This year is the 100th birthday of the National Park Service. Yellowstone National Park is the nationâ??s oldest, with its Old Faithful geyser and grizzly bears. Lucky Severson visited it recently and talked with sightseers about the beauty, peace andâ??for manyâ??the sense of the holy that they find there. He also talked with Yellowstoneâ??s Superintendent about the parkâ??s future, as it tries to cope with the effects of global warming on the geysers and concerns about the effects of the bigger and bigger crowds of visitors.