Final answer:
Over the past 700,000 years, there have been roughly 11 major glacial cycles, with multiple glacial periods within each cycle. The most recent glacial period began over 100,000 years ago and ended around 12,000 years ago.
Step-by-step explanation:
Over the last 700000 years, Earth has experienced several cycles of cooling and warming. Scientists have identified at least five significant ice ages in Earth's distant past, each containing multiple glacial periods. Records show that during the most recent 700,000 years, there have been approximately 11 major glacial cycles, with the latest major glacial period beginning over 100,000 years ago and peaking around 18,000 years ago. This last period was part of an ice age that ended about 12,000 years ago, during which ice sheets up to two miles thick covered vast areas of the Northern Hemisphere.