The Idanha 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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74° on Nov. 15, 1995, the hottest reading for this week of the year since 1954. Next is 70° in 1974.
Idanha’s center stands about 1,710 ft above sea level. Within three miles the land runs from 1,600 ft to 3,820 ft, a difference of 2,220 ft: mountain country. The highest named summit within 15 miles is Mount Jefferson, about 10,280 ft, 14 miles east.
Under the town center the state geologic map shows Undifferentiated tuffaceous sedimentary rocks, tuffs, and basalt (basalt, basaltic-andesite), from the Oligocene to Miocene, 5.3 to 34 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 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: Oligocene to Miocene, 5.3 to 34 million years old. About 11 mi of the line.
Basalt, andesite, basaltic-andesite. Age: Early Miocene to Late Miocene, 10 to 17 million years old. About 5 mi of the line.
Basaltic-andesite, basalt. Age: Early Pliocene to Pleistocene, 1.2 to 3.9 million years old. About 4 mi of the line.
Gravel, sand, boulders. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Basalt, basaltic-andesite. Age: Oligocene to Miocene, 5.3 to 34 million years old. About 1 mi of the line.
Basaltic-andesite, andesite. Age: Pliocene to Pleistocene, less than 5.3 million years old. About 0.9 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 Idanha reaches the Pacific Ocean by way of the North Santiam, the Santiam, the Willamette and the Columbia: about 280 river miles.
Lakes on the way: Willamette Falls Hydroelectric Power Reservoir and Detroit Lake.
100 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Idanha; river miles along the main stem, rounded.
Idanha has a warm-summer Mediterranean climate. Summer afternoons average 81° in August; winter nights fall to about 36° in January. A normal year brings about 10 inches of snow; with the rain, that comes to about 94 inches of water.
On November 14 Idanha normally reaches 50° and falls to 41°. The record high is 62°, in 1974; the record low 21°, in 1955. The most rain on this date, 3.00 in, fell in 1966.
Normals 1991–2020 and records since 1954 at Detroit Dam, 9 miles west, 490 ft lower. NOAA, through RCC-ACIS.
