A couple of weeks ago, the silence of the neighborhood where I live in Laguna Hills was disturbed by the racket of a news chopper overhead. This is not an uncommon occurrence since accidents on nearby Interstate 5 and the CA-73 toll road attract the news media on slow news days, so I took no immediate notice. A few minutes later, while taking a break, I turned the television on and saw a quick teaser regarding a “sinkhole” that was threatening a neighborhood in Laguna Niguel, with an entire neighborhood evacuated due to the threat of a landslide. I finally caught a newscast that focused on the incident. While an aerial view of the “sinkhole” appeared on the screen, the news commentator grilled an Orange County fire official on the impending disaster. What I saw on the screen was the raw end of a water main that had blown apart near the top of a graded slope, with some erosion of the slope face below due to the water gushing from the pipe before it could be turned off. Several times during the interview, the fire official corrected the reporter that the incident was, in fact, in the City of Laguna Hills and not Laguna Niguel as reported and that there was slope erosion and some flooding, rather than any ground sinking (i.e. “sinkhole”). The City was in the process of having the slope and immediate area checked for more serious ground movement by a soils engineer. Later that day, my wife and I were driving down one of the main boulevards in our area and we noticed an ABC Channel 7 news van hotfooting its way into our otherwise un-newsworthy area of south Orange County. We caught the full news broadcast late that night, with the newscasters still referring to the incident as a “sinkhole,” and discovered that the water line was located only about two blocks from where we live. This is an area I am geologically familiar with, since I was the staff geologist in charge of the grading for this and surrounding developments in Aliso Viejo in the early 1980’s.
Why is it that the news media, in reporting ground movement ranging anywhere from collapsed street pavement to landslides, refers to everything as a “sinkhole?” This has always been a mystery to me. The term “sinkhole” refers to a very specific geologic phenomenon.
The Glossary of Geology, by Bates and Jackson, defines a sinkhole as follows:
“A circular depression in a karst area. Its drainage is subterranean, its size is measured in meters or tens of meters, and it is commonly funnel-shaped.”
The key here is the term “karst,” which the glossary defines as:
“A type of topography that is formed on limestone, gypsum, and other rocks by dissolution, and that is characterized by sinkholes, caves, and underground drainage.”
In the long run, maybe this misuse of terminology only matters to someone who knows the difference. But, to those of us who are somewhat tasked with educating the public with regard to geologic hazards, it is difficult to accept at times, and I can still hear the ranting of my professor whenever I hear the term "sinkhole" in a news report.