When glaciers scrape across Antarctica, they pick up rock fragments and incorporate them into their bottom layers while transporting them toward the coast. There, icebergs break off, drifting towards lower latitudes and warmer waters. Along the way the icebergs melt and the rock fragments sink to the seafloor, leaving behind a trail of these rock fragments called ice rafted debris. Ice rafted debris accumulates at the bottom of the ocean and over time preserves a record of activity at their source, the Antarctic ice sheet. In this study investigators will use sediment cores recovered in the Indian Ocean by the Ocean Drilling Program to reconstruct the accumulation of ice rafted debris over time. The drill site is about 500 miles north of the Antarctic continent, and in the path of the ice bergs that it sheds. When looking at the variations in ice rafted debris over time, the team will obtain a record of changes in the glacial activity of the Antarctic ice sheet through time. The study is motivated by the mystery surrounding changes in glacial activity in response to changes in the shape of Earth’s orbit around the sun, the wobble of its axis, and the degree of the tilt of the Earth’s axis, the so-called Milankovitch cycles. For a period of time between about 1.2 and 1.6 million years ago, it is not clear if ice sheet growth and melt responded to changes in incoming solar energy related to changes in the shape of the orbit or to changes in its tilt toward or away from the sun.