A scientist is studying the moist, sandy soil on a particular floodplain along a river in the Post Oak Savanah ecoregion of Texas. The soil is an important part of a habitat that supports many plants and animals. The materials that make up the soil are similar to the materials in rocks upstream and different than the bedrock in the floodplain. How did this floodplain form?
A.
Environmentalists built the floodplain from coastal beach sands.
B.
The floodplain formed from a lava flow during a volcanic eruption.
C.
The river deposited sediment outside of its banks during times of flooding.
D.
A massive flood eroded a mountain until it was a flat plain.