Why are no rocks found that date from the first 800 million years of earth's existence?

Gold is not now being extracted from seawater. why not? a. it would be too disruptive to marine life to develop any marine mineral resources b. there is no gold in seawater c. we don't know how to extract minerals from seawater d. it would be too costly and difficult to separate the small amount of gold from the very large amounts of halite and other minerals

The primary agent of contact metamorphism is

According to a recent survey, the local government wants to classify people according to their income earning capacity. they want to do so in order to provide special facilities for the poor. who among the four individuals will be classified as poor? a. joseph earns $2.25 per day b. maria earns $1.50 per day c. rosita earns $2.00 per day d. tim earns $ 1.00 per day