Engineers will often build breakwaters and (*)  jetties to prevent the movement of this substance, which is often accumulated onto a namesake "spit" through longshore drift.
"Revolving rivers" are formed by depositing this solid material onto a base that undergoes rotation. "Hard stabilization" techniques are designed to prevent the movement of this material; such techniques include using large rocks to build groins that run parallel to each other. A ridge of this material comprises a tombolo, which connects an island to the mainland. Engineers will often build breakwaters and (*)  jetties to prevent the movement of this substance, which is often accumulated onto a namesake "spit" through longshore drift. Technically, this term refers to a material whose grain size is finer than a pebble, but is coarser than silt. Particles of this substance are comprised of mostly silicon dioxide. For 10 points, name this substance often found at beaches.
"Revolving rivers" are formed by depositing this solid material onto a base that undergoes rotation.
sand