High Ridge Park
Several decades ago Virginia pine constituted a much larger proportion of the woodland than it does today. Mature pines are dying (a normal aspect of succession) while the understory of mountain laurel and lowbush blueberry indicates that the soils remain highly acidic, a by-product of the diverse soil formation processes of the upper Coastal Plain.
Here deep well-drained Chillum loam, with its loess overburden dropped by glacial winds, and ocean-born Sassafras loam (Maryland's State Soil) cap the high ridges. Washed of base elements on their way to the sea, the eroded remnants of the once-mighty Appalachians are the parent material for these extremely acidic Coastal Plain soils.
Seasonally perching and storing water near its surface, poorly drained sandy Fallsington loam (formed in the same marine sediments as Sassafras) fills the ridge depressions. Where not drained by deeply scoured incised stream channels, this wetland soil tasks the plant community forcing natural selection of only those species that are adapted to life in the hydric soil environment. Slowly seeping laterally, this same ground water gives rise to the intermittent streams that drain the hilltop and flow steeply down into the deeply cut Patuxent River Valley.
In several locations these sediments have eroded away as the ancient Patuxent and its tributaries slowly cut downward exposing the underlying gneiss of the Piedmont bedrock. On the resulting valley slopes this parent material weathered to form rocky but fertile Manor loam and the shallower Brinklow channery loam. In some bottoms the wetter Glenville silty clay loam developed with a seasonal perched watertable that restricts root development and shapes the herbaceous and woody plant community arising from it.
With both alluvial Coastal Plain and residual Piedmont parent materials and the deeply cut Patuxent River valley, the geological position on the Fall Line gives the park a complex soil environment with many natural features shaping a diverse wildlife habitat.
Rockburn Branch Park
Lying well into the Coastal Plan, the soils of Rockburn Branch Park formed in very old sandy sediments, remnants of the ancient Appalachians. Due to the washing away of basic minerals during transport, excess soil acidity ties up vital nutrients playing a major selective role in the type of vegetation and in plant succession.
Much of Rockburn's hilltops and slopes are capped with Sassafras loam, Maryland's State Soil. Once covered by oak forests, it is a wide ranging soil with economic importance to Maryland's agriculture. Centuries of weathering have worn down the sands into silts and clays making Sassafras a deep, well-drained, and fertile soil.
The somewhat detached southeastern component of Rockburn is predominately Russett fine sandy loam. Sandier than Sassafras and extremely acidic, this moderately well-drained soil has a shallow seasonal watertable. The combination of acidity and subsoil saturation creates a uniquely inhospitable soil environment for both flora and fauna.
The park's shallow draws and depressions are lined with poorly-drained Fallsington loam. With ground water often reaching to the surface, this is a hydric (wetland) soil. In such saturated conditions, a unique group of plants and trees grow with specific physical adaptations to transport oxygen to their roots.
The park's one major stream corridor, Rockburn Branch, is dominated by much younger soils. Forming in a more stable geological era, and where not eroded away by stream meandering, moderately well-drained Codorus and poorly-drained Hatboro silt loams are found. Weathered from deposits of locally eroded soils, both developed in active floodplains throughout the county.