The section is the soil deposited and heap as muck near the estuary and the sprout are the land continue.
This portion is hard and resistant to corrosion than it sank and accumulate as sand in the sea. Some are borne by the waves into shore, more a concept of accumulated sand common along the coast.
Sand on the beach, so is the rest of the weathering of the stones that are often composed of quartz (Quartz) with strength and resistance to corrosion, high.