Oceanography is is the study of the physical and biological aspects of the ocean, so my assumption is an oceanographer is a person who studies those things.
B rift valley
Explanation:
Divergent boundaries within continents initially produce rifts, which eventually become rift valleys. Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges.
Alluvial soil is fine-grained sediment usually deposited by flowing water. As for why farmers like it, my guess is because it's so fertile. It's fertile because of all the varied particles contained in it, which includes animal waste and decomposing matter. Crops grow better in it.
A giant elliptical can contain 400 billion of stars
