Which layer of the earth's atmosphere contains the largest percentage of ozone?

Explain why the rate of urbanisation is in the way it is between developed and undeveloped countries.

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

The magnitude of an earthquake is typically calculated according to the scale.           a. mercalli   b. fujita   c. richter   d. saffir-simpson