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Sand Movement on the Beach
Wave Erosion
Shorelines
Wave Erosion
During calm weather wave action is minimal. However, just as streams do most of their
work during floods, so too do waves perform most of their work during storms. The impact
of high, storm-induced waves against the shore can be awesome (FIGURE 13.8). Each breaking wave may hurl thousands of tons of water against the land, sometimes making the
ground tremble. The pressures exerted by Atlantic waves in wintertime, for example,
average nearly 10,000 kilograms per square meter (more than 2000 pounds per square
foot). The force during storms is even greater.
It is no wonder that cracks and crevices are quickly opened in cliffs, coastal structures,
and anything else that is subjected to these enormous shocks. Water is forced into every
opening, greatly compressing air trapped in the cracks. When the wave subsides, the air
expands rapidly, dislodging rock fragments and enlarging and extending fractures.
In addition to the erosion caused by wave impact and pressure, abrasion, the sawing
and grinding action of water armed with rock fragments, is also important. In fact, abrasion
is probably more intense in the surf zone than in any other environment. Smooth, rounded
stones and pebbles along the shore are obvious reminders of the grinding action of rock
GEODe
ESSENTIALS
OF GEOLOGY
against rock in the surf zone (FIGURE 13.9A).
Further, such fragments are used as tools
by the waves as they cut horizontally into
the land (FIGURE 13.9B).
C O N C E P T C H E C K 1 3 . 4
Describe two ways in which waves cause
erosion.
Sand Movement
on the Beach
Beaches are sometimes called “rivers of
sand.” The reason is that the energy from
breaking waves often causes large quantities of sand to move along the beach face
and in the surf zone roughly parallel to the
1
FIGURE 13.8 When waves break against the shore, the force of the water can be powerful and the
erosional work that is accomplished can be great. These storm waves are breaking along the coast of
Wales. (The Photo Library Wales/Alamy)
Sand Movement on the Beach
Wave Erosion
Shorelines
Wave Erosion
During calm weather wave action is minimal. However, just as streams do most of their
work during floods, so too do waves perform most of their work during storms. The impact
of high, storm-induced waves against the shore can be awesome (FIGURE 13.8). Each breaking wave may hurl thousands of tons of water against the land, sometimes making the
ground tremble. The pressures exerted by Atlantic waves in wintertime, for example,
average nearly 10,000 kilograms per square meter (more than 2000 pounds per square
foot). The force during storms is even greater.
It is no wonder that cracks and crevices are quickly opened in cliffs, coastal structures,
and anything else that is subjected to these enormous shocks. Water is forced into every
opening, greatly compressing air trapped in the cracks. When the wave subsides, the air
expands rapidly, dislodging rock fragments and enlarging and extending fractures.
In addition to the erosion caused by wave impact and pressure, abrasion, the sawing
and grinding action of water armed with rock fragments, is also important. In fact, abrasion
is probably more intense in the surf zone than in any other environment. Smooth, rounded
stones and pebbles along the shore are obvious reminders of the grinding action of rock
GEODe
ESSENTIALS
OF GEOLOGY
against rock in the surf zone (FIGURE 13.9A).
Further, such fragments are used as tools
by the waves as they cut horizontally into
the land (FIGURE 13.9B).
C O N C E P T C H E C K 1 3 . 4
Describe two ways in which waves cause
erosion.
Sand Movement
on the Beach
Beaches are sometimes called “rivers of
sand.” The reason is that the energy from
breaking waves often causes large quantities of sand to move along the beach face
and in the surf zone roughly parallel to the
1
FIGURE 13.8 When waves break against the shore, the force of the water can be powerful and the
erosional work that is accomplished can be great. These storm waves are breaking along the coast of
Wales. (The Photo Library Wales/Alamy)