Sailing Stones

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Audio question

1. AThe lecturer explains that the movement of the rocks was eventually attributed to small earthquakes, which shake the lakebed and cause stones to slide downhill along a gentle slope. Although researchers installed GPS units in 2014, they never witnessed a movement directly and concluded that the slope and seismic activity together account for the trails left behind.
2. BHeavy rocks on Racetrack Playa in Death Valley leave long trails but had never been seen moving until 2014, when researchers using GPS and time-lapse cameras observed the process. A shallow winter pond freezes into very thin ice, which breaks into floating panels as it melts; a light breeze pushes these panels, shoving the rocks slowly across the soft mud beneath.
3. CRocks on Racetrack Playa move when extremely strong desert winds, sometimes reaching hurricane force, drag them across the dry surface. The 2014 researchers confirmed this using GPS units and cameras, observing that only the heaviest rocks remained still. The lecturer notes that trails form in dust rather than mud, which is why they are visible all year round.
4. DThe sailing stones remain an unsolved mystery. The lecturer describes how researchers set up cameras in 2014 but recorded nothing, leaving thick ice sheets dragged by storms as the leading theory. Because the playa receives no rain, no pond can form, so scientists now believe the trails were created by pranksters moving the rocks at night over many decades.

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Source: Pearson, PTE Academic & UKVI test format, Part 3: Listening, checked 9 October 2026.