Battlefield Geology, Part 2: Outcrop and Boulders of the Devil's Den | Gettysburg National Military Park, Pennsylvania, USA
Now a favorite spot for playing children, the Devil's Den was on 2 July 1863 the scene of a fiercely contested action between Federal and Confederate soldiers. Both forces suffered heavy losses from their inability to entrench on this exposed, stony ground.
While the Southern troops eventually drove their enemy from this location, they were unable to secure the heights of Little Round Top nearby and thereby failed to turn the Union army's left. Had they done so, they could have gone on to stage a surprise attack from the rear that might have profoundly changed the course of American history.
As it was, the battle was decided the following day when General Robert E. Lee's massive frontal attack on the Union center ("Pickett's Charge") failed disastrously.
Approximately 200 Ma before, near the beginning of the Jurassic period, the Gettysburg area was part of a great rift system created by the breakup of the supercontinent Pangaea. As the crust was stretched, bodies of magma rose—some reaching the surface as volcanic eruptions, and others being emplaced at shallow depth as sills. The rock here, the York Haven Diabase, was part of the latter, and only later was exposed by the forces of erosion.
To see the other photos and descriptions of this series, visit
Battlefield Geology, Part 2: Outcrop and Boulders of the Devil's Den | Gettysburg National Military Park, Pennsylvania, USA
Now a favorite spot for playing children, the Devil's Den was on 2 July 1863 the scene of a fiercely contested action between Federal and Confederate soldiers. Both forces suffered heavy losses from their inability to entrench on this exposed, stony ground.
While the Southern troops eventually drove their enemy from this location, they were unable to secure the heights of Little Round Top nearby and thereby failed to turn the Union army's left. Had they done so, they could have gone on to stage a surprise attack from the rear that might have profoundly changed the course of American history.
As it was, the battle was decided the following day when General Robert E. Lee's massive frontal attack on the Union center ("Pickett's Charge") failed disastrously.
Approximately 200 Ma before, near the beginning of the Jurassic period, the Gettysburg area was part of a great rift system created by the breakup of the supercontinent Pangaea. As the crust was stretched, bodies of magma rose—some reaching the surface as volcanic eruptions, and others being emplaced at shallow depth as sills. The rock here, the York Haven Diabase, was part of the latter, and only later was exposed by the forces of erosion.
To see the other photos and descriptions of this series, visit