What is the current greatest threat to agricultural sustainability? a. erosion b. water pollution c. air quality d. all of the above

Correct A). Erosion

The greatest threat to agricultural sustainability can be caused due to erosion. Erosion is a natural phenomenon that is known to affect all landforms. In agricultural practice, soil erosion is a process that is known to remove the top fertile layer of the soil, that may be caused by natural or physical agents like wind, water etc. It may also be caused by some form of farming practice such as tillage.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

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