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The Cambrian Explosion What is the Cambrian Explosion?!?! What actually happened, was a lot of complex organisms appeared between 543 and 530 million years ago. Organisms like brachiopods (clams, mussels), arthropods (crabs, spiders)and echinoderms (sea stars, sea urchins) appeared in large variations. There is a sudden increase in fossils at the time. Trace fossils also increased abundantly. Soft-bodied Precambrian faunas (animals) can be preserved, however it was difficult (too long ago and no real hardened shells). It is at this period, many organisms attained or improved their shells or bones, or in lay man’s terms (simple terms), hard parts. Environmental Changes? In the Cambrian period, the super continent of Pangaea was breaking up into smaller parts. Continents began to separate. Many climate changes took place at this time. Gases from this period mainly came from volcanic eruptions (sulfur, nitrogen). Oxygen was increasing known as the Great Oxygenation Event, harming organisms that had evolved earlier but giving life to even more organisms. Temperature and rain increased leading to shallow warm seas. Carbon Dioxide was decreasing (this caused the planet to cool down) There was a huge glacial movement and a very harsh ice age. And after the ice age was finished temperatures rose to levels higher than they are today. Environmental Changes Those organisms that were able to survive these vast changes were better adapted holding off extinction. Adaptation: characteristics developed over time that help species survive in particular environments. Extinct: when a species dies. Just an FYI – there was mass extinction of most if not all species from the Cambrian period. Why So Much Life? Many Theories have been created to explain this sudden increase in life, but many contradict each other. One theory was that the changing climate could have caused some of the life created in the period. Impact of Asteroids Did an impact kill the dinosaurs? Large dips in total species diversity in the fossil record. The most recent was 65 million years ago, ending the reign of the dinosaurs. The impact caused climactic changes, temperatures to cool, not allowing dinosaurs to survive. No dinosaur fossils in these rock layers Thin layer containing iridium from impactor Dinosaur fossils in lower rock layers Iridium - evidence of an impact Iridium is very rare in Earth surface rocks but often found in meteorites. Iridium’s daughter element is Platinum. Layers of Iridium were laid down 65 million years ago. Comet or asteroid about 10km in diameter approaches Earth An iridium-rich sediment layer and an impact crater on the Mexican coast 65 million years ago. shows that a large impact occurred at the time the dinosaurs died out, Earth’s Changing Surface Factors that attribute: Thermal Energy Escaping Earths interior (Geothermal) Kinetic Mechanical Potential Plate tectonics Kinetic energy Some of the heat energy in the mantle is transformed into kinetic energy in the form of convection currents that form in the mantle. Kinetic energy Potential energy Kinetic energy of the moving plates can be converted into potential energy when two plates collide and “stick” together. The potential energy builds up until it is finally converted back into kinetic energy and the plates “slip” Plate movement Some of the heat energy from the earth reaches the surface (as in a volcano.) Some heat energy is transformed into mechanical energy in the form of convection currents, moving plates, earthquake waves, flowing lava, etc… Plate movement As plates slide over , under, or past each other, they change the surface of the earth. Plate movement Plates that push together can cause the earth to “crumple” and form mountains. Plate movement When continental and oceanic plates collide, they can produce volcanoes.