1 They could be symptoms of cancer of the lung, head, and neck. 2  Anyone with a cough that lasts more than a month or with blood in the mucus that is coughed up should see a doctor. 3  A change in bowel habits. 4  Most changes in bowel habits are related to your diet and fluid intake.
The theory of plate tectonics is a relatively new scientific concept. While its forerunnerâthe theory of. continental driftâhad its inception as early as the late 16th century, plate tectonics only emerged and. matured as a widely accepted theory since the 1960s (see This Dynamic Earth booklet).
Jupiterimages/Photos.com/Getty Images. The theory of plate tectonics is a part of geology, which is the study of the earth and how it changes. Developed in the 1960s and 1970s, this theory states that the earthâs outer crust is made up of plates of rock that shift all over the globe.