We were sent to a map a Hohokam platform mound, circa 1150-1300 AD, in the middle of the desert east of the Pichacho Peak area.
Arizona had had very unusual wonderful spring rains. Each side of the long desert dirt road to the site was blanketed with wild flowers. Absolutely covered in beautiful lavender as far as the eye could see in all directions.
This boded ill for mapping.
How were we to map the site if it was covered in vegetation? What could we expect to see? Certainly not the adobe melted, ground level walls of the rooms or the compound walls surrounding the platform.
We arrived, parked and did the usual shooing cows with a loud "Hi Ya" then rolled under the barbed wire fence.
The flat area approaching the mound was nude, just desert earth - no vegetation; an occasional potsherd here, a lithic there - but nothing astounding yet signaling greater things ahead.
We could see the mound rising up about 3 meters above the desert floor. It was covered in ground hugging weeds!
What we saw when we got atop the mound really astounded us.
The walls of the rooms and the compound walls were fully visible! On the entire site, walls were completely delineated by the lack of weeds - walls showing each room even the entryway into the rooms. The vegetation had grown right up to the walls but since the walls were adobe the weeds did not grow on them.
We spent ecstatic hours pin flagging, taking pictures and mapping each wall. We had a fantastic map of the site.
Later we learned: southwest archaeologists, who are used to dealing in 100 year spans, call this vegetation anomaly the “Brigadoon Effect”!