In the last 4 million years, the Earth's magnetic north and south poles have switched places at least 11 times, the most recent flip happening about 780,000 years ago.
(the Earth's magnetic north and south poles; have switched; places; T:at least 11 times; T:In the last 4 million years) (the most recent flip; happening; T:about 780,000 years ago)
the Earth's magnetic north and south poles the most recent flip
have switched happening
places T:at least 11 times T:In the last 4 million years
T:about 780,000 years ago