Midterm 1: short answer1.Using the “rule of 70”, a population growth rate of 2% would lead to a doubling of the world’s population in 35 years. 2.Since 1900, the world’s human population has been increasing at an annual rate between 0.5 and 2.5%.3.The present Earth’s atmosphere is mostly made of nitrogen and oxygen. 4.The Earth’s lithosphere is broken into how many rigid plates? 145.Relative to the age of the Earth, the fraction of time that humans have existed is 0.04%.6.The Wilson Cycle includes rifting-subduction-collision7.Ocean island “tracks” such as that of Hawaii and the Emperor Seamount Chain: indicate plate motion opposite to the direction of “younging” of the volcanic islands and seamounts. 8.The asthenosphere is the principle cause of plate tectonics on Earth. 9.Rocks older than 4.0 billion years have not been found on Earth because the initial plates contained mostly basaltic crust which was recycled back into the mantle.
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