How a rare bog in Pennsylvania formed 13,000 years ago
The Tannersville Cranberry Bog began forming thousands of years ago.
“If we're standing here 13,000 years ago, best estimate by scientists, we're standing on top of a big huge bed rock slab," said Roger Spotts. "No trees in sight ... big lake down below us with icebergs or ice floating around in it. And maybe mastodons and woolly mammoths and saber-toothed cats walking by."
Spotts is the environmental education coordinator for the Monroe County Conservation District. During Bog Day on Sunday, Oct. 22, he lead a group through the national natural landmark in Monroe County.
The Tannersville Cranberry Bog is a relic of the ice age. It’s one of only two natural formations like it in Pennsylvania. The wetland formed after a glacier moved south from Canada. Over thousands of years, the thawing glacier created the big bowl, called a glacier kettle hole. The bog itself is only about 150 acres.
Once a glacier lake, it took thousands of years for the area to become a bog.
"The water into a bog is always precipitation, the water out is evaporation, there's no stream flowing into the bog, there's no stream flowing out of the bog," said Spotts.
The glacier picked up plants as it moved south. As it began to thaw, their seeds dropped. Sphagnum moss was first to grow.
For thousands of years, dead vegetation has sunk below the bog’s living layer. The center of the bog is 60 feet deep. Because it’s covered by water organic matter doesn’t decompose. The dead plants create acidity.
"The water in the summertime might be like on a pH scale like 3.5, which is almost vinegar level," said Spotts. "Only certain plants can tolerate that.”
Spotts pointed out cotton grass blowing in the wind. High bush blueberries fruit in the summer alongside rose hips. Larches, black spruce and red maple trees grow in the bog.
"The black spruce are really cool for a lot of reasons," he said. "But research tells us they grow about one foot every 10 years ... a 10-foot black spruce tree in the bog is 100 years old.”
Spotts said pitcher plants are the marquee plant of the bog. The carnivorous plant looks like a clump of green leaves with red lines growing out of the sphagnum moss.
“So a pitcher plant is only found in bogs," said Spotts. "Very rare in Pennsylvania."
They catch bugs without moving. The plants give off a smell that humans can’t detect and glow in a way that only insects can see.
The plant does produce some of its own food through photosynthesis but depends on bugs to supplement its diet, said Spotts.
Raymond Milewski, chair of the management committee for the Tannersville Cranberry Bog Preserve, has been involved in a research project at the bog over the last 14 years. They’re cutting back some denser plants to reestablish habitats for some rare plants. And it’s working.
"Orchids that haven't been seen since the 1950s, now are reappearing and blooming," said Milewski, a botanist.
Animals also enjoy the bog.
Bobcats walk along the boardwalk; they don’t like to get their feet wet, said Spotts. Trail cameras have also picked up coyotes and bears.
The large mammals like the super tart cranberries that sprout on little vines closer to the surface of the bog.
“When the bear comes in, he'll flatten this whole area," said Spotts. "He'll just lay down and slip along."
William Nearing, a Northeast Pennsylvania native and botanist, was one of the first people to study the bog. After a series of floods in the mid-20th century, he helped the Nature Conservancy purchase the bog in 1957.
"It was seen as this great natural resource because ... it basically acts like a sponge," said Stephen Ruswick, land steward and fire specialist at The Nature Conservancy in Pennsylvania and Delaware.
There's beaver dams and the sphagnum moss, which can hold 14 times it's own weight in water, he said.
"So that all kind of makes the water move a lot slower through that area," said Ruswick.
Towards the end of the guided walk on Sunday, Spotts picked up a small patch of the moss. When he squeezed it water came pouring out.
The Nature Conservancy has preserved over 1,000 acres of land around the bog.
Because of its fragile nature, the bog is not open to the public. The Monroe County Conservation District's Kettle Creek Environmental Education Center offers guided walks every Wednesday from May to November and usually once or twice a month on a weekend.
For more details, visit here.
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