Cretaceous hydrothermal-vent period

The Cretaceous hydrothermal-vent period marks the deep geological timescale behind the Trench’s hydrothermal megaplumes: the vents producing them are described as chronic and active since the Cretaceous period. The reference establishes their extraordinary duration, though the passage gives no more precise date for their beginning.

Reference in the Narrative

The period is introduced during an explanation of hydrothermal vents and the warm layer of water they sustain along the bottom of the Trench. The speaker calls the plumes chronic, then anchors that persistence to activity dating back to the Cretaceous period. The time reference makes the vents’ longevity part of the setting’s explanation rather than a separate historical episode.

Significance and Limits

By connecting present-day conditions in the Trench with activity extending back to the Cretaceous hydrothermal-vent period, the account presents the vent system as a persistent feature of the environment. It does not specify when within the period the vents became active, how their activity changed over time, or give a numerical duration.