Florida’s Ice Age, Ice Cores Tell the Story


Saturday afternoon, July 27, was a gorgeous summer day. Despite temperatures in the low 90s and typical Southwest Florida humidity, there was hardly a cloud in the sky, much less thunderstorms. So many people packed Fort Myers Beach that traffic crossing the Matanzas Pass Bridge went all the way back to Buttonwood Drive, making one briefly wonder if this were January rather than July. Nothing screamed indoor educational program!

Yet the historic Mound House somehow beat all the odds by presenting “Florida’s Ice Age” at 2 p.m., with Rachael Kangas, the Public Archaeology Coordinator for the Florida Public Archaeology Network’s Southwest Region, with roughly 20 people in attendance! For those who sacrificed their fun in the sun, Kangas offered a fun, educational and entertaining program in a highly enthusiastic manner.

Fossils Vs. Artifacts

“The worst part of my job is I ruin the lives of the kids in the audience by saying I do not talk about dinosaurs,” began Kangas with a huge smile! “Paleontologists study things like dinosaur bones and teeth, while archaeologists examine artifacts, and that is the difference – fossils versus artifacts. Fossils are evidence of living things preserved in the Earth’s crust, while artifacts are items made or modified by humans, so archaeology is all about artifacts.”

Florida has been around much longer than any peoples who lived here, Rachael explained. “Around 125 million years ago, Florida was not even close to being on the globe where we are right now, but was part of the supercontinent of Pangea, sandwiched between North and South America and Africa, before everything broke up and shifted around. Up to 65 million years ago, while dinosaurs were hanging around other parts of North America, Florida was under the ocean, so that is why we do not find any evidence of T. Rex here! Sea creatures died and sank, becoming carbonite material that stacked up over millions of years to became limestone, so that is why Florida today in little more than sand and water and millions of built-up layers of limestone.”

She discussed Florida’s most recent high and low water marks: “The highest water was 125,000 years ago, when global temperatures were really hot and the ice caps melted, creating oceans so high, Florida was mostly underwater. Over time, temperatures began to cool, with ice caps reforming and oceans lowering. Eventually, little bits of land began to stick out of the water until we reached the last Great Ice Age 10,000 years ago, with thick ice caps and low oceans. It is this Great Ice Age that really excites me, as Florida emerged out of the Gulf of Mexico, with the sea level roughly 100 feet lower than it is now and Florida roughly twice the land mass it is today, leading to a very different environment that we call the Paleoindian Period, corresponding with the first appearance of humans in the North American archaeological record.”

“We study these environmental changes through ice cores that contain frozen bubbles full of atmosphere and this is the coolest thing in the world!” Rachael stated. “These ice cores tell us that carbon dioxide levels have gone up and down over the past 800,000 years, to correspond to how hot and cold the Earth is, with our current levels the highest ever by far over that timeframe, and that is what everyone is freaking out all about.”

As a result of the Great Ice Age, Florida then looked much different than now, Rachael noted. “Florida was much more like a savannah, with a cooler and drier climate; nothing at all like the hot and humid and sticky place that we call home. Megafauna animals roamed the area, and these were huge, like the giant land sloths that were up to 19 feet long, along with mastodons and mammoths that were living happy lives and grew so large from eating all of the savannah grasses. We get all of these answers through archaeology.”

Nice Happy Florida Lives

With water levels again rising, much of this history is currently trapped underwater, leaving archaeologists like Rachael to do much of their work in scuba gear! “We use vacuums with big hoses that pump the material up to boats on the surface where we catch all the material is a series of screens, with the smallest the size of those found in your home windows. This is obviously not the easiest thing to do but very fun, especially when you get an animal bone with an arrow tip in it, as that is ‘The Smoking Gun’ about animal interaction with human beings and excellent finds. Two of the main Florida spots are Little Salt Springs and the Aucilla River Site that is 4,000 years older than any other area we have yet to discover, making it an archaeologist’s dream and just so cool!”

The Paleoindian Period began to end about 6,000 years ago “because warming caused the ice caps to melt and seas to rise to present levels,” Rachael related, “leading to the formation of The Everglades. The Megafauna went extinct, but we humans are smart and quickly adapted to live our nice happy lives in Florida.”

The Mound House, at 451 Connecticut Street, is the oldest standing structure on Estero Island, with overflow parking at 216 Connecticut. The Town of Fort Myers Beach now operates the Mound House as a museum complex that offers numerous educational programs each month, including guided tours to explore the 2,000-year-old Calusa Indian Shell Mound, beach walks, and kayak eco-tours. Admission is $10 for ages 13 & up, $8 for students with IDs, $5 ages 6 to 12, and 5 & under free, with Town residents receiving a 50% discount. Save 20% on kayak tours for a limited time with the registration code, SUMMER20, and half off Mound House admission when you mention MOUNDHOUSE2019. It is open Tuesdays, Wednesdays & Saturdays from 9 a.m. to 4 p.m. For information and programs, call 239-765-0865 or visit www.moundhouse.org.


By Gary Mooney