Answer:
The oldest rocks of the oceanic crust are found in deep ocean trenches far away from active mid-ocean ridges.
Explanation:
Beginning in the late 1940s, oceanic expeditions continued to map the Atlantic ocean floor using new equipment and collecting thousands of rock samples. These works made it possible to map a gigantic system of submarine mountain ranges, called meso-ocean ridges. By perfecting the method of dating rocks, scientists have been able to determine the true age of seabed rocks. They found that the closer to the mid-ocean ridge the rocks were much younger than imagined, while rocks close to the continents were increasingly older, thus corroborating the Continental Drift.
Answer:
Two possible reasons for the massive extinction at the end of the Paleozoic Era are an asteroid collision and massive volcanic eruptions.
Explanation:
The massive extinction that occurred at the end of the Paleozoic Era is the biggest extinction from what is known so far. The majority of the species died out, and whole families of animals and plants were wiped out of the face of the Earth. It was only small and highly adaptable organisms that managed to survive and give rise to the later life-forms.
The two possible reasons for this massive extinction are an asteroid impact and massive volcanic eruptions. An asteroid collision would have created drastic changes in a matter of minutes and hours, with effects lasting for a long period of time, thus eliminating the majority of the life. Massive volcanic eruptions, with the Siberian super-volcano being the prime candidate, may have caused enormous amounts of carbon dioxide and sulfur dioxide to end up in the atmosphere, thus rapidly changing the living conditions on the planet.
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