| A | B |
|---|
| geology | the study of planet Earth, its structure, compostion, and how it has changed over time |
| nebular hypothesis | most accepted scientific model of formation of our solar system |
| planetesimals | all planets started as these large bodies |
| inner core | solid innermost layer of Earth, composed of iron & nickel under extreme high pressure & temperature |
| outer core | layer of Earth's interior located between the inner core and mantle, composed of iron & nickel in a liquid state |
| mantle | thickest of Earth's layers, between crust and outer core, composed of iron, silicon, magnesium |
| crust | very thin layer of Earth above the mantle, composed of a rigid layer of rocks-65 km at deepest |
| lithosphere | the outer shell of the Earth consisting of the crust and uppermost portion of the mantle |
| asthenosphere | partially melted layer of the mantle that underlies the lithosphere |
| magnetic field | motion of charged particles creates a magnetic force |
| rotation | turning of a body, such as Earth, on its axis |
| standard time zones | areas roughly defined by twenty-four 15 degree sections of longitude, on a time meridian establishing the hour of the day |
| time meridian | a line of longitude exactly divisible by 15 degrees on which each standard time zone is centered |
| prime meridian | imaginary line dividing Earth's surface into Eastern and Western Hemispheres, 0 degrees at Greenwich, England |
| International Date Line | imaginary line placed at roughly 180 degrees longitude-new calendar begins, moving east to west |
| revolution | movement of one body around another, such as the Earth's orbit around the sun |
| parallax | apparent shift in one object's position relative to another caused by a change in the location of the observer |
| summer solstice | first day of summer in Norther Hemisphere, on June 21 when sun appears to reach most northern point in sky |
| winter solstice | first day of winter in Northern Hemisphere, on December 21 noon sun appears most southern point in sky |
| vernal equinox | start of spring in the Northern Hemisphere, on March 21 sun is directly over the equator, day & night are equal |
| autumnal equinox | start of fall in the Northern Hemisphere(Sept. 22) when the noon sun is directly over the equator-day & night equal |
| zenith | the point directly above the observer referred to by astronomers |
