Glaciers spread across North America. They covered the land as far south as the Ohio River. The glaciers scraped and scoured the land as they pushed soil and rock ahead of them, creating the rich layers of till that cover the Midwest today. As Earth warmed and the glaciers melted, changes occurred in Earth's Landscape. Deep gouges and gullies made by glaciers filled with water, creating lakes and streams. New rivers were formed and began to shape the landscape. In some places, such as the east coast of the United States, a series of almost parallel rivers spurt a line of waterfalls.