The West Haven-Sylvan plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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71° on Nov. 13, 1999, the hottest reading for this week of the year since 1872. Next is 68° in 1976.
West Haven-Sylvan’s center stands about 610 ft above sea level. Within three miles the land runs from 150 ft to 1,130 ft, a difference of 980 ft: steep hill country. The highest named summit within 15 miles is Dixie Mountain, about 1,620 ft, 15 miles north-northwest.
Under the town center the state geologic map shows Sedimentary rocks (sandstone-mudstone), from the Pliocene to Pleistocene, less than 5.3 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 15×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Sandstone-mudstone. Age: Pliocene to Pleistocene, less than 5.3 million years old. About 4 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 4 mi of the line.
Basalt. Age: Miocene, 5.3 to 23 million years old. About 4 mi of the line.
Sandstone, clay, volcanic. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Silt, sand, gravel. Age: Pleistocene, less than 2.6 million years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 2 smaller units along the line are not listed.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in West Haven-Sylvan reaches the Pacific Ocean by way of Johnson Creek, Cedar Mill Creek, Beaverton Creek, Rock Creek, the Tualatin, the Willamette and the Columbia: about 180 river miles.
Lake on the way: Willamette Falls Hydroelectric Power Reservoir.
100 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of West Haven-Sylvan; river miles along the main stem, rounded.
West Haven-Sylvan has a warm-summer Mediterranean climate. Summer afternoons average 81° in August; winter nights fall to about 37° in January. About 44 inches of rain fall in a normal year, with about 4 inches of snow.
On November 14 West Haven-Sylvan normally reaches 53° and falls to 42°. The record high is 66°, in 2001; the record low 18°, in 1955. The most rain on this date, 2.18 in, fell in 1876.
Normals 1991–2020 and records since 1872 from the Portland Downtown Area threaded record (Portland Kgw-Tv, 4 miles east, 450 ft lower). NOAA, through RCC-ACIS.
