animation tree

Geology of a tree?
When a topic gets away

Have you ever started on a topic …

Only to get distracted on a different path?

Brought to you by Firelight Radio

I started off trying to talk about geology, but the next thing I knew I was rambling on about a tree. But not just any tree! And that’s when it suddenly dawned on me: cypress trees first took root in south Florida in the footprint of the Lake Okeechobee some six thousand years ago. None of those trees are still living today, but there is one special cypress tree on the outskirts of Lake Okeechobee that may very well be the most famous tree of all. The only problem: it got stuck on the wrong side of the levee. In this podcast, I explore the options for connecting the “lone cypress” with the larger ecosystem. And BTW: the Firelight Radio podcast is hosted by a guitar, i.e. you can’t have a nature-folk movement without a guitar by a campfire … that’s just obvious.

birds eye view

Origin of domes
And how geology controls the show

What came first:

The depression or the dome?

Answer: Cypress domes form in shallow surficial depressions in the swamp’s underlying caprock, but that doesn’t explain why some depressions capped by a cypress dome and others, right next door, form a tree-free herbaceous marsh.

It might have something to do with the thickness of the marl.

Cypress dome and circular marsh

Or maybe fire frequency or flooding depth also factors in.

Mark it down as another mystery of the swamp.

Cap rock walker
Watch you step!

As dangerous as it may look,

Walking on cap rock has its pleasures.

Watch out for the solution holes!

For the most part, the marine limestone that underlies the swamp is covered by a thin layer of marl and peat, except along this trail …

Where those soils eroded away.

At times it had a vertiginous feel …

Knowing there was three miles of limestone below.

Walking on the aquifer on a path to the clouds

And also a cavernous effect …

Being surrounded by skyscrapers of clouds on all sides.

There’s nothing quite like a wet walk in the swamp.

Caprock, marl and peat

A marine limestone called the Tamiami Formation underlies the Preserve to a depth of 150 ft (Hoffmeister 1974).  At its top surface, the rock formation forms a hard 1-2 ft thick crust called cap rock that functions as the bedrock for the Preserve ecosystem.  The cap rock is irregular, pocked with solution holes, and less permeable to water flow than the underlying rock formation (Duever et al 1979).  Although it can be exposed as a craggy pinnacle rock at the surface, cap rock is more typically covered with a thin layer of sand, marl or peat soils.  Cap rock and overlying soils form a semi-permeable seal that inhibits, but does not eliminate, ground and surface water exchange.  This semi-permeable seal augmented sheet flow and the formation of ground water fed springs in the pre-drainage Everglades (McCally, 1999).  Disruption of the caprock seal has occurred as a result of excavation of canals and borrow ponds. 

Duever, MJ, JE Carlson, JF Meeder, LC Duever, LH Gunderson, LA Riopelle, TR Alexander, RL Myers and DP Spangler.  The Big Cypress National Preserve.  Research Report No. 8 of the National Audubon Society, New York New York, 1979

McCally, David, The Everglades: An Environmental History, University Press of Florida, 1999

geology on wheels

More than just a Rock
Introducing Rock E

I get it, I really do:

When it comes to sight seeing – wading birds, alligators and flowers come first to mind.

As seen on Fire Light Radio

But where would any of those be without me, the geology? And I’m not saying you have to forgetthat other stuff. All I’m saying is it wouldn’t hurt to pay me some attention from time to time.

Us Rocks are more charismatic than you think …

And sort of the foundation of it all.

Slanted swamp?

The swamp may look flat …

To the human eye.

Not this slanted

But it’s actually slightly slanted.

About a half foot for every mile you move away from the coast.

The swamp is also bumpy, too:

Cypress mark its valleys and pinelands and hammocks its mountain tops.

A flat Big Cypress?

Only to the human eye.

Dinosaur swamp

Visitors are often struck … 

By its primordial aura of the Big Cypress Swamp.

As fanciful as that sounds,
it’s not too far from the truth.

I almost resembles a place that dinosaurs still lurk.