"Alright, Junior Geologists!" Ranger Ben called out. "Are you ready for another special part of our park? We're going to visit the bubbling mud pools!"
Mud pools? The children looked at each other with wide eyes. "Like a giant's bath?" Leo giggled.
They walked a little further, and soon they heard it: a soft, gurgling sound, like a tummy rumbling after a very big meal. And then they saw them!
Round, muddy puddles of gray, gooey mud bubbled and plopped. It looked like thick chocolate pudding, only it was mud, and it was warm!
"Whoa!" said Jill, carefully stepping closer to the fence that kept them safe. "It's like the ground is making soup!"
"That's exactly right, Jill!" Ranger Ben agreed. "This hot mud is a sign of geothermal activity. Geo means 'Earth,' and thermal means 'heat.' So, it's Earth's heat at work!"
Suddenly, with a soft 'WHOOSH!', a big puff of steam burst from a crack nearby, soaring up into the sky for just a moment before vanishing.
Everyone gasped! "It's alive!" Leo exclaimed, pointing.
"That's a geothermal vent," Ranger Ben explained. "It's like a little chimney for the steam to escape from deep underground."
A few scientists in special vests were working nearby. They had long sticks with thermometers on the end. One of them dipped a stick into a mud pool.
"They're measuring the temperature," Ranger Ben explained. "They want to know just how hot the Earth is right under our feet."