The Yacolt 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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3.59 inches of rain fell in two days, the most for this week of the year since records began in 1928. The next wettest, 3.45 inches, fell in 1946.
Yacolt’s center stands about 710 ft above sea level. Within three miles the land runs from 510 ft to 1,720 ft, a difference of 1,210 ft: steep hill country. The highest named summit within 15 miles is Green Lookout Mountain, about 4,400 ft, 14 miles east.
Under the town center the state geologic map shows Quaternary nonmarine deposits (sandstone, clay, volcanic), from the Pleistocene, less than 2.6 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. 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, basaltic-andesite. Age: Late Eocene to Oligocene, 23 to 38 million years old. About 20 mi of the line.
Sandstone, clay, volcanic. Age: Pleistocene, less than 2.6 million years old. About 3 mi of the line.
Andesite. Age: Oligocene to Middle Miocene, 12 to 34 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.
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 Yacolt reaches the Pacific Ocean by way of Yacolt Creek, the East Fork Lewis, the Lewis and the Columbia: about 110 river miles.
85 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Yacolt; river miles along the main stem, rounded.
Yacolt has a warm-summer Mediterranean climate. Summer afternoons average 80° in August; winter nights fall to about 32° in January. About 52 inches of rain fall in a normal year, with about 1 inch of snow.
On November 14 Yacolt normally reaches 52° and falls to 36°. The record high is 71°, in 1995; the record low 9°, in 1955. The most rain on this date, 1.77 in, fell in 1942.
Normals 1991–2020 and records since 1928 at Battle Ground, 9 miles southwest, 430 ft lower. NOAA, through RCC-ACIS.
