With 401 units of the National Park System, how do you decide what to do during National Park Week? The folks at the National Park Service and National Park Foundation have some suggestions for you.

Timing often is happenstance, but with Earth Day arriving next week, word of high mercury levels in fish in national parks from Alaska to Colorado is particularly sobering. In some cases, the levels exceed limits OKed for human consumption.

Nearly a century ago, the dramatic landscape now included in Craters of the Moon National Monument was virtually unknown to all but a few hardy adventurers. One of them, Robert Limbert, hiked across the area in 1920, and his photos and articles are credited with spurring creation of the Monument in 1924. This week, a small group of hikers is recreating Limbert's historic trek, and sharing their progress via social media.

Rivers run fast and tumbling throughout the National Park System, there are streams with lazy meanders, and placid lakes perfect for dipping a paddle. This diversity poses a delightful dilemma when you have the urge to float and paddle. What follows is just a sampling of the experiences that await you, whether you have hundreds of watery miles under your paddle, or are looking for calm waters to take your youngsters