The Siletz 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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20° on Nov. 13, 1978, the coldest reading for this week of the year since 1893. Next is 21° in 1955.
Siletz’s center stands about 130 ft above sea level. Within three miles the land runs from 90 ft to 780 ft, a difference of 690 ft: hilly country. The highest named summit within 15 miles is Big Tip, about 2,810 ft, 12 miles northeast.
Under the town center the state geologic map shows Terrace, pediment, and lag gravels (gravel, boulders, clay), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 10×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone. Age: Middle Eocene, 38 to 48 million years old. About 7 mi of the line.
Sandstone, conglomerate, siltstone. Age: Late Oligocene to Early Miocene, 16 to 28 million years old. About 4 mi of the line.
Basalt. Age: Paleocene to Middle Eocene, 38 to 66 million years old. About 3 mi of the line.
Siltstone, sandstone. Age: Early Miocene to Middle Miocene, 12 to 23 million years old. About 2 mi of the line.
Gravel, boulders, clay. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 mi of the line.
Siltstone. Age: Middle Eocene to Late Eocene, 34 to 48 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. 3 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 Siletz reaches the Pacific Ocean by way of the Siletz: about 35 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Siletz; river miles along the main stem, rounded.
Siletz has a warm-summer Mediterranean climate. Summer afternoons average 64° in July; winter nights fall to about 39° in January. About 67 inches of rain fall in a normal year.
On November 14 Siletz normally reaches 54° and falls to 42°. The record high is 72°, in 1995; the record low 22°, in 1978. The most rain on this date, 2.00 in, fell in 1918.
Normals 1991–2020 and records since 1893 at Newport, 9 miles southwest. NOAA, through RCC-ACIS.
