ARCHIVED CONTENT: In December 2020, the CZO program was succeeded by the Critical Zone Collaborative Network (CZ Net) ×

Susquehanna Shale Hills Critical Zone Observatory

Field Areas     

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Our interdisciplinary team works collaboratively in one observatory to advance methods for characterizing regolith, to provide a theoretical basis for predicting the distribution and properties of regolith, and to theoretically and experimentally study the impacts of regolith on fluid pathways, flow rates, and residence times.

0.08 km2   Area

256 - 310 m   Elev

9.5 °C   Temp

1050 mm   Precip

Bare earth Digital Elevation Model from the NCALM Lidar Survey



Soil Order

Inceptisol, Ultisol


deciduous forest

Land Use

forest land

Areas within Susquehanna Shale Hills Critical Zone Observatory

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Setting & Research
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Human Impacts
  • Geology

    • shale

    Bedrock:  The entire catchment is underlain by the thick (>200 m) Rose Hill shale, Silurian age. 

  • Topography

    256 - 310 m elevation

    The Susquehanna-Shale Hills Critical Zone Observatory (SSHO CZO) lies within the Valley and Ridge Physiographic Province of the central Appalachian Mountains in Huntingdon County, Pennsylvania (40º39’52. 39”N 77º54’24.23”W). It is a first order basin characterized by relatively steep slopes (25-35%) and narrow ridges. The stream is a tributary of Shavers Creek (185 km2) that eventually discharges into the Juniata River, a tributary of the Susquehanna River Basin. The SSHO basin is oriented in an east-west direction and the major side slopes have almost true north and south facing aspects. Elevation ranges from 256 meters at the outlet to 310 meters at the highest point in the watershed. The relatively uniform side slopes are periodically interrupted by seven distinct topographic depressions (swales). 

  • Climate

    9.5 °C Mean Annual Temp
    19.0 °C Mean Warmest Month
    -5.4 °C Mean Coldest Month
    1050 mm Mean Annual Precipitation

    SSHO has a humid continental climate. Temperatures average 9.5°C with large seasonal differences: January temperature is –5.4°C, July is 19.0°C. The highest temperature recorded is 33.5°C (April 27, 2009) lowest –24.8°C (January 17, 2009). Annual average relative humidity is 70.2%. Atmospheric deposition in PA is still characterized by acidic (pH~4) precipitation. 2009 water balance: Precipitation 1028 mm, Evapotranspiration 59.4 mm, Recharge 31.9 mm, Runoff 509 mm, with a runoff ratio of 49.6% and interception of 28.4 mm.

  • Ecosystems

    • deciduous forest

    The SSHO forest ecosystem is dominated by oak (Quercus), hickory (Carya) and pine (Pinus) species. Hemlock (Tsuga canadensis), red maple (Acer rubrum), white oak (Quercus alba) and white pine (Pinus strobus) line the deep, moist soils of the stream banks, while on the drier, shallower north and southfacing slopes, red oak (Quercus rubra), chestnut oak (Quercus prinus), pignut hickory (Carya glabra) and mockernut hickory (Carya tomentosa) are dominant, with Virginia pine (Pinus virginiana) only appearing on the north-facing ridge tops. Understory woody species include plants in the Ericaceae family (including Vaccinium spp.), service berry (Amelanchier spp.), hawthorn (Crataegus spp.), raspberry/blackberry (Rubus spp.), sugar maple (Acer saccharum) saplings and witch hazel (Hamamelis virginiana).

  • Soil

    • Inceptisol
    • Ultisol

    Soil Orders at SSHCZO. 

    Shallow to moderately deep, gently dipping to steep, well drained residual shale soils exist on the ridge tops, while along slopes and in the valley bottom soils have formed on a colluvial and alluvial mantle of shale chips. Typical surface soil textures are silt loam, with the percentage of channery shale increasing with depth. Effective rooting depth (depth to bedrock) ranges from 15 cm on ridge tops to 165 cm in some areas on the slopes. Soil structure is moderately developed throughout the basin. Soils are typically saturated along the stream and exhibit redoximorphic features as a result of seasonal soil saturation. A 3 – 5 cm organic layer that contains decaying leaf litter overlies all soils in the watershed.

  • Human Impacts

    • forest land

    Historically, the region was logged for charcoal to support a 19th and 20th century iron industry. Today, SSHO is a relatively pristine forest and good wildlife habitat with little human impact. The basin is primarily available for recreation, education and research. The Penn State forest, of which the basin is a part, is managed for timber with set-asides for research. There are a number of active PSU research projects within the Penn State Forest.