which is NOT a type of biogenous sediment

You observe a string of islands on topographical map. The islands have an arc-like appearance, but are not in a location along lithospheric plate boundaries. What geologic force gave rise to these islands?

Hydrothermal vents are found in locations where the sea floor spreads (divergent plate boundaries). Here, seawater seeps into cracks in the oceanic crust and is heated by the mantle, and ejected from the vents. The "black" color of some hydrothermal vents are due to high concentrations of ______ that precipitate to build chimneys around the vents.

At this time in the earth's history, sea levels were 130 m lower than they are today, and most recent glacial period was at its peak. When was this?,,