. Elementary physical geography . e. Each par-ticle must depend upon the lifeand death of a tiny chalk of England, andother regions, is a rock whoseorigin was similar to that of theGlobigerina ooze. Med Clay.—At a depth great-er than 2000 or 2500 fathoms,the bottom ooze changes itscharacter and becomes known asred clay. This form of ocean deposit is particularly abun-dant in the Pacific, although it is not entirely absent fromthe Atlantic. It is one of the most remarkable depositsbeing made in the ocean. In these great ocean depths, thepower of the salt water to dissolve the lime of
. Elementary physical geography . e. Each par-ticle must depend upon the lifeand death of a tiny chalk of England, andother regions, is a rock whoseorigin was similar to that of theGlobigerina ooze. Med Clay.—At a depth great-er than 2000 or 2500 fathoms,the bottom ooze changes itscharacter and becomes known asred clay. This form of ocean deposit is particularly abun-dant in the Pacific, although it is not entirely absent fromthe Atlantic. It is one of the most remarkable depositsbeing made in the ocean. In these great ocean depths, thepower of the salt water to dissolve the lime of shells hasincreased until this substance is taken in solution as theshells drop from the surface. Therefore the insoluble por-tions, of which there are tiny amounts in every shell, are theonly parts of the Globigerina that reach the bottom. There-fore the ooze is in part a residue of the shell after thesoluble portions have been removed. And if the shells weresmall at the beginning, how much smaller must these tinyremnants be!. Fig. 78. Globigerina ooze from the ocean bottom. 166 PHYSICAL GEOGRAPHY. It is not exclusively made of the residue of the shellsof surface animals, but contains contributions from othersources. The most common addition comes from pumicerocks, which were ejected from volcanoes, and after floatingfor some time settled to the ocean bottom at some distantpoint. Therefore, remnants of volcanic ash or pumice arecommon in the red ooze. Aside from this, there are frag-ments of meteorites which have dropped to the bottom,indicating exceedingly slow accumulation. This depositcovers an area of over 51,000,000 square miles, which is alittle more than that covered by the Globigerina ooze. Eachkind of deposit covers an area equal to about one-fourth ofthe earths surface. Life in the Ocean: Pelagic or Surface Faunas. — Theocean is the great meeting ground of the life of threeprovinces, — the air, the land, and the water. Forms belong-ing to all the great groups
Size: 1292px × 1934px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthortarrralphsralphstockm, bookcentury1900, bookdecade1900
