They were formed over a few million years near the end of the Cretaceous when huge volumes of lava were released in a series of eruptions. Other sites of possible massive volcanic eruptions have been found in Cameroon and the Coral Sea. Large scale eruptions would have resulted in several trillion tonnes of ash and toxic gases, such as sulphur dioxide and carbon dioxide, being pumped into the air.
These could cause catastrophic changes to the climate including prolonged winters, seasonal changes, global warming and aridity, along with other impacts such as acid rain, and chemical changes to the ocean surfaces.
The Deccan eruptions certainly affected local flora and fauna, but evidence suggests that it may have had little direct affect on global extinctions. Fossils found around the Traps show that life was resilient in this environment, including dinosaur life. The Deccan Traps in India cover an area of , square kilometres. Basaltic lava specimen, DR From the Deccan Traps, India. Late Cretaceous 65 million years ago. Another possibility suggested by some scientists is that a variety of factors, none of which were individually decisive, caused the mass extinctions at the end of the Mesozoic.
The extinction 'event' took millions of years with the final extinction coinciding with the meteorite impact. Fossil and geological evidence indicates gradual changes on a global scale were taking place before the end of the Cretaceous. These changes included volcanic activity, shifting continental plates that altered the climate and environment, falling sea levels and mountain building. Significant plant extinctions were occurring at this time and the fossil record in some areas suggests that dinosaur populations were also in decline.
Scientists agree in a number of areas. For instance, they agree that at the end of the Cretaceous the global climate was changing, that there was major continental plate movement and ocean regression, that increased volcanic activity was occurring, that dinosaur diversity was declining and that a meteorite impacted.
However, they differ in their assessment of the evidence and the degree to which each factor contributed to the mass extinction event. Part of the reason they interpret the evidence differently is due to the lack of fossils and sample sites from the end of the Mesozoic only the northwest USA has been extensively studied. In addition, a lack of knowledge about dinosaur physiology and its role in their extinction, along with why some animal groups died while others survived, makes definitive answers almost impossible.
Finding out what caused the mass extinction is one thing. How and why some groups of animals survived when others did not is another. Unfortunately, gaps in the fossil record and our knowledge about the extinction event mean we may never have all the answers.
A few patterns do emerge. Life in the seas was hardest hit. Many groups of land animals that were either large or warm-blooded, such as non-avian dinosaurs, pterosaurs and primitive birds, also suffered severe losses. Those that survived tended to live in freshwater rivers or lakes, were small, had widespread distributions or were cold-blooded. Crocodiles and alligators are often viewed as the great survivors from the dinosaur age, and also mistakenly as living dinosaurs.
The question is often asked as to why and how they survived this mass extinction when non-avian dinosaurs did not. Firstly, not all crocodile families did survive - in fact, quite a number did become extinct, particularly the large-bodied ones.
A number of reasons have been suggested to explain why the other groups of crocodiles did survive. These include:. Birds are a highly successful group with about 10, living species but their continued survival, along with that of many other animals, depends largely on us.
We are currently contributing to another mass extinction event. The Australian Museum respects and acknowledges the Gadigal people as the First Peoples and Traditional Custodians of the land and waterways on which the Museum stands. Image credit: gadigal yilimung shield made by Uncle Charles Chicka Madden. This website uses cookies to ensure you get the best experience on our website. Life slowly rebounded, eventually giving way to a flourishing diversity of animals, from massive lizards to monstrous dinosaurs.
The Triassic period , from million to million years ago, saw the rise of reptiles and the first dinosaurs. The Jurassic period , from about million to million years ago, ushered in birds and mammals. And the Cretaceous period , from million to 66 million years ago is known for its iconic dinosaurs, such as Triceratops , and pterosaurs such as Pteranodon.
Coniferous plants, or those that have cone-bearing seeds, already existed at the beginning of the era, but they became much more abundant during the Mesozoic. Flowering plants emerged during the late Cretaceous period. The lush plant life during the Mesozoic era provided plenty of food, allowing the biggest of the dinosaurs , such as the Argentinosaurus , to grow up to 80 tons, according to a study in the journal Revista del Museo Argentino de Ciencias Naturales.
Earth during the Mesozoic era was much warmer than today, and the planet had no polar ice caps. During the Triassic period, Pangaea still formed one massive supercontinent. Without much coastline to moderate the continent's interior temperature, Pangaea experienced major temperature swings and was covered in large swaths of desert. Yet the region still had a belt of tropical rainforest in regions around the equator, said Brendan Murphy, an earth scientist at St.
Francis Xavier University in Antigonish, Canada. The Mesozoic era was bookended by two great extinctions, with another smaller extinction occurring at the end of the Triassic period, Olsen said. Around million years ago, the end-Permian extinction wiped out most life on Earth over about 60, years, according to a February study in the journal Proceedings of the National Academy of Sciences PNAS. At the end of the Triassic period, roughly million years ago, most amphibious creatures and crocodile-like creatures that lived in the tropics were wiped out.
The few incomplete dinosaur fossils found are likely from animals that died, floated out to sea, and sank.
Seas covered western and central Kansas during the late Cretaceous Period. Fossilized marine rocks found at the surface include the Greenhorn Limestone in central Kansas and the Niobrara Chalk to the west. The Greenhorn Limestone consists of chalky limestone beds alternating with thicker beds of grayish shale.
Near the top of the Greenhorn is a limestone bed called Fencepost limestone. Because timber was scarce in this part of the state, limestone was used extensively by early settlers for buildings and fenceposts.
The Niobrara Chalk beds, which were deposited in the deeper part of the Cretaceous ocean, are known for the awe-inspiring chalk remnants such as Castle Rock and Monument Rocks in Gove County. Fossils of marine reptiles such as plesiosaurs and mosasaurs have been found in the Niobrara.
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