4.4 Earth's Atmosphere

What is the most abundant gas in Earth's atmosphere?

Nitrogen, making up approximately 78% of the atmosphere.

What role does oxygen play in Earth's atmosphere?

Oxygen, accounting for about 21%, is produced by photosynthesis and is essential for human and animal respiration.

What is the percentage and characteristic of argon in the atmosphere?

Argon makes up about 0.93% of the atmosphere and is an inert, noble gas.

What is the significance of water vapor in the atmosphere?

Water vapor constitutes about 0.4% of the atmosphere, varies by region, acts as a temporary greenhouse gas, and cycles quickly through the atmosphere.

What is the concentration of carbon dioxide in the atmosphere and its importance?

Carbon dioxide is present at about 0.04% and is the most important greenhouse gas, contributing to global warming.

What is the exosphere?

The exosphere is the outermost layer of Earth's atmosphere where it merges with space.

What are the characteristics of the thermosphere?

The thermosphere is the hottest layer, absorbs harmful X-rays and UV radiation, and causes charged gas molecules to glow, producing the northern lights.

What is the mesosphere and its temperature characteristics?

The mesosphere is the middle layer of the atmosphere, located at 60-80 km, and is the coldest layer, with temperatures decreasing due to lower density.

What is the significance of the stratosphere?

The stratosphere, located between 16-60 km, contains the thickest ozone layer which absorbs UV-B and UV-C rays, protecting living organisms from DNA mutations.

What occurs in the troposphere?

The troposphere, extending from 0-16 km, is the densest layer where weather occurs and contains most of the atmosphere's gas molecules and water vapor.

What is the temperature gradient in the thermosphere?

In the thermosphere, temperature increases due to the absorption of highly energetic solar radiation, making it the hottest place on Earth at about 3,100°F.

What happens to temperature in the mesosphere?

In the mesosphere, temperature decreases as density decreases, making it the coldest place on Earth at approximately -150°F.

How does temperature change in the stratosphere?

In the stratosphere, temperature increases because the top layer is warmed by UV rays.

What is the temperature behavior in the troposphere?

In the troposphere, temperature decreases as altitude increases, moving away from the warmth of Earth's surface.

What happens to warm air in the atmosphere?

Warm air rises because it is less dense and can hold more moisture than cold air.

What is adiabatic cooling?

Adiabatic cooling occurs when rising air expands in volume due to less pressure, causing it to cool.

What is the result of cool air in terms of water vapor?

Cool air cannot hold as much water vapor, leading to condensation and precipitation.

What happens to sinking air in the atmosphere?

Sinking air experiences more pressure, decreases in volume, and warms up due to adiabatic warming.