When you think of a lake bed, what comes to mind? Squishy bottom with some grasses, rocks, and sunken logs? The floor of Yellowstone Lake has hot springs, sinter deposits, altered muds, heat-loving bacteria, rocky siliceous spires, and hydrothermal explosion craters. These features have been the subject of intense study over the last 20 years, and research results show that the springs have an impact on the chemistry of the lake itself.

With concerns growing that the federal government will shut down, at least partially, later this week, the question of whether the National Park System will be open to visitors is a natural one. The answer is yes, but with some caveats.

Hours spent in a line waiting to enter a national park. Crews working to maintain trails that climb through piny forests and are blighted by piles of human waste. Visitors taking out their rage against fellow visitors and park staff when they can't find a parking spot at their favorite trailhead or overlook. These are some of the issues National Park Service staff are trying to solve as they cope with record visitation.

Interior Secretary Ryan Zinke, a lightning rod for conservationists and environmentalists and long portrayed by his critics as being in the pocket of the energy industry, will leave the administration by year's end, President Trump said Saturday.