Orsi and his colleagues analyzed samples from sediment cores similar to this one. Cores are collected by driving long pipes deep into the sediments, then withdrawing them with sediment inside. Back in the lab, each pipe is split down the middle, giving researchers access to the interior of the core. The age of a particular sample is determined in part by measuring its distance from the top of the core (which was at the seafloor). Other methods used to date samples include radiocarbon dating and assessing the microfossils embedded in the sediments. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)[back]
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