Weather front is the boundary between two masses of air with different densities, temperature and humidity.There are four types of weather fronts: cold front (cold air mass, thunderstorms and rain) , warm front (warm air mass,smaller density than the cold front), occluded front (low pressure ares), it is formed when cold front overtakes a warm front) and stationary front , the boundary between two air masses that are not strong to be either both cold or both warm (clouds, precipitation).
Answer:
plants did it
Explanation:
The development of organisms capable of photosynthesis caused Earth's atmospheric oxygen to increase. These organisms use carbon dioxide and water to form sugar and oxygen.