The Hydrological Cycle: Evaporation and Condensation

The Hydrological Cycle

• Is the continuous movement of water as a liquid, gas, and solid.
• Water transitions between gas (water vapour) and liquid (rainwater, freshwater, seawater).
• Liquids can freeze into solids like snow and ice.
• This cycle purifies water and replenishes freshwater sources.
• Only 3% of Earth's water is fresh.
• Most freshwater is stored in ice caps (69%) and groundwater (30%).
• Solar energy drives the water cycle through evaporation.

Evaporation

• The process where water changes from liquid to gas, requiring energy input.
• Increased insolation raises the rate of evaporation in water bodies.
• Oceans contribute to most evaporation, covering 70% of Earth's surface.
• Evaporation of ocean water leaves behind salt, minerals, and metals, resulting in freshwater entering the atmosphere.

Condensation

• The change of water from gas to liquid.
• As water vapour rises and cools, it turns into tiny liquid water droplets.
• Latent heat of evaporation is released during condensation.
• Water molecules combine with particles like dust, smoke, and salt to form larger droplets, leading to cloud formation.

Precipitation

• Occurs as rain, snow, sleet, or hail falling from the sky.
• Gravity pulls water back to Earth when clouds become too heavy.
• Water infiltrates the ground, collecting in aquifers (permeable rock, sand, or gravel layers), forming groundwater.
• Groundwater seeps into water bodies.
• Runoff happens when water flows across the land without soaking into the ground, collecting as surface water.
• Snowmelt contributes to runoff, becoming either groundwater or surface water.
• Plant roots absorb groundwater for photosynthesis.
• Transpiration, evaporation from plant leaves, contributes 10% of atmospheric water vapour.
• Evapotranspiration is combined evaporation and transpiration.

Carbon Cycle

• The atmosphere continuously exchanges CO2.
• Natural processes like precipitation, photosynthesis by phytoplankton, erosion, and sedimentation remove CO2 from the atmosphere.
• Cold, sinking water transfers carbon to the ocean's bottom layers.
• Over time, carbon combines with sediment to form limestone, storing carbon for millions of years.
• Warm oceans and currents release carbon back into the atmosphere through evaporation.
• Green plants remove carbon from the atmosphere through photosynthesis, converting it into glucose.
• Oxidation of carbon fuels life, producing carbon waste through respiration, returning it to the atmosphere.
• Burning plants or animal decay releases stored carbon.

Types of Carbon Cycles

• Fast carbon cycle operates within a single lifespan.
• Slow carbon cycle operates over 100 to 200 million years.
• Changes shift carbon between system parts, affecting Earth's temperature.
• The carbon cycle balances carbon levels, acting as a thermostat to stabilize Earth's temperature.

Influences on Earth’s Climate

• Regulates global temperature via CO2 in the atmosphere.
• CO2 helps the atmosphere retain heat, acting as a greenhouse gas.

Disruptions

• Burning fossil fuels releases stored carbon.
• Reduction in carbon sinks occurs through warming oceans, deforestation, and wetland destruction.
• Releasing more stored carbon into the atmosphere.
• Rising CO2 levels contribute to the greenhouse effect, increasing the atmosphere's ability to trap heat.

Statistics

• Atmospheric carbon has risen by 48% since the industrial revolution.
• Global surface temperatures have increased by 1.1 degrees Celsius.