In the 1974 Mount Edgecumbe eruption prank, 70 tires were ignited.
On April 1, 1974, Oliver “Porky” Bickar and collaborators staged the apparent eruption of Mount Edgecumbe near Sitka, Alaska. They used a helicopter to place old tires and other combustible materials in the crater of the long-dormant volcano, then set them alight to create thick black smoke.
The spectacle alarmed people in Sitka, who could see smoke rising from the mountain. The pranksters had also marked the snow with “APRIL FOOL,” revealing the joke after the scene had attracted attention. Mount Edgecumbe had not erupted; the smoke came from the deliberately burned tires.
The number is often confused with rounded retellings such as “nearly 100 tires,” but the commonly documented figure is 70. The prank is also sometimes mistakenly dated to 1972; the famous staged eruption occurred on April 1, 1974.