Other than national flags, marker flags are perhaps the oldest and most frequently used flags on the continent of Antarctica. These are single-colour flags erected to mark something of note in the landscape.
The flags are meant to be highly visible, so they are usually colours with strong contrast to the snow. Today many of the flags have reflective patches sewn on them.
The flags must also last for months at a time in Antarctica's harsh climate, so they are typically built out of ripstop material. Both today and during the early ages of exploration, marker flags are flown on bamboo poles that can bend in the strong Antarctic winds. Even with these durability measures, marker flags must be replaced every few seasons.
Different coloured flags usually denote different information, but this colour coding is not standard across programs. For example, the British Antarctic Survey uses black for trail flags while the US Antarctic program uses black for hazards.
Depot Flags
Marker flags were a crucial part of long-haul expeditions during the early days of Antarctic exploration. Supply parties would deposit food, fuel, and equipment along a route ahead of the main expedition party. These depots were buried in snow and ice and then marked with a flag, typically black.
In a place where resources are crucial and visibility is low, depot flags could make the difference between survival and death. Ernest Shackleton remembers the sight of the flags fondly in his book about the Nimrod Expedition, 1907-1909.
Started at 6.45 a.m. in splendid weather, and at 11 a.m., while halting for a spell, Wild saw the Bluff Depot miraged up. It seemed to be quite close, and the flags were waving and dancing as though to say, "Come, here I am, come and feed." It was the most cheerful sight our eyes have ever seen, for we had only a few biscuits left.
Trail Flags
Trail flags mark safe, designated routes. These became more common later in Antarctica's history as more routes were established and maintained. They may mark trails for wheeled or tracked vehicles, skis, or foot travel. They are spaced only a few yards apart to allow people to follow them even in near white-out conditions.
Hazard Flags
Hazard flags serve as a warning of crevasses, dangerous melt, unstable ice, and other dangers. In addition to natural obstacles, they also mark man-made obstacles like fuel lines.
Other Marker Flags
In the deep field camps of Antarctica where there aren't adequate toilet facilities, you may see a single yellow mark flag known as the "pee flag." For the curious (and the non-squeamish), more details on the use of these flags can be found here.
Marker flags sometimes appear in crafts and art as well. Antarctic Artists and Writers Program participant Michelle Schwengel-Regala uses marker flags in several of her Antarctica-inspired pieces. You can see more of her work at the online Adequate Earth exhibit (January 28 – May 22, 2021.) Click here to subscribe to future True South updates.