As sediments are transported from mountains toward shorelines, how do grain size, sorting, and mineral variety typically change?

As sediments are transported from mountains toward shorelines, how do grain size, sorting, and mineral variety typically change?

• A. Grains become smaller and better sorted and more rounded; mineral variety decreases
• B. Grains become larger and more angular; mineral variety increases
• C. Grains stay the same size; sorting worsens
• D. Grains dissolve completely

Answer: (A)

As sediments move from mountains toward the coast, they undergo abrasion and selective deposition that break them down and smooth rough edges. This transport also tends to reduce the size of the grains, because continual grinding wears them down. At the same time, the energy of the transporting environment changes along the journey; as the sediment load slows and the current weakens, sorting improves—the deposit ends up with grains more similar in size because larger grains settle out earlier and finer grains settle later, narrowing the size range. Chemical and physical weathering during transport also wears away less stable minerals, leaving a more durable, common set of minerals like quartz. That reduces the variety of minerals present in the sediment. So, overall, grains become smaller and more rounded, sorting becomes better, and mineral variety decreases as sediments travel toward shore.

As sediments move from mountains toward the coast, they undergo abrasion and selective deposition that break them down and smooth rough edges. This transport also tends to reduce the size of the grains, because continual grinding wears them down. At the same time, the energy of the transporting environment changes along the journey; as the sediment load slows and the current weakens, sorting improves—the deposit ends up with grains more similar in size because larger grains settle out earlier and finer grains settle later, narrowing the size range.

Chemical and physical weathering during transport also wears away less stable minerals, leaving a more durable, common set of minerals like quartz. That reduces the variety of minerals present in the sediment.

So, overall, grains become smaller and more rounded, sorting becomes better, and mineral variety decreases as sediments travel toward shore.