Cretaceous–Paleogene extinction event Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction, was a sudden mass extinction of some three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as the leatherback sea turtle and crocodiles, no tetrapods weighing more than survived. It marked the end of the Cretaceous period and with it, the entire Mesozoic Era, opening the Cenozoic Era that continues today. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can
Geography of Switzerland term covers entire geological movements contributing to the of the Alps’ formation. A crystalline basement formed at the beginning of the Paleozoic era, between 540 and 360 millions years ago. Later, between 205 and 96 million years ago, the alpine ocean or Tethys Ocean formed between Eurasia and Africa. The ocean reached its maximum width at the end of Jurassic period, 135 million years ago. The collision between the Eurasian and African plates made it progressively disappear. This plate collision (still in progress) began 100 million years ago. The Alps resulted from this geological movement, the two plates creating folding