(water rumbling) - You're at Cherney Maribel Caves County Park in Northern Manitowoc County.

And this is the Spring Cave, right at the boundary of the park.

And the spring cave is part of the Maribel New Hope Cave System.

And it's believed to drain an area of approximately six square miles to the west of here.

This is the West Twin River.

And if you were to go up a little further, the Devils River that comes past the Devils River Campground intersects this and continues flowing towards Two Rivers.

(water rustling) What's neat about a cave is tomorrow you could suddenly find a cave right underneath your property and not even know it existed.

(shovel clanging) (water rustling) (dirt thudding) - There's different ways you can find caves.

There's very expensive ways of doing it, which is like penetrating radar or resistivity testing, both of which shoot electrical currents underground.

Unfortunately, penetrating radar doesn't work very well in Wisconsin 'cause we have too much clay in the soil.

It can only see like about 10 feet under ground.

And the cave that we're in here now is the same temperature as it is in the middle of the winter.

Temperature doesn't vary that much.

And so whatever the mean annual temperature where the cave is located is the temperature in the cave.

In Wisconsin it's between 42 and 48 degrees.

You know, the further north you get, the colder the caves get, okay.

So keeping that in mind, the temperature of the cave stays the same.

So what you want to do is go when it's really, really cold outside, and then you look for what is the cave's breathe, and they actually breathe out warm air.

(shovel scraping) (water rustling) (shovel scraping) Wherever you see a crisscross of cave lifelines, that's a good indication that you have a side passage.

And lifelines are important because that's how a cave forms.

Those lifelines are a crack which go all the way to the surface.

So when it rains outside, rainwater is gonna combine with the carbon dioxide that's either in the air or in the leaf letter.

You combine those two and you get carbonic acid.

So that carbonic acid leaches into this softer rock, which is a type of limestone, and it's actually started pitting it.

It started making holes.

Then you start having any kind of flowing water going through that hole.

Anything that's abrasive in the water, such as sand and gravel, will actually start making that passage bigger.

(water rustling)