Yellowstone National Park closed all entrances Monday as flooding and rock and mud slides chewed away at park roads, forcing the evacuation of visitors in northern areas of the park due to "extremely hazardous conditions." With the potential for severe flooding in the southern half of the park, officials made the decision to shutter the entire park. Dramatic aerial footage captured by the park's helicopter manager demonstrated the damage being inflicted on the park.

There’s always something to learn about the park units within the National Park System. Take this latest National Parks Traveler quiz and trivia piece and see just how much you really know, while maybe learning a little in the process.

One of the best hikes in Everglades National Park is a slough slog into a cypress dome. Ranger Yvette Cano, the park's education director, explains what such a hike is like, and then she and Frank Dean, president and CEO of the Yosemite Conservancy, explain the challenges of funding educational and interpretive programs in the parks. They often are not part of a park's government-funded budget.

Chicken eggs are pretty good chum, but alligator and crocodile eggs, sea turtle eggs, and even bird eggs are also high on the menu for black-and-white Argentine tegus, a lizard that arrived in Florida through the pet store trade and is threatening to upend Everglades National Park's ecosystems.