A continuous cycle of elements passing through and between the Earth’s lithosphere, biosphere, hydrosphere, and atmosphere. For example, sodium is released from rocks (lithosphere) by weathering and is transported in solution or suspension to the sea (hydrosphere). Sediments formed in the oceans take up sodium and may be compacted to join the geologic cycle, becoming sedimentary, metamorphic, and perhaps ultimately new igneous rock. See biogeochemical cycle.