Quizlet is a great flashcard site that helps you create your own flashcards, and provides you with some great ready-made flashcards as well. As an ESL teacher, I find it to be very useful, especially for students who are not native speakers and do not have anybody at home to help them with their vocabulary.
The atmosphere, the ocean, and the terrestrial biosphere. Carbon can be found in the earths oceanic and continental crust in different types of stones as well as in the soil from the decay of organic matter.
Biogeochemistry includes the history of the great carbon reservoirs in the crust of the Earth, like limestone rocks and the coal deposits, as well as the distribution of nitrate and phosphate in the ocean.