What type of load consists of earth material dissolved into ions and carried in solution?

The correct answer identifies dissolved load as the type of load that consists of earth material that is fully dissolved into ions and carried in solution by a stream or river. This process typically involves the chemical weathering of rocks and minerals, where water interacts with these materials, breaking them down and resulting in soluble ions. These ions, such as calcium, sodium, potassium, bicarbonate, and others, are then transported within the water column, making them a crucial component of the stream's chemistry.

This contrasts with other types of loads. Bed load refers to larger particles, such as sand and gravel, that roll or slide along the bottom of a water body, while suspended load consists of fine particles like silt and clay that are held in suspension within the water column, making them visible as murky water. Transported load is a more general term that can describe all materials moved by a stream, but it does not specifically address the dissolved state of the materials. Therefore, dissolved load is the precise term used to articulate the presence of dissolved minerals and ions in water.