Final answer:
New Orleans is built on soft sand, silt, and clay, which are substrates capable of forming load casts due to variations in sediment density and water saturation. The correct option is D.
Step-by-step explanation:
New Orleans is built on a combination of geological substrates. The most accurate answer to the question is D) All Above: Soft Sand, Silt, and Clay.
The unique geology plays a significant role in the challenges that New Orleans faces, especially in relation to flooding and infrastructure. The presence of load casts, which are bulb-like impressions created when dense sandy sediment is deposited on top of less dense, water-saturated silt or clay, indicates the composite nature of the ground beneath New Orleans.
Load casts form specifically because of the differing densities and the water-saturation of the lower layers, characteristics that are indicative of the sediments New Orleans is built upon.