Сансраас авсан далайн ландшафтын дүрслэл нь хорь орчим жилийн туршид өөрчлөгдөөгүй дүр төрхөө хадгалж, эрдэмтдийн анхаарлыг татсаар байна.
NASA-гийн Landsat 7 хиймэл дагуулаар 2001 оны нэгдүгээр сарын 17-нд авсан Багамын их банкны дүрслэл нь далайн экосистемийн судалгаанд чухал ач холбогдолтой баримт болжээ. Далайн судлаач Серж Андрефуэ уг зургийг дэлхий дээрх далайн ёроолын өвөрмөц тогтоцтой, давтагдашгүй үзэгдэл гэж тодорхойлсон байдаг. Энэхүү зураг нь NASA-гийн “Millennium Coral Reef Mapping Project” төслийн хүрээнд хийгдсэн бөгөөд 2020 онд “Tournament Earth” шалгаруулалтад түрүүлж, олон нийтийн анхаарлыг дахин татсан юм.
Геологийн хувьд уг бүс нутаг нь мөстлөгийн үед хуурай газар байсан бол далайн түвшин нэмэгдэхийн хэрээр усны гүн нь хоёр метр хүртэлх гүехэн тавцан болж хувирчээ. Ёроолын цагаан өнгийн карбонат элс, шохойн чулуу болон далайн өвсний тархалт, усны гүний ялгаа нь сансраас харагдах цэнхэр, ногоон өнгийн солонгорол бүхий өвөрмөц хээг үүсгэдэг. Энэхүү хээ нь хүчтэй далайн урсгалын нөлөөгөөр үүссэн элсэн манхны налууг дагасан хэлбэр дүрс юм.
Landsat 7 хиймэл дагуулын өмнөх үеийнхээс илүү нарийвчлалтай цэнхэр спектрийн мэдрэгч нь эрэг орчмын гүехэн ус болон шүрэн хадны тогтоцыг тодорхой харах боломжийг бүрдүүлсэн. 2020 оны хоёрдугаар сарын 15-нд Landsat 8 хиймэл дагуулаар дахин ажиглахад уг бүс нутгийн доорх хэв шинж бараг өөрчлөгдөөгүй хэвээр байв. Энэхүү мэдээлэл нь шүрэн хадны цайралтыг хянах, дэлхийн далайн экосистемийн төлөв байдлыг үнэлэхэд өнөөг хүртэл ашиглагдаж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
One of the most recognizable satellite views ever published by NASA Earth Observatory continues to attract attention nearly two decades after its debut. Beyond its striking appearance, the image of the Great Bahama Bank has become a valuable record of a marine landscape that has remained remarkably consistent over time.
Originally published as NASA Earth Observatory’s Image of the Day in 2002, the scene returned to the spotlight after winning the publication’s Tournament Earth 2020, surpassing a field of much newer satellite images. Oceanographer Serge Andréfouet, who first identified the image’s uniqueness, said he was not surprised by its lasting popularity.
The image also reflects an important period in coral reef research. It was collected during the Millennium Coral Reef Mapping Project, a NASA-funded initiative launched to improve global knowledge of reef systems at a time when available maps had changed very little since the nineteenth century.
A Shallow Marine Platform Shaped By Ancient Processes
The colorful swirls seen across the Great Bahama Bank are the result of geological history and the continuous movement of water across the seafloor rather than a temporary natural event.
NASA Earth Observatory explains that the bank was exposed as dry land during past ice ages before gradually disappearing beneath rising seas. Today, the platform is covered by shallow water that reaches depths of only two meters, or seven feet, in some areas. Its surface is composed primarily of white carbonate sand and limestone produced from the skeletal remains of corals. The publication also notes that similar deposits contributed to the formation of the Florida peninsula.
The curved patterns visible from space are underwater sand ripples following the slopes of submerged dunes. They were probably shaped by relatively strong currents flowing near the seabed. Variations in the amount of sand and seagrass, combined with differences in water depth, create the distinctive shades of blue and green that define the image.
The Satellite View That Captured Worldwide Attention
The famous scene was acquired on January 17, 2001, by the Enhanced Thematic Mapper Plus (ETM+) instrument aboard Landsat 7, using spectral bands 1, 2 and 3.
As reported by the NASA, the satellite’s blue spectral band made it easier to distinguish shallow-water features than earlier satellite missions. That capability proved particularly valuable for observing coastal environments and reef systems. For Serge Andréfouet, the image stood apart from the moment he first saw it.
“There are many nice seagrass and sand patterns worldwide, but none like this anywhere on Earth,” he said. “I am not surprised it is still a favorite, especially for people who see it for the first time.”
Over the years, the image has appeared on countless websites, in books, and even at rave parties. When Landsat 8 revisited the same location on February 15, 2020, the underwater patterns appeared largely unchanged.
A Landmark Image For Coral Reef Research
The shallow waters of the Great Bahama Bank end abruptly at the Tongue of the Ocean, a deep marine basin descending about 2,000 meters (6,500 feet). The area is home to more than 160 fish and coral species and lies alongside Andros Island, which supports one of the world’s largest fringing reefs.
A wider view of the region was later recorded on April 4, 2020, by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite, highlighting the contrast between the bright, shallow bank and the darker surrounding waters.
The image was originally acquired as part of the Millennium Coral Reef Mapping Project, which ultimately collected more than 1,700 Landsat 7 images. The space agency reports that Landsat 7 was the first mission in the program capable of imaging both coastal waters and the open ocean. The same source adds that reef maps produced from satellite observations are now used alongside sea surface temperature data to identify areas that are vulnerable to coral bleaching and to monitor the condition of coral reef ecosystems worldwide.
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