| A | B |
|---|
| geography | the study of earth in all its variety |
| landform | individual features of the land, such as mountains and valleys |
| environment | natural surroundings |
| Global Positioning System | a device that receives signals from satellites |
| Geographic Information System | computer software that helps geographers gather many types of information about a region |
| artifact | tools, pottery, paintings, weapons, and other items left behind by past societies |
| fossil | preserved remains of early humans, animals, or plants |
| solar system | Earth, seven other planets, and thousands of smaller bodies that all revolve around the sun |
| orbit | path that a body in the solar system travels around the sun |
| atmosphere | layer of air surrounding Earth |
| axis | imaginary line that runs through Earth's center between the north and south poles |
| revolution | one complete orbit around the sun |
| leap year | year that has an extra day; occurs every fourth year |
| summer solstice | day with the most hours of sunlight and the fewest hours of darkness |
| equinox | day when day and night are of equal length in both hemispheres |
| core | center of Earth formed of hot iron mixed with other metals |
| mantle | rock layer about 1,800 miles thick between Earth's core and crust |
| magma | hot, melted rock that sometimes flows to Earth's surface in a volcanic eruption |
| crust | uppermost layer of Earth |
| continent | massive land area |
| plate tectonics | theory that Earth's crust is not an unbroken shell but consists of plates, or huge slabs of rock, that move |
| earthquake | violent and sudden movement of Earth's crust |
| tsunami | huge sea wave caused by an earthquake on the ocean floor |
| fault | crack in Earth's crust |
| weathering | natural process that breaks surface rocks into boulders, gravel, sand, and soil |
| erosion | process of wearing away or moving weathered material on Earth's surface |
| glacier | giant slow-moving sheets of ice |
| elevation | height above sea level |
| plain | low-lying stretch of flat or gently rolling land |
| plateau | flat land with higher elevation than a plain |
| isthmus | narrow piece of land that connects two larger pieces of land |
| peninsula | piece of land with water on three sides |
| island | body of land smaller than a continent and surrounded by water |
| continental shelf | plateau off each coast of a continent that lies under the ocean and stretches for several miles |
| trench | valley in the ocean floor |
| strait | narrow body of water between two pieces of land |
| channel | body of water wider than a strait between two pieces of land |
| delta | area formed from a soil deposit located at the mouth of a river |
