The Earth is a "closed system" which means that the amount of rocks, carbon, metals, nitrogen, water and oxygen on earth remains constant.
So it is essential that "biogeochemical cycles renew these materials" as they move through the Earth's subsystems.
<u>Explanation</u>:
The Earth's only source of extra-planetary energy is the Solar radiations received by Earth.
The biogeochemical cycles on the planet are responsible for processing the same old rocks, metals, carbon, nitrogen, oxygen, water, and other abiotic substances on Earth in order to naturally renew them and make them available for reuse.
No naturally occurring element on Earth is newly produced. It is only renewed through biogeochemical processes.
