Last week, an approximately 60-tonne M88 Hercules recovery vehicle went missing along with four soldiers close to the Pabrade military training ground in Lithuania. The vehicle was traced to a bog, and after a six-day operation, it was pulled from the swamp. Four soldiers' bodies have also been recovered from the site.

An investigation is ongoing, and it is not yet known how the incident occurred.

Marko Kohv, an applied geologist at the University of Tartu, spoke about the dangers of these environments on Wednesday's R2's morning program.

He said the area where the armored vehicle sank, close to the Lithuanian-Belarusian border, is similar to the Sakala Upland around Viljandi County. At the bottom of old deep valleys, there are often a series of lakes that have become overgrown and turned into bogs.

"In the landscape, these may cover rather small areas, but they can be very deep. In Estonia as well, mud and peat layers tens of meters deep have been measured. If a large vehicle moves over such an area, it can quickly go from firm ground to a very deep spot," Kohv explained.

Maps depicting terrain may not always be accurate, as most of the data originates from the Soviet era. Compared to modern data, discrepancies of tens of meters can occur.

"Nevertheless, the military should not rely solely on GPS when moving heavy vehicles in such conditions. The surroundings of training areas should be thoroughly mapped," he said.

In Estonia, the locations of peatlands from the Soviet era are fairly well known.

"In this case, however, the armored vehicle may not have sunk into a classic bog, but rather into a drained area, which can be more difficult to recognize —especially if one comes from a region where such terrain does not exist," Kohv said.

A drained bog may appear as normal solid ground, even supporting forest growth. In reality, liquid mud may lie beneath it. A walker might not notice the softness of the ground, as the root mat provides support, but a heavy vehicle can fall through.

"That's exactly what happened in Lithuania, the vehicle sank straight down to a depth of five meters," he described.

In Estonia, there are areas with similar deep peat layers, for example, near Suur Munamägi in south Estonia, where former lake basins between high hills have now become overgrown.

"There, up to 17 meters of peat-like material has been measured. Similarly, 14–15-meter-deep peat layers are known in the Karula region. The deepest areas are often located between hills. Looking at the videos from the incident in Lithuania, it seems it took place in a narrow valley, which may be very deep but has filled with peat over time," Kohv explained.

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