About 70 million years ago, the tectonic plates underlying the Pacific Ocean plunged beneath the North American Plate and began to form the row of volcanoes known as the Cascade Range. Lassen Volcanic National Park crowns the southernmost part of the range in a remote region of northeastern California. The Park is most famous for its spectacular geology, the result of active vulcanism from the ongoing creation of the Cascade Range. The vast majority of the Park’s rock formed within the past three million years as a series of volcanoes rose up and eroded away. Lassen Peak, the Park’s tallest mountain, formed about 27,000 years ago, near the end of the last Ice Age. The Peak hosted the Park’s most recent eruptions from 1914 to 1917. The Park also boasts 17 smaller volcanoes and four mountains remaining along the rim of an enormous eroded volcano. In nine hydrothermal areas, subterranean molten rock heats bodies of water at the Earth’s surface and enriches the soil with otherworldly yellows and reds. The steam and sulfuric stench reminds us that the Park’s history of eruptions is far from over.