On Shale (IMAGE) Penn State Caption This photo shows big northern red oaks growing on top of the Rose Hill Shale formation. Researchers found that the maximum tree height in plots underlain by shale is, on average, more than 19 feet higher than in plots underlain by sandstone. Credit Warren Reed, Penn State Usage Restrictions non commercial use only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.