Full moon helps paint vibrant, muddy ‘brushstrokes’ in Indonesian river — Earth from space
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Where is he? Rokan River, Sumatra, Indonesia [2.2294556537, 100.62990147]
What’s in the photo? Sediment patterns resembling brushstrokes painted by a high tide
Which satellite took the photo? Landsat 8
When was it taken? June 23, 2024
This stunning satellite photo captured a series of “brushstroke-like patterns” that emerged at the mouth of an Indonesian river. The striking streaks were triggered by a particularly high tide after a full “strawberry moon.”
The river flows from the Barisan Mountains in western Sumatra to the island’s northern coast, where it empties into the Strait of Malacca. Here the river transforms into a brackish estuary which flows on either side of Halang Island (photographed).
The Rokan River often has a yellow tint due to the high levels of sand and silt in its waters. Sediment is washed up from the river bottom, in part due to the constant rise and fall of the tide, according to NASA Earth Observatory.
In this image, the tide is about to ebb, slowly carrying sediment out to sea. Seen from above, these “brushstroke-like patterns” transform the river into what looks like an abstract painting, Earth Observatory representatives wrote.
When the photo was taken, high tide was at its peak, up to 5 meters higher than low tide. The water was particularly high as it was the day after the full “Strawberry Moon”. rose in the skyaccording to the Earth Observatory. (The June full moon is nicknamed the Strawberry Moon because it coincides with the strawberry harvest season in the Northern Hemisphere, not because of its color.)
Tidal range is greatest when there is a full moon, because the sun and moon are aligned in a straight line, so they gravitationally push and pull Earth’s oceans in synchrony. This is called a “spring tide,” but it occurs throughout the year.
As well as having a large tidal range, the Rokan River is home to a regular tidal bore – a powerful wave of water that rushes upstream like a giant wave during high tides. This rare phenomenon only occurs in estuaries with narrow mouths and high tidal ranges.
A Study 2022 revealed that rising water levels are responsible for transporting large quantities of sediment up the river. If drilling occurred before the satellite photo was taken (which may or may not have happened), it could have stirred up some of the sediment trails visible in the image.
All this tidal action can have a significant impact on the estuary itself. A 2016 study compared satellite images of the estuary between 2000 and 2014 and found that the coastline along northern Halang Island (which clearly extends beyond the small landmass in the image) is growing at an average rate of 220 feet (67 m) per year.
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