The glacial record on land is punctuated by many erosional gaps. This makes it difficult to reconstruct the episodes of the Ice Age, But sediment on the ocean floor provides an uninterrupted
record of climate cycles for this period. Studies of cores drilled hom these seafloor sediments show that glacial/interglacial cycles have occurred about every 100,000 years. Approximately 20 such cycles of cooling and warming were identified for the span we call the Ice Age.