“Not instantaneous in the sense of a meteor impact, but certainly fast geologically speaking, happening in thousands and thousands of years.” The extinction “happened really quite quickly,” Wignall says. The boundary exists where the mountain appears to step to the right, about halfway up the mountainside. Mountains in Svalbard, Norway, record the PT boundary, as well as the PT mass extinction. This situation leads to ocean waters that lack sufficient oxygen to sustain life, thus the mass extinction. And warmer oceans, Wignall explains, have a tougher time retaining dissolved oxygen in their waters than colder oceans do. When Earth warms, its oceans warm as well. The latter would have helped to warm the ancient world. The Siberian volcanoes ejected about 3 million cubic kilometers of lava, as well as greenhouse gases like carbon dioxide. The trigger of the PT extinction, at least in the oceans, was likely massive volcanism in what is today Siberia, explained Wignall. “It’s kind of a top-down recovery, rather than bottom-up, as might be expected,” he said. The findings are a bit of a puzzle, noted Michael Benton, a vertebrate paleontologist at the University of Bristol who was not involved in the new research. “It’s kind of a top-down recovery, rather than bottom-up, as might be expected.” At the same time, he noted, “life on the seafloor was just beginning to recover.” “In the early Triassic, the nekton was diversifying fast,” headed toward “a full recovery,” said P aul Wignall, a paleontologist at the University of Leeds in the United Kingdom who is a coauthor of the new work. These creatures help lay the foundations for the overlying ecosystem to build upon. In light of this new work, the PT extinction appears to buck the usual recovery trend: Ordinarily, the first creatures to rebound after an ecosystem is annihilated tend to be those that live toward the bottom of the food chain. Known as nekton, these kinds of animals included free-swimming predators like the dolphin-like ichthyosaurs and coiled cephalopods known as ammonoids. Persia was eventually conquered by Alexander the Great in 334 B.C.E.The results seem a bit counterintuitive: The first types of organisms to emerge in the oceans, it seems, were animals at the top of the marine food chain. Xerxes depleted the royal treasury with an unsuccessful campaign to invade Greece and continued with irresponsible spending upon returning home. The Persian Empire began to decline under the reign of Darius’s son, Xerxes. Darius also used the tribute money paid to him from each province to fund public works, such as roads and canals. He set up a system of provinces and governors, and a postal service that spanned the empire in order to establish widespread communication. Darius recognized that such a large area needed to be properly structured and organized in order to function efficiently. Cyrus also practiced religious and cultural tolerance toward conquered people.Ĭyrus’s relative Darius I (known as Darius the Great) took the throne after him and built the empire to its greatest height. ![]() He was known to spare the life of a defeated king so that the king could guide Cyrus in successfully ruling over the captives’ subjects. Cyrus was unlike other emperors because he showed mercy toward the cities and kingdoms he conquered. Eventually he was known as Cyrus the Great. From then on Cyrus was called the “ shah,” or king, of Persia. The Persian Empire emerged under the leadership of Cyrus II, who conquered the neighboring Median Empire ruled by his grandfather. ![]() At its height, it encompassed the areas of modern-day Iran, Egypt, Turkey, and parts of Afghanistan and Pakistan. The Persian Empire, also known as the Achaemenid Empire, lasted from approximately 559 B.C.E.
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