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8th Grade Earth Science
Chapter17 Key Terms
Section 1
1. air mass: a huge body of air that has similar temperature, humidity, and air pressure
throughout
2. anticyclone: a high-pressure system of dry air
3. continental: a dry air mass that forms over land
4. cyclone: a swirling center of low air pressure
5. front: the boundary where unlike air masses meet but do not mix
6. maritime: a humid air mass that forms over oceans
7. occluded: cut off, as in a front where warm air mass is caught between two cooler air
masses
8. polar: a cold air mass that forms north of 50o north latitude or south of 50o south
latitude and has high air pressure
9. tropical a warm air mass that forms in the tropics and has low air pressure
Section 2
1. evacuate: to move away from an area temporarily to avoid hurricane conditions
2. hurricane: a tropical storm that has winds of about 119 kilometers per hour or higher
3. lightning: a sudden spark, or energy discharge, caused when electrical charges jump
between parts of a cloud, between nearby clouds, or between a cloud and the ground
4. storm: a violent disturbance in the atmosphere
5. storm surge: a “dome” of water that sweeps across the coast where a hurricane
lands.
6. thunderstorm: a small storm accompanied by heavy precipitation and frequent
thunder and lightning
7. tornado: a rapidly whirling, funnel-shaped cloud that reaches down from a storm
cloud to touch Earth’s surface.
Section 3
1. isobar: a line on a weather map that joins places that have the same air pressure
2. isotherm: a line on a weather map that joins places that have the same temperature
3. meteorologist: a scientist who studies the causes of weather and tries to predict it