30 The Sea 
mals with calcareous (chalky) shells form globigerina and 
pteropod oozes. Globigerina have spherical shells and thou- 
sands of tiny hairlike appendages which make them appear 
like Christmas tree decorations. The ooze they form is the 
principal constituent of the floor of the Atlantic Ocean and 
covers large areas in other oceans as well. Globigerina ooze 
covers as large an area of the ocean floor as the area of all the 
dry land of the world. | 
Pteropods are little swimming snails commonly called “sea 
butterflies.” Pteropod ooze is less abundant than other va- 
rieties of ooze, is found in shallower water than globigerina 
and is generally located near the Equator. 
The deepest parts of the ocean are not covered with ooze 
because in passing through such great extents of ocean water 
all the tiny skeletons and shells are completely dissolved. One 
substance that can survive the long trip down is volcanic 
dust, shot up into the atmosphere by a volcanic eruption, 
and later settling into the sea. Wind-blown dust from the 
world’s great deserts also finds its way to the ocean floor. It 
collects in the abyssal regions to form a red clay. Thus the 
deeper parts of the ocean—particularly in the Pacific Ocean 
—are floored with a true red clay. The rate at which the sedi- 
ments under the open sea form is extremely slow—less than 
one-half inch in a thousand years. | 
GLOBAL JUNKYARD 
The depths of the ocean act as a kind of junk heap for 
other things as well. The oceanographer is not much sur- 
prised to find side by side in one haul the tooth of a pre- 
historic shark, cinders dropped from a steamer long ago, a 
piece of meteoric iron from outer space, perhaps stones and 
