| A | B |
|---|
| Asthenosphere | The Weak Layer of soft but solid rock comprising the lower part of the upper mantle (below the lithosphere) and over which the plates slide. |
| Climate System | A goesystem that includes all parts of the Earth System and all the interactions among these components needed to describe how climate behaves in space and time. |
| Core | The central part of the Earth below a depth of 2900 km comprising a liquid outer core and a solid inner core. The core is composed of iron and nickel, with minor amounts of some lighter element, such as oxygenor sulfur. |
| Eath System | All the parts of our planet and all their interactions, taken together. |
| Fossil | Trace of an organism of past geologic ages that has been preserved in the crust. |
| Geodynamo | The goesystem that sutains Earth's magnetic field, driven by covection in the ourter core. |
| Geosystem | A specialized subsytem of the Earth system that encompasses specific types of terrestrial behavior. |
| Inner Core | The central part of the Earth from a depth of 5150 to 6370 km, composed of iron and nickel. |
| Lithosphere | The strong, rigid outer shell of the Earth that encases the asthenosphere and contains the crust and the uppermost part of the mantle down to an average depth of about 100 km and forms the rigid plates. |
| Magnetic Field | The region of influence of a magnetized body ro an electric current. |
| Mantle | The region that forms tha main bulk of the solid Earth, between the crust and core, ranging from depths of about 40 km to 2900 km. |
| Outer Core | A liquid zone-composed of iron, nickel, and minor amountsof some lighter element, such as oxygen or sulfur-below the mantle, from a depth of 2890 to 5190 km, that surrounds a solid iron-nickel inner core. |
| Plate Tectonic System | A geosystem that includes all parts of the Earth system and all the interactions among these components needed to describe how plate tectonics works in space and time. |
| Princilple of Uniformitarianism | The Principle that the geologic processes we see in action today have worked in much the same way throughout geologic time; that is, "the present is the key to the past" |
| Scientific Method | A general research plan, based on methodical observations and experiments, by which scientific propose and test hypothesis that explain some aspect of how the universe works. |
| Topgraphy | The general configuration of varying heights that gives shape to Earth's surface. |
| Siesmic Wave | A ground vibration produced by earthquakes or explosions. |
