Hot gasses propelled globs of lava high into the air, and as this lava fell back to the ground it quickly formed dramatic, hollow spatter cones. Later, less explosive lava flowed out and created the massive Devils Homestead flow. The magma that formed both features rose through a long fissure in the ground that runs along Gillem Bluff. Weak spots in the surface like this one allow magma to erupt and form a multitude of different volcanic features.