1700 Cascadia earthquake in the context of "Pacific Time Zone"

A paleotsunami is a tsunami that occurs prior to written history where there are no documented observations. Paleotsunamis are evidenced by modern technology and scientific research. One of the largest was a megatsunami resulting from the asteroid that wiped out the dinosaurs.

Studying paleotsunamis is an emerging science to identify and interpret paleotsunami deposits. There are several recorded paleotsunami records, though some are known only by historical mentions, such as tsunamis resulting from the 1700 Cascadia earthquake which is known only from oral traditions among the Native Americans of the Pacific Northwest and simultaneous Japanese accounts of the same event.

Paleoseismology is the study of ancient earthquakes using geologic evidence, such as geologic sediments and rocks. It is used to supplement seismic monitoring to calculate seismic hazard. Paleoseismology is usually restricted to geologic regimes that have undergone continuous sediment creation for the last few thousand years, such as swamps, lakes, river beds and shorelines.