Complex sentence: Offshore drilling on the US Atlantic coast for oil and gas took place in the late 1970s and early 1980s oil companies drilled 51 exploratory wells on federal leases on the outer continental shelf of the Atlantic coast.
Split into simpler sentences: Offshore drilling on the US Atlantic coast for oil and gas took place in the late 1970s and early 1980s. Oil companies drilled 51 exploratory wells on federal leases on the outer continental shelf of the Atlantic coast.