Rock Run Conglomerate

July 08, 2021


Photographer: Joshua Milden

Summary Author: Joshua Milden & Cadan Cummings

Found on the stream bed of Rock Run near Ralston, PA, this sample of conglomerate consists of well-rounded quartz and plagioclase feldspar clasts. Conglomerate is a sedimentary rock composed of small rock granules (~ 0.08 in or 2 mm) cemented together by a blend of calcium carbonate, iron oxide, and silica. Typically, a mixture of sand, silt, and clay fills the airspace between the rounded rocks. If the rock sample consists of angular, broken granules fragments it is instead called a breccia. The pictured conglomerate sample measures about 2 in (5 cm) thick and 5 in (13 cm) long.

Rock Run is in the McIntyre Wild Area and features many beautiful natural streams and waterfalls. The stream is a tributary to Lycoming Creek and is fed by Baumunk Lake.

Photo data: LG Stylo 5 rear camera. ISO 50, automatic WB, focal length 3.159 mm, exposure time 1/40 sec


View Larger Map