Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 69

At the center of the earth is its core. Scientists have not been able to sample it directly, but based on their laboratory experiments and interpretations, they believe the core is composed of massive, heavy metal elements such as nickel and iron. The core itself has two layers:

 Inner core: The inner core at the very center of the earth is probably solid and starts at approximately 5,150 kilometers (about 3,200 miles) from the earth’s surface.

 Outer core: Surrounding the inner core is a liquid layer of heavy metals called the outer core. The study of seismic waves and shadow zones allows scientists to determine that the outer core begins at approximately 2,890 kilometers (1,795 miles) into the earth.

There is no way to measure the temperature of the earth’s core. Scientists called geophysicists use laboratory studies of iron under conditions of extreme pressure to estimate how hot it may be at such depths. Their estimates range from 5,000 degrees F to 15,000 degrees F. More accurate measurements cannot be made because the conditions of temperature and pressure at the earth’s core are much too intense to be re-created in a laboratory setting.