1.8 million years ago - 11,000 BC

Animate the Continental Drift

New Species:

  • Homo sapiens

Temperature drops
Glaciers expand south over the Earth
Hardwood forests begin to appear in temperate areas
Mammoths, mastodons, saber-tooth cats, giant ground sloths
was the
Bay like?

The Last Ice Age

The Ice Age began in the Pleistocene epoch, approximately 1.8 million years ago. During the Pleistocene, mountain glaciers formed on all the continents and vast glaciers, in places as much as several thousand feet thick, spread across North America and Eurasia. In the eastern U.S., the ice at one time penetrated as far south as central Pennsylvania and northern New Jersey.

Though we sometimes think of the " last ice age" as one long, cold period, it wasn't. Ice advanced and retreated as the Earth cycled between glacial (colder) and interglacial (warmer) periods. The ice advances and retreats in North America have been given different names (see chart at left). During the warmer, interglacial periods, debris of all sizes was released by the melting ice and was carried forward by melt-water streams or deposited near the ice margin. In many areas of the U.S., these deposits changed the shape of the continent and created the soil structure that exists today.

Archaeological information indicates that hominids evolved rapidly during this time period; our most primitive tools and skeletal remains date back to the Pleistocene. With the end of the Pleistocene, and the retreat of the giant ice sheets, our Bronze and Iron Age cultures developed. The retreat of the ice also had profound effects on the animals that had evolved during the glacial periods. Many of the animals suited to cooler climates became extinct, especially the large megafauna like the wooly mammoth, mastodon and saber-tooth tiger.

The Delaware Bay

Though it never reached the Delaware Peninsula, the advancing glaciers had profound effects. Each time the ice advanced, it incorporated so much water that the sea level dropped to as much as 500 feet below its present levels and the ice melt coming off the edge of the glaciers dug deep ravines into the earth. The ancient Delaware and Susquehanna Rivers flowed at the bottom of two of these ravines, some 200 feet below the level of the plain.

The Delaware Bay is an estuary formed from a drowned river valley. During glacial times, the river channel flowed along the bottom of the present-day bay. Because the glaciers stored much water in their ice, the ocean level was much lower then. When the glaciers melted, the river valley "drowned" and formed the estuary.