the floor of former Lake Lewis in Eastern Washington. Allison is also known for his work in the 1930s documenting the hundreds of non-native boulders (called erratics) washed down by the floods, rafted on icebergs and deposited on the valley bottom and in a ring around the lower hills surrounding the Willamette Valley. One of the most prominent of these is the Bellevue Erratic, just off Oregon Route 18 west of McMinnville. It is also believed that the Willamette Meteorite was rafted by flood and ice to the location near West Linn where it was found in 1902. Geography The valley may be loosely defined as the broad plain of the Willamette, bounded on the west by the Oregon Coast Range and on the east by the Cascade Range. It is bounded on the south by the Calapooya Mountains, which separate the headwaters of the Willamette from the Umpqua River valley about south of Hidden Valley. Interstate 5 (I-5) runs the length of the valley, linking its major communities. Because of differing cultural and political interests, the Portland metropolitan area and Tualatin River valley are sometimes not included in the local use of the term, though both are located within the geographical valley. Additionally, the east slopes of the Coast Ranges and the west slopes of the Cascade Range from Oakridge to Detroit Lake can be considered part of the Willamette Valley in a cultural sense, despite being mountainous areas. Cities in the valley include, from south to north, Cottage Grove, Eugene and Springfield (the two cities form a single populated area, separated in places only by I-5 and/or the McKenzie River), Corvallis, Albany, Dallas, Salem, Keizer, McMinnville, and Hillsboro. Parts of the following counties, from south to north, lie within the valley: Douglas County, Lane County, Linn County, Benton County, Polk County, Marion County, Yamhill County, and Washington County. Sometimes the area around Albany and Corvallis and surrounding Benton and Linn counties is referred to locally as the Mid-Valley. Marion, Polk, and other counties are sometimes included in the definition of the Mid-Valley. Climate The climate of the Willamette Valley is a mix of Mediterranean (Köppen Csb) and oceanic (Köppen Cfb) influences. The Köppen climate classification system considers it Mediterranean, but compared to a true Mediterranean climate it is cooler and moister, with a longer rainy season. The main climatic features are moderate temperatures and frequent cloudiness and rains,