- Sedimentary rock (Wikipedia)
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth’s surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus (organic matter). The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus was formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies (marine snow). Sedimentation may also occur as dissolved minerals precipitate from water solution.
- Riverworld (Wikipedia)
The Riverworld is a fictional planet and the setting for a series of five science fiction novels (1971–1983) by American author Philip José Farmer (1918–2009). The Riverworld is an artificial, or heavily terraformed, planet where all humans (and pre-humans) who ever lived throughout history have been restored to life. The novels (and a few shorter works) explore interactions of resurrected individuals from many different cultures and time periods. The underlying theme is quasi-religious. The motivations and ethics of the unknown intelligences that created the Riverworld and its inhabitants are explored.