Reading Comprehension (RC) | Until the 1950s, most scientists believed that the geology of the ocea

[align=justify][box_out][box_in] Until the 1950s, most scientists believed that the
geology of the ocean floor had remained essentially
unchanged for many millions of years. But this idea
became insupportable as new discoveries weremade.
(5) First, scientists noticed that the ocean floor exhibited
odd magnetic variations. Though unexpected, this was
not entirely surprising, because it was known that
basalt—the volcanic rock making up much of the
ocean floor—contains magnetite, a stronglymagnetic
(10) mineral
...

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