How Does a Sudden, Massive Increase in Hash Rate Affect the Immediate Block Discovery Time?

A sudden, massive increase in hash rate will immediately decrease the time it takes to discover a new block, making the block interval shorter than the target (e.g. less than 10 minutes). This is because the difficulty has not yet adjusted to the new, higher hash rate.

The difficulty will only adjust two weeks later to compensate.

How Does the Difficulty Adjustment Mechanism Affect the Attack Cost over Time?
Why Is a Double Hash Used in Bitcoin Addresses Instead of a Single Hash?
What Is the Relationship between Network Hash Rate and Mining Difficulty Adjustments?
How Does a “Hash Rate” Differ from “Network Difficulty”?
What Would Happen If the Bitcoin Network Difficulty Never Adjusted?
How Is the “Target Hash” Calculated from the Difficulty Setting?
How Does the Time-to-Block-Discovery Relate to the Network’s Difficulty Target?
Does the Pool’s Hash Rate Influence the Difficulty of the Individual Work Assigned to Miners?

Glossar