Answer to Question 1
Terrigenous derived from land sediment consists primarily of mineral grains that were weathered from continental rocks and transported to the ocean, such as example, the abyssal clay layer that forms in the deep ocean. Biogenous derived from organisms sediment consists of shells and skeletons of marine animals and algae; the most common biogenous sediment is calcareous ooze. Hydrogenous derived from water sediment consists of minerals that crystallize directly from seawater through various chemical reactions, such as manganese nodules, which are rounded, hard lumps of manganese, iron, and other metals that precipitate in concentric layers around a central object.
Answer to Question 2
Most seafloor sediments contain the remains of organisms that once lived near the sea surface. When such near-surface organisms die, their shells slowly settle to the floor of the ocean, where they become part of the sedimentary record. These seafloor sediments are useful recorders of worldwide climate change because the numbers and types of organisms living near the sea surface change with the climate. One notable example of the importance of seafloor sediments to our understanding of climate change relates to unraveling the fluctuating atmospheric conditions of the Ice Age.
