Sinkholes: Its the Geology stupid!

#Florida

So after I wrote my blog I was wondering if we get sinkholes here in Martin County. Will my house get get sucked up in a hole. Will I be calling 911 saying “I’m in the ground!” Yikes.

I live on a ancient sand dune by the Indian RIver Lagoon. I live on a hill. I expect my house will be water view in about 50 years if we don’t do anything about sea level rise. I picked this area besides being so close to the lagoon, it was on a hill and out of the flood zone.

So much for planning.

The sinkholes of Martin County.

http://www.insurancejournal.com/news/southeast/2011/03/30/192278.htm

RiskMeter’s Top 10 Sinkhole-Prone Counties in Florida are:

Pasco
Hernando
Hillsborough
Marion
Pinellas
Citrus
Polk
Orange
Seminole
Lake

Geology

https://en.wikipedia.org/wiki/Geology_of_Florida

During the early Mesozoic Era (251 – 66 mya) the supercontinent of Pangea began to rift and break apart. As North America separated from Africa a small portion of the African plate detached and was carried away with the North American plate. This provided some of the foundation upon which Florida now rests.

(I love this. Pretty cool if you think about it.)

The Florida peninsula is a porous plateau of karst limestone sitting atop bedrock known as the Florida Platform. The emergent portion of the platform was created during the Eocene to Oligocene as the Gulf Trough filled with silts, clays, and sands. Flora and fauna began appearing during the Miocene. No land animals were present in Florida prior to the Miocene.

The largest deposits of rock phosphate in the country are found in Florida. Most of this is in Bone Valley.

Extended systems of underwater caves, sinkholes and springs are found throughout the state and supply most of the water used by residents. The limestone is topped with sandy soils deposited as ancient beaches over millions of years as global sea levels rose and fell. During the last glacial period, lower sea levels and a drier climate revealed a much wider peninsula, largely savanna.

Science

Really incredible explanation on connection between farming and sinkholes and how the aquifers are pumped out and how cavities are left over and then they collapse.

He brings us up a lot of good points.

http://dep.state.fl.us/geology/geologictopics/hazards/sinkholes.htm

“Sinkholes become more of a problem in areas where sediments that lie above the limestone are mainly clays mixed with sand. Clay causes these sediments, which also range in thickness from 30 to 200 feet, to be cohesive. They are not very permeable to water. In these areas sinkholes are most numerous. They vary in size and may form suddenly. In a few areas of Florida over 200 feet of sediments cover the underlying limestone. These sediments are cohesive because of the clay and layers of limestone they contain. Although there are not many sinkholes in these areas, the ones that occur are deep and wide. These types of sinkholes are referred to as “cover-collapse sinkholes” because cohesive layers of sediment collapse into underground cavities when they form.”

Do we really need to be messing around in the land underneath us?

Do we need to look for oil? DO we need to suck the water out of the earth? Why are we messing with Mother Nature? Do we need to frack?

no. no. no.

We need to find betters ways to preserve or we’ll be the ones sucked down and yelling “I’m the ground!”

Here is a lesson. I’m not sure what grade it’s for but if your 6th graders can understand this stuff perhaps our legislators can.

http://teachingboxes.org/seaLevel/lessons/lesson4_reefs/index.htm

Coral reefs only grow in shallow, clear sea water (in the photic zone).

Reefs and Sea Level

When sea level is stationary, reefs will grow laterally in a seaward direction as reef sediments accumulate. Over long periods of time reef sediments will accumulate, and the growing pile will buid up in a seaward direction. Over time, this reef material will build broad shoals and platforms just below and near the ocean’s surface. However, if sea level rises and reefs are submerged by deep water, tehy will die. The deep water isolates them form the necessary solar light and warm water conditions they require. Similarly, a drop in sea level could leve them exposed on land.

Image source: U.S. Geological Survey (http://geopubs.wr.usgs.gov/fact-sheet/fs025-02

There’s even an extra brain teaser on the bottom!

Extra Brain Teaser: read about Florida’s sinkholes and what they tell of about sea level in the past!

Man I love Science!

http://www.newsweek.com/2014/02/28/oil-prospectors-seek-their-next-big-strike-south-floridas-everglades-245596.html

“The letter was printed on plain white paper in plain black type, and but for its unfamiliar globe logo “Total Safety” and its unsettling message, it was no different from most of the junk mail filling the mailboxes of 30 homes in a rural south Florida area called Golden Gate Estates, east of Naples.

“Dear Sir or Madam,” it read, “Total Safety US, Inc. is currently going around your area gathering information on households for Dan A. Hughes, so we can develop a contingency plan. We need the name of the main contact of the household, the number of people in your household, address and a number where you could be contacted in case of emergency, if you have transportation to evacuate and if you have any special needs in transportation.

With a little research, one of the many perplexed recipients, a retired artist by the name of Jaime Duran, learned that Dan A. Hughes was a Beeville, Texas-based oil outfit and that the company planned on drilling a test well on the pasture alongside his log cabin, less than 1,000 feet from his front porch.

The geological traits that make Florida good for oil exploration might also make it particularly environmentally risky. Andrew Zimmerman, an associate professor in the University of Florida’s geology department, tells Newsweek that the state’s oil is found in cracked, porous limestone formations. This is also the same rock sourcing drinking water. Plus, south Florida already has its share of water problems. In addition to water managers constantly balancing over-wet or over-dry conditions, they are often being caught between the two bad choices of over-drawing from aquifers or dumping fresh water into the ocean. Lake Okeechobee, which is also a major player in the region’s water sources, is another ongoing problem, as the U.S. Army Corps of Engineers has recently diverted polluted water into the St. Lucie and Caloosahatchee Rivers from the lake to prevent its 80-year-old dike from bursting. That has dealt a near deathblow to these rivers’ estuaries, with locals complaining that the lake’s waters containing agricultural chemicals from nearby farms have killed numerous manatees, dolphins, fish and oysters.”

In a worst-case scenario, drilling could have deadly consequences.

Hydrogen sulfide is a gas that smells of eggs but rivals hydrogen cyanide in its potential to kill and is often present in fields with sour crude oil, the kind found in south Florida.