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away exposed surfaces. Waters, supplied with humic acids from
vegetable decay, complete the disintegration, and what were solid
rocks become clay and sand. Rain and rivulets wash away this soil,
deliver the mud to the creeks, the creeks deliver it to the rivers, and
the rivers carry it to the sea where waves and tides spread it out
over the floor of the ocean.

Crustal movements

The earth's surface is not static or stable; great segments of it
are slowly raising, other great segments are slowly sinking.
Despite many theories, we know little of the causes of these crustal
movements. Whatever maybe the cause, the earth’s crust moves.
Volcanic eruptions are a result not a cause of mountain uplifts.

Rocks formed beneath the sea

What happens to the great masses of sediments that are
carried into the sea? When the streams that carry them enter the
quieter waters of the sea, the currents of the streams are checked
and begin to drop their load. The coarser sediments such as gravel
and sand are dropped first; the muds settle farther out in quieter
waters; the lime and other soluble materials are slowly precipitated
still farther out or become the shells and skeletal structures of
myriads of minute organisms, and sink to the bottom as these
myriads die. The waves play an important part, especially near the
shore. They distribute the sand along the coast and move the finer
sediments out to deeper waters.
As the sediments pile up to thickness of thousands of feet,
those at the bottom are weighed down by those above; much of the
water is squeezed out and compaction into rocks begins. Then
sometimes, when a crustal movement starts and what was seafloor
gradually becomes upland, the sediments are subjected to great
and shifting pressures through hundreds of thousands of years.

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