Assertion: mass extinction | /r/AtLocation | earth
Facets:
value: in the known past
type: TEMPORAL
Source sentences:
text: The deifnition of 'significant' varies depending on the authority, and hence anywhere from five to over twenty mass extinctions have occurred on Earth in the known past - it is probable that more have happened, but this cannot be discerned from fossil and other records because of the size of the organisms involved.