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

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Presentation on theme: "SINKHOLE FORMATION Lake Jackson Florida, US Katie Reynolds and Anjuli Jackson."— Presentation transcript:

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

2 Karst Topography  Formed in limestone, dolomite  Shaped by dissolution of layers of soluble carbonate bed rock  Mildly acidic water : H 2 O + CO 2 → H 2 CO 3  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  Formed in limestone, dolomite  Shaped by dissolution of layers of soluble carbonate bed rock  Mildly acidic water : H 2 O + CO 2 → H 2 CO 3  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  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 Stage 1Stage 2 Stage 3  Dissolution of uppermost soluble rock  Fresh water percolates through fractures  Drain water and rain water focussed in depression  Debris plugs outflow to form lake  Dissolution of uppermost soluble rock  Fresh water percolates through fractures  Drain water and rain water focussed in depression  Debris plugs outflow to form lake

6  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.  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. LAKE JACKSON

7  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  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 Issues Sediment being scraped off bottom of lake bed by earthmoving equipment  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  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  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  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  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


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