an unconfined aquifer, meaning that is does not have a confining layer on top of it (like clay) so rain water seeps right into it from above. The top part of the water in the Biscayne Aquifer is called the watertable (like the flat part of your dining table). See the below photo that shows its location in South Florida.
Background Geology
The water-absorbing layers of rock underlying south Florida are divided into three layers. The uppermost layer is the Miami Limestone (formerly Miami Oolite) which, as you may know, forms part of the Atlantic Coastal Ridge. The Miami Limestone is grainy, contains void spaces, and is very porous which allows water to be stored within it and also to pass through it. Water stored in the spaces in the soil, rock, and sand is called groundwater. This part of the aquifer is called the saturated zone. The groundwater in the Biscayne Aquifer is close to the surface (less than 15 feet in the Miami area), and because of this it interacts directly with natural and man-made bodies of surface water, such as streams, lakes, and canals.
The Biscayne Aquifer is Miami’s primary source of fresh water. The Biscayne Aquifer is the most productive of the shallow non-artesian (unconfined) aquifers in the area and is one of the most permeable in the world. This aquifer extends along the eastern coast from southern Miami-Dade County into coastal Palm Beach County as a wedge-shaped underground reservoir which is thickest near the coast (150-200 feet) and thins out to the west near The Everglades. It underlies The Everglades as far north as northern Broward County.
Hydrogeology (hydro- meaning water, and -geology meaning the study of the Earth) is the area of geology that studies the distribution and movement of groundwater in the soil and rocks of the Earth's crust (usually in aquifers). Scientists in Miami-Dade are tasked with understanding this relationship so they can better protect the Biscayne Aquifer from pollution spills onto the land surface, clean-up of any old or new contamination, and also how to obtain and treat water that is safe for us all to use in our homes. The below drawing shows you the relationship between the groundwater and the lake at he Park.
The EarthCache Location
Welcome to Veterans Wayside Park. At this location, you will see a small man-made lake which has been dug out of the limestone in this area. The water you see in the small lake is the actual groundwater of the Biscayne Aquifer. The water level in the lake is the same as the level in the surrounding limestone. This is because the bottom and sides of the pond are also limestone and is not impermeable (meaning, not paved like a swimming pool).
Therefore, Groundwater is free to enter the lake from the bottom and the sides of the lake. If it rained into the lake, that water would also pass out of the lake into the nearby groundwater, until the groundwater level and lake level were the same again. This water you see here is an example of the water that Miami-Dade County pumps out of the ground (usually from 60-100 feet deep), treats it well, and then pipes to our home.
At GZ, you will notice a step down to a limestone ledge. Be careful if you choose to step down. From this ledge you will be able to touch the very coarse limestone and study its voids/holes. This is typical of Miami Limestone, and we hope that this EarthCache helps you to see and understand more about the underground storage of groundwater (our drinking water source) in the Biscayne Aquifer. Enjoy your visit.
References include:
USGS
Wikipedia
The Groundwater Foundation
Completing the Earthcache To get credit for completing this Earthcache, please send your answers to the following questions to our profile Email. Incorrect answers may lead to further questions from us, or deletion of your find log. You may log your find after you have transmitted your answers.
1. Is the Biscayne Aquifer a confined aquifer or unconfined aquifer?
2. What is the water called that is stored in the spaces in the soil, rock, and sand?
3. From what you have read above, do you think that if someone spilled 1 Gallon of gasoline on the grass/soil in Miami, the gasoline would make its way to the groundwater in the Biscayne Aquifer?
4. Standing at GZ or on the lower ledge, please estimate the distance (feet or metres) from the grass level of this park (or the road level on US1), to the water level in the lake.
5. At GZ, please study the limestone there. If you poured water onto this rock, do you believe that it will run off quickly, or just get absorbed into the rock?
6. Bonus, tough question (you can get it wrong, but we hope you try to figure it out). It’s related to dissolved oxygen, fish, and the decay of organic matter. What do you think the purpose of the fountain is?
Optional:
Photos are optional, but they are always welcomed.
| MnS has earned GSA's highest level: |
 |
Additional Hints
(No hints available.)
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures