Which theory states that floods and earthquakes have occurred often in Earth's history?

Catastrophism.

Explanation:

Catastrophism is a theory which states that floods and earthquakes have occurred often in Earth's history.

Baron Georges Cuvier who was a French anatomist developed catastrophism based on a collection of paleontological evidences he found in the Paris basin.

For example, catastrophism may postulate that all Rocky mountains were created by an earthquake, which in itself is a singular and rapid event rather than a gradual event that causes slow uplift and erosion.

hi~~

i would say that hybridization occurs frequently in nature, because there are many types of hybrids that have occurred naturally, such as the mule (male donkey + female horse)

substitution is the answer in this case