Wednesday, April 9- Earth - Interaction Between the Earth's Systems
Objective: Earth’s systems interact, resulting in a variety of effects, some of which are disastrous.
We all talk about the weather and have an interest in it. It is defined as the condition of the atmosphere at a particular place and time.
Water is constantly moving between Earth’s surface and the atmosphere in the water cycle. Humidity is the amount of water vapor present in the air. The ability of air to hold water vapor is related to temperature. Warmer air can hold more water vapor. Clouds form when warm, moist air rises into the atmosphere and cools. As the air cools to a temperature where the air is completely saturated, water vapor condenses around small particles like dust or sea salt and forms water droplets or ice particles. A cloud is a collection of millions of water droplets. Precipitation falls from the clouds.
Changes in the weather are caused my movements of air masses – a large body of air that takes on the temperature and moisture characteristics over which it forms. Weather systems form when the air remains over the same region for a period of days and weeks. For example, an air mass that develops over the Gulf of Mexico will be warm and wet.
At Earth’s middle latitudes, weather systems with different characteristics sometimes meet. The boundary that forms between them is called a front – a narrow region separating two air masses. Fronts are usually associated with weather in the middle latitudes where there can be warm and cool air. A front usually signifies a change of weather. Fronts don’t exist in the Tropics.
A cold front forms when a cold air mass meets and displaces a warm air mass. Because the cold front is denser, it moves under the warm air and causes it to rise. The warm air rises, cools and the water vapor condenses. Cold air fronts can produce clouds, thunderstorms, rain or sow.
A warm front forms when a warm air mass meets and overrides a cold air mass and replaces it. The air ahead of a warm front usually produces a boundary that is less steep. Warm fronts usually bring cloudiness and drizzly rain. After it passes, the weather is usually warm and clear.
When weather systems interact, you can get natural disasters, such as thunderstorms, tornadoes and hurricanes.
Thunderstorms develop when the air is warm and moist. As the warm air moves up, it cools, condenses and forms clouds. That water droplets fall back to Earth and cools the surrounding air, which becomes denser. The dense air sinks quickly, creating a downdraft that causes strong winds.
Tornadoes are a rotating column of air that is in touch with the ground and a cloud. When the conditions are right, the air near the Earth’s surface may move horizontally. It this air is close enough to a thunderstorm’s upward-moving winds, the air gets pulled from a horizontal position to a vertical position.
Hurricanes are large, rotating low-pressure storms that form over warm, tropical waters. Hurricanes need a large supply of warm ocean water and a disturbance to lift the warm air up and keep it rising. Usually a hurricane begins as a group of thunderstorms. As the hurricane intensifies, more warm air moves to replace air that has risen. Energy is released through the cooling and condensing of the air producing rain and powerful winds.
The Earth is constantly changing. Weathering is the breaking down of rock into smaller pieces through a natural process. Weather can be mechanical (ice, water, animals, etc. cause rocks to break); chemical (changes in the rock because it is exposed to air, water – rust on iron is an example); and through plants and animals (plants growing through cracks in a rock).
Erosion is the transport of weathered materials from one place to another. Deposition is when the eroded material is laid on the ground or sinks to the bottom of a body of water. The three main agents of erosion are gravity, wind and water. This process of erosion can cause much of the land forms we see on the earth. For example a hillside covered with loose rocks (gravity), a sand dune (wind), the Grand Canyon (water from the Colorado River).
Erosion can cause a lot of problems for farmers. In the 1930s, farmers in the Central Plains overused their land and didn’t give it time to recover. The crops grown in the soil were weak and when drought came, the crops died. With no plant roots to hold the soil down, high winds blew much of the topsoil away, creating the Dust Bowl. The government now has programs to teach soil conservation and financially assist farmers.