Ecological Land Type

ELT 170a

Area: 
3127 ha
Area in acres: 
7729 acres
Elevation Range
Minimum: 
924 m
Minimum in ft: 
3031 ft
Maximum: 
1136 m
Maximum in ft: 
3728 ft
Median: 
1002 m
Median in ft: 
3287 ft
Soil Summary: 
very deep, very gravelly and gravelly clay loams, clays, and sandy loams, lime throughout or prevalent at a shallow depth, well developed; also included are very deep sandy loam soils associated with washes and recent alluvial terraces, these soils have little or no development and lack lime in the upper soil layers; dominated by Pima County soil survey map units 6 (Bernardino-Tombstone association, 5 to 16 percent slopes), 79 (Tombstone very gravelly loam, 15 to 50 percent slopes), and 19 (Comoro sandy loam, 0 to2 percent slopes)
Geologic Materials: 
alluvium and residuum associated with Quaternary and Tertiary sandstone, siltstone and conglomerate, undivided (QTs) and Holocene piedmont alluvium (Qy) which comprise 90% and 9% of the unit, respectively
Landforms: 
finely dissected, weakly to moderately incised fan and pediment surfaces

Map with the ELT 170a polygon highlighted.Photo Point 011Photo Point 013Photo Point 014Photo Point 123Photo Point 120

Landform position classes and corresponding vegetation*

Landform Class Area Percentage of ELTsort icon Vegetation and notes
nearly level plateaus or terrace 951 ha 30

whitethorn acacia dominant, with prickly pear and Isocoma

valley flats (or water bodies) 169 ha 5

whitethorn acacia dominant, with mesquite

gently sloping ridges and hills 1749 ha 56

whitethorn acacia dominant, with prickly pear and Isocoma

toe slopes, bottoms, and swales 196 ha 6

whitethorn acacia dominant, with mesquite