The Mehama 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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70° on Nov. 14, 1999, the hottest reading for this week of the year since 1951. Next is 68° in 1976.
Mehama’s center stands about 620 ft above sea level. Within three miles the land runs from 560 ft to 2,190 ft, a difference of 1,630 ft: steep hill country. The highest named summit within 15 miles is Mount Horeb, about 4,510 ft, 14 miles east.
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 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 6×. 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 9 mi of the line.
Basalt, andesite, basaltic-andesite. Age: Early Miocene to Late Miocene, 10 to 17 million years old. About 6 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 3 mi of the line.
Basalt, basaltic-andesite. Age: Oligocene to Miocene, 5.3 to 34 million years old. About 3 mi of the line.
Volcanic, conglomerate, andesite. Age: Miocene, 5.3 to 23 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 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 Mehama reaches the Pacific Ocean by way of Stout Creek, the North Santiam, the Santiam, the Willamette and the Columbia: about 240 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 Mehama; river miles along the main stem, rounded.
Mehama has a warm-summer Mediterranean climate. Summer afternoons average 81° in July; winter nights fall to about 34° in January. About 53 inches of rain fall in a normal year.
On November 14 Mehama normally reaches 52° and falls to 39°. The record high is 70°, in 1999; the record low 14°, in 1955. The most rain on this date, 1.62 in, fell in 1966.
Normals 1991–2020 and records since 1951 at Stayton, 9 miles west, 200 ft lower. NOAA, through RCC-ACIS.
