On a hot, sunny day in California, I crawled into the tiny cockpit of a small Cessna aircraft to fly around one of the state’s most active volcanoes, Mt. Lassen. Video by Peter Berger I wasn’t looking for lava. The volcano in Lassen Volcanic National Park hasn’t erupted in more than 100 years. Instead, I was looking for the telltale signs of herbicide spraying across vast stretches of forestland. I’d already seen it from the ground: seemingly en…