LOCATION IHUANU                  HI

Established Series
MRK-RTG
05/2012

IHUANU SERIES

The Ihuanu series consists of moderately deep, well drained soils that formed in basic volcanic ash and cinders in `a`a lava. Slopes range from 10 to 20 percent. The mean annual rainfall is about 1140 millimeters (45 inches), and the mean annual temperature is about 13 degrees C (55 degrees F).

TAXONOMIC CLASS: Medial-skeletal, amorphic, isomesic Humic Haplustands

TYPICAL PEDON: Ihuanu very cobbly medial silt loam, on a south facing, slightly convex, 15 percent slope under dry land forest at an elevation of 1326 meters (4350 feet.) (Colors are for moist soil unless otherwise noted. All textures are "apparent field textures". pH measured with organic dyes. When described on September 4, 1997, the soil was dry to 5 centimeters {2 inches} and slightly moist below.)

A/2C1--0 to 5 centimeters (0 to 2 inches); black (10YR 2/1) very cobbly medial silt loam, very dark grayish brown (10YR 3/2) dry; strong very fine granular structure; soft, friable, nonsticky and nonplastic; nonsmeary; many very fine and fine, and few medium roots; many very fine interstitial pores; 2C material consists of unconsolidated `a`a lava fragments (20 percent subangular gravel and 20 percent angular cobbles); strongly acid (pH 5.2); abrupt wavy boundary. (3 to 8 centimeters {1 to 3} inches thick)

2C2/Bw--5 to 50 centimeters (2 to 20 inches); very dark brown (10YR 2/2) extremely cobbly medial sandy loam, dark yellowish brown (10YR 3/4) dry; weak very fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; nonsmeary; common very fine and fine, and few medium roots; many very fine interstitial pores; 2C material consists of unconsolidated `a`a lava fragments (25 percent subangular gravel and 40 percent angular cobbles); slightly acid (pH 6.1); abrupt wavy boundary. (38 to 50 centimeters (15 to 20 inches) thick)

2C3--50 to 56 centimeters (20 to 22 inches); very dark brown (10YR 2/2) extremely gravelly coarse sand, brown (10YR 4/3) dry; single grain; loose when dry or moist, nonsticky and nonplastic; nonsmeary; many very fine interstitial pores; 70 percent cinder gravels; slightly acid (pH 6.1); abrupt boundary. (5 to 8 centimeters {2 to 3 inches} thick)

2R--56 centimeters (22 inches); hard, massive `a`a blue rock.

TYPE LOCATION: Island of Hawaii, Hawaii County, Hawaii; in Hawaii Ocean View Estates, drive to the northeast end of Palm Parkway; pedon is located 0.2 miles southwest from the end of Palm Parkway and 15 meters (50 feet) makai (downslope) of road. Puu O Keokeo Quadrangle; lat. 19 degrees 8 minutes 31.7 seconds N. and long. 155 degrees 43 minutes 30.3 seconds W. (Old Hawaiian Datum)

RANGE IN CHARACTERISTICS:
Depth to bedrock: 50 to 102 centimeters (20 to 40 inches).
Mean annual soil temperature: 13 to 15 degrees C (55 to 59 degrees F).
Rock fragments: 35 to 60 percent by volume of the pedon and range in size from gravel to stones, but are primarily gravel and cobble size lava rocks.
Surface crust: Occurs in 10 to 20 percent of the area.

A/2C1 horizon
Hue: 10YR or 7.5YR.
Value: 2 or 3 moist or dry.
Chroma: 1 or 2 moist or dry.
Texture: Very cobbly medial loam or silt loam.
Dry consistence: Soft, but hard if surface crust is present.
Soil reaction: Strongly acid or moderately acid (pH 5.1 to 6.0).

2C2/Bw horizon
Hue: 10YR or 7.5YR.
Value: 2 to 4 moist or dry.
Chroma: 2 to 4 moist or dry.
Texture: Extremely gravelly or cobbly medial sandy loam or loamy sand.
Dry consistence: Soft or loose.
Soil reaction: Moderately acid or slightly acid (pH 5.6 to 6.5) in the Bw horizon.

2C3 horizon
Hue: 10YR or 7.5YR.
Value: 2 to 4 moist or dry.
Chroma: 2 to 4 moist or dry.
Texture: Extremely gravelly or cobbly loamy sand or sand.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Ihuanu soils are on upper elevation, south and east slopes on the upland and the southwest rift zone of Mauna Loa Volcano at an elevation of 1067 to 1646 meters (3500 to 5400 feet). These soils are on all hillslope positions of hilly `a`a flows that are 1,500 to 3,000 years old. Slope gradients range from 10 to 20 percent. The soils formed in basic volcanic ash and cinders over `a`a lava. The mean annual rainfall ranges from 1020 to 1270 millimeters (40 to 50 inches), which is generally evenly distributed throughout the year. The mean annual pan evaporation ranges from 1270 to 1780 millimeters (50 to 70 inches). The mean annual temperature ranges 12 to 14 degrees C (53 to 57 degrees F). The mean summer and mean winter soil temperatures differ by less than 6 degrees C (11 degrees F).

GEOGRAPHICALLY ASSOCIATED SOILS: These are Iwalani and Mawae series. Iwalani soils are medial and have a lithic contact at 5 to 25 centimeters (2 to 10 inches). Mawae soils are organic soils over `a`a lava.

DRAINAGE AND PERMEABILITY: Well drained. Runoff is very low. Permeability is very rapid in the soil and very slow in the underlying bedrock.

USE AND VEGETATION: These soils are used for wildlife habitat and homesites. The natural vegetation ohia lehua (Metrosideros polymorpha) and pukiawe (Styphelia tameiameiae).

DISTRIBUTION AND EXTENT: Kau District, Island of Hawaii; MLRA 160. The series is of small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Island of Hawaii, Hawaii County, Hawaii, 2008. Proposed in 1997.

REMARKS: Soil moisture - usually moist, but dry in some or all parts for short intermittent periods totaling 90 or more days (Ustic moisture regime).

Diagnostic horizons and features recognized in this pedon include:
--Mollic epipedon - from 0 to 50 centimeters (0 to 20 inches) (A/2C1 and 2C2/Bw horizons).
--Andic soil properties - from 0 to 56 centimeters (0 to 22 inches) (A/2C1, 2C2/Bw, and 2C3 horizons).
--Lithic contact - at 56 centimeters (22 inches) (2R horizon).

Editlog: 2/5/08 Andic texture modifiers added to horizon texture. MRK

Comment on horizonation: The aa lava flowed and then a nearby cinder cone erupted. At first it was a cindery ash fall and then eventually finer ash on top which can happen during an eruption episode. The aa lava fragments and the aa bluerock are from a single depositional event and the larger to finer particle ash fall is one as well. There were only 2 depositional events here. MRK

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National Cooperative Soil Survey
U.S.A.