Barbury Castle Tetrahedron
FIELD DESCRIPTION
The Barbury Castle Tetrahedron appeared on July 17, 1991 near Barbury Castle hillfort in Wiltshire, England, and marked a watershed moment in crop circle history. Spanning approximately 180 metres, it depicted a tetrahedron — a triangle with a large circle at each corner connected by straight pathways, with internal geometric divisions at the center. The formation was so geometrically precise that researchers used it to calculate the ratio of the circumference to the diameter of the central circle, yielding pi to several decimal places. Soil samples taken by BLT Research showed anomalous iron microspheres embedded in the soil — consistent with a high-energy plasma vortex. It remains one of the most scientifically studied formations ever recorded.
What Are Node Anomalies?
In genuine crop formations, the plant stems are bent — not broken — at the nodes (growth joints). This bending is accompanied by elongated nodes and sometimes expulsion cavities — small holes blown through the node wall from the inside, consistent with a rapid, intense heat source.
Node elongation and/or expulsion cavities confirmed by field investigation. Inconsistent with mechanical flattening.
No node anomalies detected. Formation may be man-made or insufficient investigation was conducted.
Node status not recorded or formation was not physically investigated by researchers.
Research by BLT Research Team (W.C. Levengood, Nancy Talbott) documented node elongation in 300+ formations across 30+ countries. The phenomenon requires a brief, intense electromagnetic or microwave energy source — incompatible with boards and rope.