The Tualatin 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.
Tualatin’s center stands about 130 ft above sea level. Within three miles the land runs from 110 ft to 490 ft, a difference of 380 ft: rolling country. The highest named summit within 15 miles is Bald Peak, about 1,650 ft, 14 miles west.
Under the town center the state geologic map shows Alluvial deposits (sand, gravel, silt), from the Holocene, less than 12,000 years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 18×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Basalt. Age: Miocene, 5.3 to 23 million years old. About 12 mi of the line.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 9 mi of the line.
Silt, sand, gravel. Age: Pleistocene, less than 2.6 million years old. About 1 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 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.
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 Tualatin reaches the Pacific Ocean by way of Hedges Creek, the Tualatin, the Willamette and the Columbia: about 140 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 Tualatin; river miles along the main stem, rounded.
Tualatin 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 Tualatin 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, 10 miles north-northeast). NOAA, through RCC-ACIS.
