The Bear Valley Strip Mine is an abandoned coal strip mine

Surface mining

Surface mining , is a type of mining in which soil and rock overlying the mineral deposit are removed...

 located in Coal Township, Northumberland County, to the southwest of the town of Shamokin

Shamokin, Pennsylvania

Shamokin is a city in Northumberland County, Pennsylvania, at the western edge of the Anthracite Coal Region. At the 2000 census the population was 8,009 residents...

, Pennsylvania. It lies in the Western Middle Field of the Anthracite belt in the Ridge-and-Valley Appalachians

Ridge-and-valley Appalachians

The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending from southeastern New York through northwestern New...

, where the Pennsylvanian

Pennsylvanian

The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...

 Llewellyn Formation

Llewellyn Formation

The Llewellyn Formation is a mapped bedrock unit in eastern Pennsylvania. It was previously known as the "coal measures" and the post-Pottsville rocks. The formation is named for the community of Llewellyn in Schuylkill County.-Description:...

 is exposed. The property is owned by the Reading Anthracite Company

Reading Anthracite Company

Reading Anthracite Company is a coal mining company based in Pottsville, Pennsylvania in the United States. It mainly mines anthracite coal in the Coal Region of eastern Pennsylvania....

.

Structural geology

Structural geology

Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation in the rocks, and...

The coal and other overlying rock has been removed by mining down to a resistant sandstone bed, revealing the three-dimensional structures of folding

Fold (geology)

The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...

 and faulting caused by the Alleghany Orogeny

Alleghenian orogeny

The Alleghenian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957....

. Students of geology have visited the location for decades due to the quality of exposures.

The central anticline

Anticline

In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships In structural geology, an anticline is a fold that is...

 in the valley is often called the "Whaleback".

The sequence of structural deformation is outlined as follows:

Stage	Deformation event
I	Joint formation in coal
II	Joint formation with quartz Quartz Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...  fiber fillings in sandstone Sandstone Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...  and ironstone Ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical repacement, that contains a substantial proportion of an iron compound from which iron either can be or once was smelted commercially. This term is customarily restricted to hard coarsely...
III	Pressure solution Pressure solution In structural geology and diagenesis, pressure solution or pressure dissolution is a deformation mechanism that involves the dissolution of minerals at grain-to-grain contacts into an aqueous pore fluid in areas of relatively high stress and either deposition in regions of relatively low stress...  and primary crenulation cleavage Cleavage (geology) This article is about rock cleavage, for cleavage in minerals see Cleavage Cleavage, in structural geology and petrology, describes a type of planar rock feature that develops as a result of deformation and metamorphism. The degree of deformation and metamorphism along with rock type determines the...
IV	Conjugate wrench and wedge faults form
V	Large-scale folding
VI	Extensional jointing and faulting