Many long term residents of Lincoln surely remember the famous Hippy Cliffs. Situated to the South-East of Pioneers Park along the Haines Branch of the Salt Creek. It's a sandstone cliff that gives way to to clay. On the high ground there is the Yankee Hill Brick Factory which mines the materials deposited in the area and turns them into...well brick.
The layout is about what you'd expect from this area. A long, winding river with deep-cut meanders. Pine trees and grasses. A fairly standard off-the-beaten trail place.
The Hippy Cliffs are a very interesting geological feature noted for their high porosity but low permeability. Water tenders to roll right down the cliffs and into the creek below. Water lacking the kinetic energy to reach the creek pools and dries slowly. At the foot of the cliffs water remained from the most recent rain four days prior. This could also be noted in the clay and sandstone which retained vegetation, which would still ex-foliate upon contact. Research into these caves showed a very old system, dating back decades since the initial exposure.
One interesting feature of the Hippy Cliffs is at the top of the feature seen in the photo. There is a kind of "drainage crown" which features a large, bowl-like area which funnels down into a drainage draw. Note the spur raised in the center. This drainage leads to the ground where a deep cave is worn into the sandstone.
Vegetation appears along the raised ridge visible in the photo. I believe this gives the sandstone a degree of stability not seen in other areas.
The large area and the location of this drainage crown lead me to conclude that it is a source of major drainage. Due to sandstone's low permeability water slides down this fairly steep grade at a rapid pace. Snow contributes greatly, no doubt, due to the large, open nature of the feature. The expansion and contraction of the sandstone split this feature further.
This drainage feature connects to another, a seasonal spill over creek up the hill coming from the brick yard down to the creek. Both of which are active mostly during spring thaws and heavy downpours. The composition of the cliffs is the same as the brickyard's, indicating a large deposit of these materials down to the bedrock of increasingly dense sedimentary material. Although not exposed in this photograph the deeper portions of the area contain compacted, stratified clay.
The final noteworthy feature on this expedition is around the corner from the Hippy Cliffs. The river flows in a North-East direction and consequently the gradient's average height decreases. At lower elevations the
exposed clay is highly stratified and jointed. The lower portion of the exposed clay is smoothed due to the river flow both at the time of investigation and during the recent peak in the river's height. Slow movement along the lining of the river showed alternating sections of smooth and rough terrain with occasional river oyster remains stuck into the clay. The regolith is fairly shallow at the site of exposure. Only two feet of soil remain on top of the claystone. At the bottom of the cliff are a series of broken off boulders and a thick,, viscous substance of wet clay pooling near the river's edge. A foot will easily sink in deeply to the unaware visitor. This area of the creek also has the distinction of being the deepest area within the Pioneer's Park drainage matrix.
In summation, the large deposit of sandstone building on clay with it's covering of soil create a very distinctive environment. It's a system of intense drainage, exposed foundational components and overgrown vegetation which creates alternating sections of smooth, sturdy, rough and unstable. Anyone daring to make the trip is certainly in for a pleasant day of geological possibility.
