Atmosphere & Altitude (HL) (DP IB Environmental Systems & Societies (ESS))

Atmosphere & Altitude

Atmosphere and gravity

• The atmosphere is made up of layers of gases surrounding the Earth

  • Gravity keeps these layers in place

• Gravity pulls atmospheric molecules towards the Earth's surface

  • This makes the air denser at lower altitudes

• As altitude increases, the strength of gravitational pull decreases because:

  • Gravitational force is inversely proportional to distance from the Earth

  • This inverse relationship means that atmospheric pressure and density decline with altitude

  • This causes the atmosphere to become thinner

Atmospheric thinning with altitude

• Atmospheric thinning refers to the gradual decrease in air density as altitude increases

  • This means fewer molecules are present in a given volume of air at higher altitudes

  • At sea level, the atmosphere is dense, containing a higher concentration of oxygen and other gases

  • As altitude increases, oxygen levels decrease, which can affect breathing and cause altitude sickness

    • For example, high-altitude locations, such as Mount Everest, have significantly thinner air, requiring climbers to use oxygen tanks

Standard lapse rate

• The standard lapse rate describes how temperature decreases with an increase in altitude

  • On average, temperature drops by about 1 degree Celsius for every 100 metres of altitude gained

  • This change in temperature affects weather patterns as well as plant and animal life

    • For example, temperatures at mountain summits are often much colder than temperatures at the base, even though they are geographically close to each other

    • Lower altitudes may have forests, while higher altitudes may be covered in snow or only support low-growing plants