Final answer:
A cold front forms when cold, dense air moves under warm, less dense air. This movement causes cooler weather to follow the cold front. Low-pressure systems occur when the earth's surface atmospheric pressure is lower than the surrounding environment, resulting in the rising of moist air and the production of clouds.
Step-by-step explanation:
A cold front forms when cold, dense air moves under warm, less dense air. This movement causes cooler weather to follow the cold front. Cold fronts often bring other weather changes along with them. Low-pressure systems occur when the earth's surface atmospheric pressure is lower than the surrounding environment, resulting in the rising of moist air and the production of clouds. The movement of moisture and air within various weather fronts causes most weather events.