1. SINKHOLE FORMATION Lake Jackson Florida, US
Katie Reynolds and Anjuli Jackson

2. Karst Topography H2O + CO2 → H2CO3 Formed in limestone, dolomite
Shaped by dissolution of layers of soluble carbonate bed rock
Mildly acidic water:
H2O + CO2 → H2CO3
Soaks up water like a sponge
Little remaining surface water
Characterised by:
Sinkholes
Caves
Underground drainage systems
20% of Earth’s dry land surface is Karst

3. Karst scenery, China

4. SINKHOLES in Florida
Almost 75% of continental US has the right geology for sinkholes
Floridian Geology
Limestone
Sinkholes
Three general forms occur in Florida
Collapse
Solution
Subsidence
LAKE JACKSON
Lake Jackson

5. Lake Formation Dissolution of uppermost soluble rock
Fresh water percolates through fractures
Drain water and rain water focussed in depression
Debris plugs outflow to form lake
Stage 3
Stage 1
Stage 2

6. LAKE JACKSON
Two active sinkholes in the bottom of the lake are remnant features of these karst processes –
Lime Sink in the northern portion
Porter Hole Sink in the southern area.

7. LAKE JACKSON The lake is in a closed 27,000-acre drainage basin.
Water flows into the lake constantly
Water can only leave through evaporation or leakage through sinkholes in the bottom of the lake.
Sinkholes open and drain portions of the lake approx. every 25 years since 1800s
Low Water Table
Low Rainfall/Drought Conditions
September 1999 Lake Jackson and all its inhabitants drained down 8ft diameter sinkhole within a few short days

8. Aerial Photo of Lake Jackson Sinkhole, 1999
“It was spectacular” said Jess Van Dyke, a regional biologist for the State of Florida who was on the scene when it happened. He saw “animals trying to scramble out, a whirlpool or gators, birds and bass went down the hole.”

9. Sediment being scraped off bottom of lake bed by earthmoving equipment
Issues
Lake drains into Floridian Aquifer, a source of drinking water
Pollution contained in stormwater runoff enters lake
Interstate-10
Urban/Suburban development
sediment
fertiliser
Oil
Gasoline
Sediment being scraped off bottom of lake bed by earthmoving equipment
Treat runoff before it enters lake
5 stormwater treatment facilities
Removal of sediment from bottom of lake during natural drydown
More cost effective than hydraulic dredging
Solutions

10. Lake Jackson Since 1999 Lake slowly refilled due to:
regular, wet weather patterns
Inflow exceeding drainage
In 1957 attempts were made to plug the Lime sink with debris with little success
Today:
Lake managers believe the natural cycle is best