Chapter 4, Earths Structure and Motion
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25 terms
Terms | Definitions |
|---|---|
 oblate spheroid | The shape of the Earth, which is a sphere that bulges in the center. |
| inner core | The Earth's center, which is composed of solid iron and nickel. |
| outer core | The layer of liquid iron and nickel that is directly above the inner core. |
| mantle | The thickest of Earth's layers, which is directly above the outer core. It is composed mostly of compounds rich in iron, silicon, and magnesium. |
| lithosphere | The crust and the uppermost portion of the mantle. |
| asthenosphere | A thin, slush like layer of the mantle that the more rigid material of the lithosphere floats upon. |
| magnetic field | The lines of magnetic force that surround the Earth and protect it from the sun's deadly solar wind. |
| rotation | The spinning of the Earth on its axis. |
| Foucault pendulum | An iron sphere on a very long wire, that gives evidence that the Earth rotates on its axis. |
| Coriolis effect | The apparent deflection of the winds caused by the spinning of the Earth on its axis. |
| time meridian | Each standard time zone which is roughly centered on a line of longitude exactly divisible by 15º. |
| prime meridian | An arbitrary longitude line which is the starting point for the standard time zones. |
| International Date Line | An imaginary line that represents the longitude at which the date changes. |
| revolution | The movement of the Earth in its orbit around the sun. |
| parallax | The apparent shift in positions of nearby stars compared to distant stars. This is evidence of the Earth's revolution around the sun. |
| summer solstice | The day in which we have maximum daylight. In the Northern Hemisphere this happens around June 21. |
| winter solstice | The day in which we have the least amount of daylight. In the Northern Hemisphere this happens around December 21. |
| vernal equinox | The day in March when there are 12 hours of daylight and 12 hours of night. |
| autumnal equinox | The day in September when there are 12 hours of daylight and 12 hours of night. |
| perihelion | The point in the Earth's orbit in which the Earth is closest to the Sun. |
| aphelion | The point in the Earth's orbit in which the Earth is farthest from the Sun. |
| Arctic Circle | The latitude line that is 23.5º below the North Pole. Areas above this line have 24 hours of darkness on Dec. 21st |
| Antarctic Circle | The latitude line that is 23.5º above the South Pole. Areas below this line have 24 hours of darkness on June 21st |
| Tropic of Cancer | The latitude line that is 23.5º above the equator. Areas on this line have the sun directly overhead on June 21st. |
| Tropic of Capricorn | The latitude line that is 23.5º below the equator. Areas on this line have the sun directly overhead on Dec 21st. |
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