What is a type of fee simple defeasible estate that automatically reverts upon the violation of deed requirements?

The type of fee simple defeasible estate that automatically reverts upon the violation of deed requirements is the fee simple determinable. This estate is unique because it is conditioned on a specific event or purpose. If that specified condition is violated or fails to occur, the property automatically returns to the original grantor or their heirs without the need for legal action. This automatic reversion is what distinguishes a fee simple determinable from other types of estates.

In contrast, a fee simple absolute represents full ownership without any conditions and does not lead to reversion or loss based on specific actions or circumstances. A fee simple conditional, on the other hand, also has conditions that, if violated, may lead to reversion, but this reversion typically requires legal action rather than occurring automatically. Lastly, fee simple reversionary is not a widely recognized term in the context of estate interests; rather, the concept generally relates to the reversion aspect found in conditional interests.

Thus, the defining characteristic of a fee simple determinable is its automatic reversion mechanism upon the breach of the deed's terms, making it the correct answer.