The Alpharetta 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.
Sunny
Mostly sunny
Mostly sunny
Sunny
Sunny
Mostly sunny
Mostly sunny
Alpharetta’s center stands about 1,130 ft above sea level. Within three miles the land runs from 980 ft to 1,170 ft, a difference of 190 ft: gently rolling country. The highest named summit within 15 miles is Sawnee Mountain, about 1,940 ft, 13 miles northeast.
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 47×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Amphibolite, biotite-gneiss, mica-schist. Age: Precambrian to Paleozoic. About 15 mi of the line.
Gneiss, mica-schist, amphibolite. Age: Precambrian to Paleozoic. About 7 mi of the line.
Age: Precambrian to Paleozoic. 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 Alpharetta reaches the Gulf of America by way of Big Creek, the Chattahoochee and the Apalachicola: about 430 river miles.
Lakes on the way: Walter F George Reservoir, West Point Lake and Bartletts Ferry Lake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alpharetta; river miles along the main stem, rounded.
