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).
Plate Tectonics. Plate Tectonics is a geologic theory explaining the movements and forces in the Earth crust. It was developed during the mid 20th century, but the basic ideas were first put into words by the German geologist Alfred Wegener during the 1920s.