If a substance has a half-life of 10 million years, what fraction of the atoms

remain after 20 million years?

Burning fossil fuels and wood increases the amount of (what) in the atmosphere.

Describe the factors that control the rate of chemical weathering and those that control the rate of physical weathering

Why is salt water important to life on earth?

Which of the following climate regions has the widest temperature range? a. arctic c. marine west coast b. subarctic d. tropical

What is the primary cause of acid rain? a. deforestation b. fossil fuel emissions c. overgrazing d. nuclear disasters

How was the Great Leap Forward supposed to increase China's production? A. by replacing private ownership of farms with common ownership B. by combining China's collectives into self-sufficient People's Communes C.

Oil and natural gas result from

A sphere made of steel is put in water and, surprisingly, it floats. Develop a hypothesis to explain this observation.

What is the primary economic activity of the outback is

Which African country faced a serious genocide in 1994, during which almost one million people were killed? A. Rwanda B. Zaire C. the Democratic Republic of the Congo D.