Most ozone (about 90%) is found in the stratosphere, which begins about 10–16 kilometers (6–10 miles) above Earth's surface and extends up to about 50 kilo- meters (31 miles) altitude.
In Literature, Subject is referred as a topic. The theme is the opinion expressed on the subject. So basically, both are entirely different. Hope this answers your question.
The theme of American History by Judith Ortiz Cofer are cultural isolation signified in Elena's difficulty with living in Patterson, New Jersey and how the attitudes of people around her affect her feelings about herself and the world.