Longshore drifts and waves

The radius of these paths

_________ with depth until, at a distance below the surface equal to 1half a wavelength, water remains stationary

• decreases

• increases

In the open ocean, the wave base, the _______level at which water moves in a wave, lies far above the seafloor, so wave motion has _____ effect on the ocean floor.

• Low; zero

• high; a large

• Low; a large

• High; zero

Nearer shore, however, where the wave base just touches the ocean floor, a passing wave causes a slight back-and-forth motion of _______.

• wind

• sediment

• waves

The toppling water at the crest of a breaker mixes with air to form a _____________

• bubbles

• brown froth

• white froth

• large waves

This upward surge, or swash, continues until friction and gravity bring water motion to a halt. Then gravity draws the water _______ the beach as backwash.

• backwards

• upwards

The crests of waves that make an angle to the shoreline bend as they approach the shore, a phenomenon called wave ___________

• backwash

• toppe

• diffration

• refraction

Typically, by the time the wave reaches the shore, the angle between the crest and the shoreline decreases to less than ____°

• 20

• 10

• 5

• 1/2

This longshore current causes swimmers floating in the water just offshore to drift gradually in a direction ________ to the shoreline

• Perpendicular

• parallel

Storm waves can smash cobbles against one another with

enough force to shatter them, but they have _______ effect on sand.

• a large

• no

Sands derived from the weathering and erosion of felsic to intermediate rocks consist mainly of quartz, a ______ mineral.

• durable

• brittle