The ice lobe that formed the statewide trough of the Minnesota River was the last of several that entered Minnesota during the last period of glaciation. Ice lobes were dynamic tongues of ice that extended far south of the main ice sheet and in contrast to the glacial ice sheet that moved slowly, ice lobes advanced quickly and then stopped. Elaborate on how such an ice lobe may be responsible for the formation of the Minnesota River. A) The ice lobes advanced and stopped many times, eroding the land to create a trough and then filled it with draining water from the ice sheet that was feeding them.
B) There was no true drainage valley for the melting glaciers and multiple small streams flowed from north to south. Eventually they merged, forming the Minnesota River.
C) Beneath the till of the Des Moines ice lobe lie layers of older glacial units from previous glaciations; these layers vary in thickness and when they melted, formed the Minnesota River.
D) Outwash plains contained large amounts of glacial till that eroded the land and one area was the trough of the Minnesota River. Eventually the waters of the outwash plain filled the trough.