Native people knew Mount St. Helens by names meaning "Fire Mountain" or "Smoker" and watched it erupt repeatedly, building most of the visible mountain over the last 2,800 years. Eruptions and heavy ash fall caused them to abandon sites for centuries. Mount St. Helens is the youngest and most explosive of the Cascade volcanoes, and several eruptions were larger than that of 1980. Thirty-five hundred years ago it erupted and produced 13 times more pumice, ash, and rock than on May 18, 1980. By studying the mountain's volcanic deposits, geologists better understand its eruptive history and likely future, and it should continue intermittent eruptions for decades before resting. Around 3,500 years ago, an eruption deposited a deep layer of pumice and ash over the Koapk Site in about a day, and Native Americans abandoned the site, returning 2,000 years later before a final abandonment around 1860 A.D. At the Layser Cave Site, repeated eruptions deposited close to 15 inches of ash and pumice, and the inhabitants abandoned it permanently around 3,900 years ago. At the Boundary Trail Site, lighter colored ash accumulated over several hundred years, and the site was permanently abandoned between 3,500 and 3,900 years ago. The Lower Falls Site received at least 31 inches of ash and pumice over several hundred years; its inhabitants left around 3,900 years ago, it was reoccupied from 1880 to 1900 A.D., and finally abandoned in 1960. In 1847, artist Paul Kane painted a dome-building eruption on the mountain's north flank, and eruptions between 1842 and 1857 built the Goat Rocks lava dome.