Soil Survey of Crater Lake National Park, Oregon
Crater Lake Institute online library
Detailed Soil Map Units
36—Llaorock-Castlecrest-Rock outcrop complex, 30 to 60 percent north slopes
Map Unit Setting
General location: Side slopes of mountains and ridges
Major land resource area (MLRA): 3
Elevation: 5,500 to 6,500 feet
Average annual precipitation: 50 to 70 inches
Average annual air temperature: 38 to 42 degrees F
Frost-free period: 0 to 50 days
Map Unit Composition
Llaorock and similar soils:
35 percentCastlecrest and similar soils: 30 percent
Rock outcrop: 20 percent
Minor components: 15 percent
Characteristics of the Llaorock and Similar Soils
Setting
Landform: Stratovolcano
Geomorphic position: Side slopes of mountains and ridges
Parent material: Ash over residuum and colluvium derived from andesite
Properties and qualities
Slope: 30 to 60 percent; northwest to northeast aspects
Percentage of surface covered with stones and boulders: 3 percent
Restrictive features: None within a depth of 60 inches
Drainage class: Somewhat excessively drained
Permeability: Rapid
Flooding: Not present
Water table: Not present
Ponding: Not present
Available water capacity: About 9 inches
Interpretive groups
Ecological site: Forestland—(003XY706OR) Tsuga mertensiana/Luzula glabrata var. hitchcockii
Typical profile
Oi—0 to 1 inch; slightly decomposed plant material
A—1 inch to 7 inches; gravelly ashy sandy loam
AB—7 to 14 inches; very stony ashy sandy loam
Bw1—14 to 24 inches; extremely stony medial sandy loam
Bw2—24 to 61 inches; extremely stony medial sandy loam
Characteristics of the Castlecrest and Similar Soils
Setting
Landform: Ashflow
Geomorphic position: Ashfall and ashflows on
mountainsides and ridges
Parent material: Ash and pumice
Properties and qualities
Slope: 30 to 60 percent; northwest to northeast aspects
Percentage of surface covered with stones and boulders: None
Restrictive features: None within a depth of 60 inches
Drainage class: Somewhat excessively drained
Permeability: Rapid
Flooding: Not present
Water table: Not present
Ponding: Not present
Available water capacity: About 6.3 inches
Interpretive groups
Ecological site: Forestland—(003XY706OR) Tsuga mertensiana/Luzula glabrata var. hitchcockii
Typical profile
Oi—0 to 1 inch; slightly decomposed plant material
A—1 inch to 3 inches; paragravelly ashy loamy sand
Bw—3 to 19 inches; paragravelly ashy loamy sand
C1—19 to 26 inches; ashy sand
C2—26 to 38 inches; ashy coarse sand
C3—38 to 64 inches; ashy coarse sand
Characteristics of the Rock Outcrop
Landform:
StratovolcanoGeomorphic position: Lava flows on mountainsides and ridges
Parent material: Andesite
Slope: 30 to 60 percent
Characteristics of the Minor Components
Grousehill soils
Percentage of map unit: 5 percent
Landform: Ground moraine
Geomorphic position: Ash over glacial till on mountainsides
Sunnotch soils
Percentage of map unit: 5 percent
Landform: Debris flow
Geomorphic position: Debris flows on mountainsides
Timbercrater soils
Percentage of map unit: 5 percent
Landform: Ashfall
Geomorphic position: Ashfall and ashflow material on side slopes of mountains and ridges
Major Features and Properties Affecting Management
Llaorock soil
• Rock fragments on surface
• Steepness of slope
• Water erosion
• Rock fragments in soil profile
Castlecrest soil
• Steepness of slope
• Sandy textures
• Low soil strength
• Dustiness if vegetation is removed
• Water erosion
Rock outcrop
• Lack of soil material