For contrast, review the population pyramids for India by selecting the years 1970 and 2015. Compare these pyramids to those of China for the same years. What differences can you see?

Why is the huronian supergroup rock formation particularly interesting to scientists? because it looks like a cross-section of a giant, stone encyclopedia because it formed during the period when oxygen began to accumulate in the atmosphere because it contains unusually large amounts of oxygen and sulfur because it dramatically altered the planet's development when it first formed