The Pleistocene climate was marked by repeated glacial cycles.

Geological records of glacial cycles have been largely destroyed on land by the action of glaciers.

These orbital changes, however, have been going on for far longer than recent glacial cycles.

Over the past 740,000 years there have been eight glacial cycles.

It reached back 420,000 years and revealed 4 past glacial cycles.

Until about a million years ago, the alternating glacial and interglacial cycles were of roughly even duration.

The core goes back 740,000 years and reveals 8 previous glacial cycles.

The rerouting of ocean currents led to climatic changes as the Earth entered a glacial cycle.

The most significant climate processes since the middle to late Pliocene (approximately 3 million years ago) are the glacial and interglacial cycles.

Hundreds of similar glacial cycles have occurred throughout the Earth's history.