Complex sentence: Broader tensions in American society surfaced in Yosemite when a large number of youths gathered in the park over the summer of 1970, triggering a riot on July 4 after rangers tried to evict visitors from camping illegally in Stoneman Meadow.
Split into simpler sentences: Broader tensions in American society were felt in Yosemite in 1970, when a large number of youths gathered in the park over the summer. A riot was started by youths on July 4 after rangers tried to evict visitors from illegally camping in Stoneman Meadow.