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beds. While molten, the moving salt deformed the horizontal beds.
Later, the salt cooled and solidified and some of the deformed beds
trapped oil and gas. Spindletop was deformed by a piercement dome.
FINDING PETROLEUM TRAPS

In the early days of oil exploration, wildcatters (those who drill
wildcat wells, which are wells drilled where no oil or gas is known to
exist) often drilled in an area because of a hunch. They had no idea
how oil and gas occurred and probably didn’t care. Anybody with
enough money to back up a belief that oil lay under the ground at
some location or the other drilled a well. If they were lucky, they had
a strike. If not, it was on to the next hunch.
Soon, however, geologists began applying earth science to the
search for oil. For example, they looked for features on the surface
that indicated subsurface traps. One site was at Spindletop. An
underlying salt dome created a hill, or a knoll. The knoll seemed out
of place on the surrounding coastal prairie and led people like Patillo
Higgins and Anthony Lucas to drill for oil.
Most petroleum deposits lie so deeply buried, however, that no
surface features hint at their presence. In many places – West Texas is
one example –nothing but flat, mostly featureless land stretches for
many miles or kilometres. Yet, the subsurface holds large quantities of
oil and gas. Consider also that much of the world's oil and gas
probably lies offshore, covered by hundreds or thousands of feet or
metres of water and more thousands of feet or metres of rock.
Fortunately, scientists have developed effective indirect methods to
view the subsurface. They use seismology the most.
Seismology is the study of sound waves that bounce off buried
rock layers. Oil explorationists, or geophysicists, create a low-
frequency sound on the ground or in the water. The sound can be an
explosion or a vibration. If the oil hunters use explosions, the
explosions create sound waves that enter the rock. If they use
vibrations, a special truck forces a heavy weight against the surface

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