Fossil fuels are often described as non-renewable energy sources.
what are they called 'non-renewable'?

Non-renewable energy comes from sources that will run out or will not be replenished for thousands or even millions of years. Most sources of non-renewable energy are fossil fuels. Fossil fuels were created as the remains of marine creatures decayed millions of years ago, under huge amounts of pressure and heat.

Explanation:

the oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf, but operationally is often referred to as beginning where the water depths drop to below 100 meters (328 feet), seaward from the coast to the open ocean.

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