The Boring Lava Field (also known as the Boring Volcanic Field) is a Plio-Pleistocene volcanic field with cinder cones, small shield volcanoes, and lava flows in the northern Willamette Valley of the U.S. state of Oregon and adjacent southwest Washington state. The field got its name from the town of Boring, Oregon, located southeast of downtown Portland. Boring lies southeast of the most dense cluster of lava vents. The zone became volcanically active about 2.7 million years ago, with long periods of eruptive activity interspersed with quiescence. Its last eruptions took place about 57,000 years ago at the Beacon Rock cinder cone volcano; the individual volcanic vents of the field are considered extinct, but the field itself is not. The volcanic field covers an area of about , and it has a total volume of . This region sustains diverse flora and fauna within its habitat areas, which are subject to Portland's moderate climate with variable temperatures and mild precipitation. The highest elevation of the field is at Larch Mountain, which reaches a height of . The Portland metropolitan area, including suburbs, is one of the few places in the continental United States to have extinct volcanoes within a city's limits, and the Boring Lava Field plays an important role in local affairs, including the development of the Robertson Tunnel, recreation, and nature parks. Because of the field's proximity to densely populated areas, eruptive activity would be a threat to human life and property, but the probability for future eruptions affecting the Portland–Vancouver metropolitan area is very low. Boring Lava may also influence future earthquakes in the area, as intrusive rock from its historic eruptions may affect ground movement. Geography The Boring Lava deposits received their name based on their proximity to the town of Boring, which lies southeast of downtown Portland. The term "Boring Lava" is often used to refer to the local deposits erupted by vents in the field. They are located in the western portion of Oregon. The deposits were given this name by R. Treasher in 1942. In 2002, as geochemical and geochronological information on the Boring deposits accumulated, they were designated part of the larger Boring Lava Field. This grouping is somewhat informal and is based on similarities in age and lithology. The Boring Lava deposits lie west of the town of Boring. The Global Volcanism Program lists the volcanic field's highest elevation as ,