Why are desert landscapes jagged and rocky?

What are the similarities and differences in the way geologists and biologists approximate the age of the earth? justify your response in two or more complete sentences.

17. the soil erosion pictured here is the result of what? a. harvesting renewable resources at a rate greater than the sustainable yield b. a mudslide caused by excessive rains c. harvesting renewable resources at a rate lower than the sustainable yield d. the transition between geologic eras and eons

During which era in earth's history were the first insects? mesozoic precambrian cenozoic paleozoic