The Mississippi River today is a classic meandering river. 20,000 years ago the Mississippi River was a major outwash channel for the Laurentide ice sheet, and was characterized by dramatic variations in flow with huge discharge during summer ice
melt and a dramatic falloff in discharge during the winter. The river also carried coarser sediment than today, with abundant sand and even gravel in its upper reaches. What does this suggest about the ancient Mississippi?
A) It probably resembled modern rivers in Alaska with a broad braided stream valley that dried up during the winter months, producing winter dust storms.
B) It was probably a lush heavily vegetated valley due to the nutrients brought down by the glacial meltwater, producing a swampy landscape with numerous channels.
C) It probably looked similar to the river today, but was characterized by more dramatic summer floods that occurred every year.
D) It is impossible to predict what the river might have looked like.
A
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