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 theoretical model builds on the concept of continental drift developed during the first few decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s and early 1960s. The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken up into tectonic plates.
Acceptance that large crustal motions were a reality soon followed, culminating in the theory of plate tectonics. In its slow convergence of ideas and evidence, the history of plate tectonics holds lessons for today's debates about human-induced climate change.