Travertine (/'trav∂tin/), noun. White or light-coloured calcareous rock deposited from mineral springs, used in building, eg: “Theyare built of travertine covered with stucco.”
In 1998 I was a lecturer and subject matter expert in the NATO Advanced Study Institute workshop on mineral resource exploitation.
The conference was held in Matráháza, Hungary, less than a decade after the fall of the Berlin Wall, and drew scientists from a number of recently liberated communist bloc countries. Interacting with those folks was an experience in itself.
The workshop included a field trip through north-east Hungary. One field trip stop was near the small village of Egerszalók. As the bus approached the village, the geologist/tour guide pointed to what looked like a pile of steaming snow standing out from the green grassy hillside. A few people were wandering on the “snow” and on the grass surrounding it.
The “snow” turned out to be the Egerszalók travertine, one of the most unique and spectacular travertine sites in central Europe.
This geologic wonder is an indirect product of human activity. In 1961, a 407.5m exploratory oil borehole drilled on the hillside penetrated a highly permeable limestone aquifer. Hot, mineralised water (about 65°C) discharged from the well about as fast as water comes from a fire hydrant. A 30cm deep basin was dug to contain the water and the travertine began to form in the basin.
As the travertine deposit grew, so did the tourist traffic. In 1987, a second well was drilled to supply water for bathing and medical purposes. Water from the first well sustains the development of the travertine mound.
The mound is smaller than a soccer field but impressive nonetheless. The waves of overflowing water create tiny dams called rimstones, and spectacular elements of the travertine mound include curtains, organs, ridges and crests.
Today the deposit is part of a four-star hotel and spa conference resort.
There were no buildings when we were there, only a few tourists bathing in the pools of hot, healing waters.
None of us was dressed for bathing, so we all piled back on the bus happier, but no healthier, than when we arrived. It was the only time I visited a geologic wonder that was younger than I was!
The next stop was to the famous wine cellars of the region. Many of the cellars date back to the early 1600s, when Turkish invaders occupied the region. Residents abandoned their homes and moved into caves dug into the tuffaceous rock hillsides (rock made from volcanic ash). When the invaders left, the residents abandoned the caves and moved back to town. The empty caves were put to a variety of uses, including wine cellars.
Recently, and for a variety of reasons, some of the caves have begun to deteriorate. One of the most interesting reasons is that the area has shifted from well water to municipal water, causing the groundwater to rise.
In turn, leaky water supply lines and sewer lines have exacerbated the deterioration. The rock has very high water absorption, and when saturated some of the minerals rapidly weather to clay. The weakened rocks lead to cave collapse.
To view the problem, we went to look at the tuffaceous rocks and, while there, to taste the wine. The seasoned wine sippers in the group told me it’s essential to expectorate when tasting different varieties of wine.
You swirl your glass, sniff, sip, swish and spit. Geologists sometimes spit on rocks to enhance their colour. But “eeewwwww”, have you ever had an up-close view of those spit buckets? Nasty!