LOCATION ARRIVA                  WA

Established Series
IRD TMR/SBC
06/2011

ARRIVA SERIES

The Arriva series consists of very deep, well drained soils formed in layered volcanic ash overlying glacial drift and colluvium. Arriva soils are found on slopes of 0 to 35 percent on ridges and passes of glaciated mountain landscapes. The mean annual precipitation is about 2,540 millimeters and the mean annual air temperature is about 3 degrees C.

TAXONOMIC CLASS: Medial over sandy or sandy-skeletal, amorphic over isotic Thaptic Haplocryands

TYPICAL PEDON: Arriva ashy fine sandy loam, located on a tree and shrub covered northwest facing ridge with a slope of 5 percent and an elevation of 1,900 meters. When described on August 15, 2005 the soil was moist throughout. (Colors are for moist soil unless otherwise noted)

Oi--0 to 4 cm; slightly decomposed needles, leaves, and twigs; common very fine to medium roots; abrupt smooth boundary.

Oe--4 to 23 cm; very dark grayish brown (10YR 3/2) moderately decomposed needles and twigs, dark grayish brown (10YR 4/2) dry; common very fine to fine and many medium roots; common fine to medium irregular pores; very strongly acid (pH 4.6); abrupt smooth boundary.

E--23 to 26 cm; brown (7.5YR 4/2) ashy fine sandy loam, pinkish gray (7.5YR 6/2) dry; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; common very fine to medium roots at top of horizon; common fine irregular pores; very strongly acid (pH 4.8); abrupt wavy boundary.

Oa--26 to 37 cm; very dark grayish brown (10YR 3/2) highly decomposed plant material, dark grayish brown (10YR 4/2) dry; moderate medium subangular blocky structure; common very fine to coarse roots; common fine to medium irregular pores; very strongly acid (pH 4.5); abrupt wavy boundary.

Bw--37 to 47 cm; dark brown (7.5YR 3/2) medial sandy loam, brown (7.5YR 4/2) dry; moderate medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; common very fine to fine and few medium roots; common fine to medium irregular pores; 5 percent granite gravel; very strongly acid (pH 4.8); clear wavy boundary.

Ab--47 to 50 cm; black (10YR 2/1) medial loam, dark gray (10YR 4/1) dry; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic; few very fine to fine roots; common fine and few medium irregular pores; 5 percent granite gravel; very strongly acid (pH 5.0); abrupt smooth boundary.

Bwb--50 to 60 cm; very dark brown (10YR 2/2) gravelly medial sandy loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure; soft, very friable, slightly sticky, slightly plastic; few very fine to fine roots; common fine and few medium irregular pores; 20 percent granite gravel and 10 percent granite cobbles; strongly acid (pH 5.2); gradual wavy boundary.

2C1--60 to 85 cm; light olive brown (2.5Y 5/3) very stony loamy coarse sand, light yellowish brown (2.5Y 6/3) dry; single grain; loose, nonsticky, nonplastic; common medium to coarse interstitial pores; 30 percent granite gravel, 10 percent granite cobbles, and 10 percent granite stones; moderately acid (pH 5.6); gradual wavy boundary.

2C2--85 to 152 cm; light yellowish brown (2.5Y 6/4) very stony loamy coarse sand, pale yellow (2.5Y 7/4) dry; single grain; loose, nonsticky, nonplastic; common medium to coarse interstitial pores; 20 percent granite gravel, 10 percent granite cobbles, and 20 percent granite stones; moderately acid (pH 5.6).

TYPE LOCATION: Skagit County, Washington. Approximately 27 km southeast of the town of Newhalem, along the Sahale Arm trail, North Cascades National Park Service Complex. 795 meters east and 560 meters north of the southwest corner of section 36, T. 35 N., R. 13 E. Willamette Meridian; Cascade Pass, Washington USGS quadrangle; 48 degrees, 28 minutes, 23 seconds north latitude and 121 degrees, 3 minutes, 23 seconds west longitude; UTM 643640 meters E, 5370705 meters N, zone 10N.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature 2 to 8 degrees C. Cryic soil temperature regime.
Moisture control section - dry less than 30 consecutive days. Udic soil moisture regime.
Particle-size control section:
The particle-size control section in this soil is contrasting. Most characteristics are listed by horizon
Clay content - 0 to 10 percent throughout both portions
Rock fragments, medial portion - 5 to 30 percent total, 5 to 30 percent fine to coarse gravel, 0 to 15 percent cobbles, 0 to 5 percent stones
Rock fragments, sandy-skeletal portion - 35 to 55 percent total, 15 to 50 percent fine to coarse gravel, 10 to 30 percent cobbles, 0 to 30 percent stones
Thickness of volcanic ash mantle (medial textural modifier): 36 to 75 centimeters

