The album was released on October 15, 1990 just four months after the crop circles appeared on July 12, 1990.  The famous crop circle appeared in East Field, Alton Barnes, in Wiltshire UK.  It consisted of swirled circles, concentric rings, keys, spurs and coffin-like boxes, all linked together by a long corridor of flattened crop.

Here’s a ground level close-up.

Click below for the Google Satellite link.

To me the crop circles are very similar to Led Zeppelin symbols.

Click the story below for the story about the ZOSO meanings.

Led Zeppelin IV “ZOSO” Symbol Meanings