The Portal: Groundhogs Lead Us Into an Underrealm of HOLES

Jan 29, 2026

They dig into real fossil quarries and unearth Cretaceous treasures. They explore underwater microbial mats that hint at ancient, faster days. They wander vast cave systems and meet eyeless subterranean creatures. They tell the wild story of a Corvette sinkhole and tour clever animal burrows from termite towers to a groundhog’s cozy grotto.

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INSIGHT

Layers Are A Geological Timeline

Each foot down in the quarry represents hundreds of thousands to millions of years of history in layered rock.
Reading those layers reveals dramatic shifts like oceans, megafauna, and mass extinctions.

ANECDOTE

Standing At The Extinction Layer

The crew dug to the extinction layer that marks the asteroid impact 66 million years ago.
They described ash, global fires, and burial of species in a thin dust band visible in many places on Earth.

INSIGHT

Holes Can Hold Stardust

Some soil layers contain high iridium from the asteroid, and other layers capture stardust from exploded stars.
Holes and sediments can literally trap extraterrestrial material for scientists to study.

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Holes are full of a whole lot of nothin'. Pure, hollow emptiness. At least that’s what Songbud Alan thought before he fell down a rabbit hole of, well, HOLES! In honor of Groundhog Day, he takes Lulu to a fossil-filled pit behind a Chick-fil-A to dig up 66-million-year-old treasure, and deep down to an underwater hole where blobs of colorful microbes reveal a time when Earth’s days were only 6 hours long. We discover eyeless cave fish, fall into a sinkhole of Corvettes, and go house hunting for the perfect animal hole to cozy up in... which leads us to one of the coziest holes of all: a groundhog’s burrow.

Want to DIG deeper?

Learn more about Staten Island Chuck, the groundhog with the highest spring prediction accuracy.
Explore Edelman Fossil Park and dig for real fossils.
Discover Mammoth Cave.
Check out eyeless cave fish.
Read about the Corvette Museum Sinkhole and how sinkholes form.

Terrestrials was created by Lulu Miller with WNYC. This episode was produced by Alan Goffinski, with sound design by Mira Burt-Wintonick. Sarah Sandbach is our Executive Producer. Our team also includes Ana González, Tanya Chawla and Joe Plourde. Factchecking by Sophie Samiee.

Support for Terrestrials is provided by the Simons Foundation, the Arthur Vining Davis Foundations, and the John Templeton Foundation.

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