"A sprawling chain of volcanic islands and atolls in the central Pacific Ocean has grown in size over the past 70 years, despite sea level rises, a new study shows.
... (see) recent picture(s) of part of the island, with the outline of the land in 1943 in red.New Zealand and Canadian researchers studied an island on Ailinglaplap Atoll in the Marshall Islands using aerial photographs, satellite imagery and radiocarbon dating of sediment deposits.
They found the island, which has about 40 homes, has grown 13 per cent from 2.02 square kilometres in 1943 to 2.26sq km. It got to 2.28sq km in 2015.
Sediment build-up appeared to have caused the merging of what had been two separate islands, and a spit at the western end of the island was continuing to extend, adding to the land area above sea level, the study found.
Radiocarbon dating was used to calculate the ages of coral fragments, shells and microscopic marine organisms at the island’s western end. The sediment deposits were from more recent material, generally after 1950.
Atolls are rings of coral, with islands on top of the coral and a lagoon inside the ring.
University of Auckland senior lecturer Dr Murray Ford, a coastal geo-morphologist who worked on the study, said the research showed that the atolls essentially depended on the health of the coral reef they were built on.
The study confirmed the modern reef was the source of material that built up the island. Previously it was considered possible that older material being recycled around was causing changes to atolls, Ford said.
The atoll was like a concrete basement made from the reef, while the islands were made of sand and gravel, and because of sea level changes had only typically been around for a few thousand years.
In the area of the Pacific where the study was carried out, sea levels were slightly more than a meter lower now than they were 2000-4000 years ago."