E horizon
Hue - 7.5YR or 10YR
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 1 or 2 moist or dry
Fine earth texture - ashy FSL or ashy SL
Rock fragments - 0 to 15 percent fine to coarse gravel
Volcanic glass - 35 to 80 percent
Reaction - extremely acid to very strongly acid
Thickness - 0 to 5 centimeters (may not be present in all pedons)

Bw horizon
Hue - 7.5YR or 10YR
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 2 to 6 moist or dry
Fine earth texture - medial SL or medial FSL
Rock fragments - 5 to 30 percent total, 5 to 30 percent fine to coarse gravel, 0 to 15 percent cobbles
Volcanic glass - 15 to 70 percent
Reaction - very strongly acid to strongly acid
Thickness - 5 to 25 centimeters

Ab horizon
Hue - 10YR or 7.5YR
Value - 2 to 3 moist, 3 to 5 dry
Chroma - 1 to 2 moist or dry
Fine earth texture - medial L, medial SL, or medial FSL
Rock fragments - 5 to 30 percent total, 5 to 30 percent fine to coarse gravel, 0 to 15 percent cobbles, 0 to 5 percent stones
Volcanic glass - 15 to 70 percent
Reaction - very strongly acid to strongly acid
Thickness - 2 to 15 centimeters

Bwb horizon
Hue - 10YR or 7.5YR
Value - 2 to 5 moist, 4 to 6 dry
Chroma - 2 to 6 moist or dry
Fine earth texture - medial SL or medial FSL
Rock fragments - 5 to 30 percent total, 5 to 30 percent fine to coarse gravel, 0 to 15 percent cobbles, 0 to 5 percent stones
Volcanic glass - 15 to 70 percent
Reaction - very strongly acid to strongly acid
Thickness - 10 to 35 centimeters

2C horizons
Hue - 2.5Y or 10YR
Value - 4 to 6 moist, 5 to 7 dry
Chroma - 3 to 6 moist or dry
Fine earth texture - LCOS, LS, COS, S
Rock fragments - 35 to 55 percent total, 15 to 50 percent fine to coarse gravel, 10 to 30 percent cobbles, 0 to 30 percent stones
Reaction - moderately acid to strongly acid

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Arriva soils are found on slopes of 0 to 35 percent on ridges and passes of glaciated mountain landscapes at elevations from 1,500 to 2,100 meters. They formed in layered volcanic ash overlying glacial drift and colluvium. The climate is characterized by cool, dry summers and cold, wet winters. Mean annual precipitation ranges from 1,500 to 3,500 millimeters. Mean annual air temperature ranges from 1 to 8 degrees C. Frost-free season is 30 to 60 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Maggib, Mox, Stetattle, and Treen soils. Maggib soils are moderately deep (50 to 100 cm) to a lithic contact and have distinct albic and spodic diagnostic horizons. Mox soils have distinct albic and spodic diagnostic horizons and lack the layered volcanic ash mantle. Stetattle soils lack a contrasting particle-size control section and have a pachic umbric epipedon. Treen soils are shallow (less than 50 cm) to a lithic contact and lack a contrasting particle-size control section.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; high to very high saturated hydraulic conductivity.

USE AND VEGETATION: Arriva soils support wildlife habitat, recreation, and watershed drainage. Native vegetation includes scattered subalpine fir and mountain hemlock, oftentimes in small islands of trees typical of the krummholz zone. Understory species include Cascade and Alaska huckleberry, white and pink mountain-heather, false hellebore, five-leaved bramble, and mountain hairgrass.

DISTRIBUTION AND EXTENT: North Cascade Mountains, Washington. MLRA 3. Series is of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon.

SERIES ESTABLISHED: North Cascades National Park Service Complex, Skagit County, Washington, 2011.

REMARKS: Diagnostic horizons and features recognized in this pedon include:
Particle-size control section - 23 to 123 cm (0 to 100 cm from the mineral surface)
Folistic epipedon - 0 to 23 cm (Oi and Oe horizon
Andic soil properties - 23 to 60 cm (E, Bw, Ab, and Bwb horizons, possibly the Oa horizon)
Cambic horizon - 38 to 60 cm (Bw, Ab, and Bwb horizons)
Thaptic feature - 47 to 60 cm (Ab and Bwb horizons, which are one moist color value unit less than the overlying Bw horizon)
Lithologic discontinuity - 60 cm

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National Cooperative Soil Survey
U.S.A.