Gentle Slopes and Weathering.

 Weathering! Sediment Sources! Here is an article about looking at weathering and sources of sediment in the context of sequestering carbon.

"Most people, if they're geologists, thought mountains, and the uplift of mountains, were a really good way of sequestering [carbon dioxide] over a really long time scale," Willenbring said. "But in fact, where carbon sequestration happens is in these lowland rivers and places that are gently sloping," she told OurAmazingPlanet.

One of the ways carbon ends up in dirt is through chemical weathering, which occurs when rock turns into sediment. Carbon dioxide molecules and rain combine to dissolve rock, and the weathering products include sand, clay and other types of sediment. Physical weathering, such as from wind or glaciers, can also grind down rocks into dirt."