Earthquakes seemed to outline a special feature of earth's crust. Earthquakes let scientists know where the crust was moving. This led to the discovery that the Earths crust was broken up into regions, or plates. Earthquakes happen most often along these plate boundaries. This was evidence that continents can move. The movements of the plates are called plate tectonics. The Earths crust is divided into plates. There are about a dozen large plates and several small ones. Each plate is named for the continent or ocean basin it contains. Scientists know he plates are in motion. They now know the direction and speed of this motion . Plates dont move very fast. They move only a few centimeters a year. This is about the same rate fingernails grow. So you might wonder, what could cause this motion? What supplies the energy to cause this change?

How did scientists learn about the Earth's plates?

Elettra stuck the little slip of paper, on which the recipe was written, into her shabby pocket-book without looking at it. She could read and write fairly well, and had been used to helping her husband the under-steward with his accounts at Muro, but even if she had looked at the recipe she would have understood nothing of the doctor's hieroglyphics and abbreviated Latin words. The prescription was for a preparation of arsenic, which Matilde had formerly taken for some time. The chemist would not make any difficulty about preparing twenty doses of it for the Countess Macomer, though the whole quantity of arsenic contained in so many would probably be sufficient to kill one not accustomed to the medicine, if taken all at once. But though Matilde was so anxious to have the stuff before luncheon, she had a number of doses of it put away in a drawer, which she took out and counted, after Elettra had gone. She opened one of the little folded papers and looked at the fine white powder it contained, took a little on the end of her finger and tasted it. Then, from the same drawer, she took a package done up in coarser paper, and opened it likewise, looked at it, smelt it, and touched it with the tip of her tongue very cautiously indeed. It was white, too, but coarser than the medicine. She was very careful in tasting it, and she immediately rinsed her mouth with water, before she tied up the package again, shut the drawer, and put the key into her pocket.

What color was the arsenic?

Breathing is the process of moving air into and out of the lungs. The process depends on a muscle called the diaphragm. This is a large, sheet-like muscle below the lungs. Inhaling, or breathing in, occurs when the diaphragm muscle tightens. This increases the size of the chest. This too decreases air pressure inside the lungs. This action allows air and gases to enter the lungs. Exhaling, or breathing out, occurs when the diaphragm muscle relaxes. This decreases the size of the chest. This increases air pressure inside the lungs. This action allows for air to leave the lungs. When you inhale, air enters the respiratory system through your nose and ends up in your lungs, where gas exchange with the blood takes place. What happens to the air along the way? In the nose, mucus and hairs trap any dust or other particles in the air. The air is also warmed and moistened. Next, air passes through a passageway that is connected to the windpipe. The air then finds its way to the lungs. In the chest, the windpipe splits so that air enters both the right and left lung.
What happens to the size of the chest when the diaphragm muscle tightens?