In the last Ice Age, the Wisconsin Glacier extended across Canada and as far down as North Jersey. As the glacier receded, rivers carried the melting waters out to sea. In fact, the oceans were far lower at that time because so much water was locked in the ice, so much so that fishing trawlers working off the coast of the New Jersey we know today have found Mastodon bones hundreds of miles out from the present shoreline.
Scientists believe that the Mastodon bones discovered in Lenape Park, not far from the Rahway River, washed down to that location from Mastodons that were roaming further north, closer to the glacier.
To get a sense of what the Wisconsin glacier that would have looked like as it began to recede, click the video below. Also, feel free to explore the USGS website, where there are several other videos.
South Cascade Glacier is one of three benchmark glaciers studied by the USGS for the effects of changes in climate. The mass-balance scientific record for South Cascade Glacier is the longest of its kind in North America and is used by climate scientists worldwide.