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What are the Steps of the Water Cycle?
Some scientists now believe that Earth's water derived from a thick hydrogen-rich layer which reacted with oxides in the Earth's mantle creating water which filled basins forming our lakes and seas. Earlier scientists believed that in the very hot and dry period of Earth's history shortly after its formation (about 3.8 billion years ago), millions of asteroids and comets which were water-rich collided with our planet creating the oceans and seas.
Because water is essential to both the origin and continual evolution of life on Earth, where this life-giving nutrient ultimately came from has fascinated scientists for decades and the debate of where our water originated continues today.
Not only is there debate regarding the origin of water on Earth, there is also a new theory regarding the system of water 'recycling' throughout our planet. The original theory of water cycling on earth came from Bernard Palissy in 1580 who theorized an atmospheric water cycle which is a closed system meaning water neither leaves or enters Earth. Recently, a new definition of the cyclical nature of water has been proposed by William Waterway which demonstrates an interaction between three water cycles -the oceanic, atmospheric and cosmic
Watch the Water Cycle as provided by NASA
The Traditional Atmospheric Water Cycle
Bernard Palissy developed the original theory of the cyclical nature of water 430 years ago. His water cycle definition was published in his book, Discours Admirables. His theory describes a closed system where the quantity of water on Earth remains constant but is in constant motion. The same water molecules according to Palissy have been constantly recycled around the Earth since their appearance over 3 billion years ago. The endless circulation of water occurs through the processes of evaporation, condensation, and precipitation
The Atmospheric Water Cycle is powered by the sun. Water is stored on earth in oceans, lakes, streams and groundwater. It is also stored in the atmosphere in the form of water vapour and condensation in the form of clouds.
- During evaporation, sun's energy heats up water molecules, in all water bodies, enough that they break free of the attractive forces keeping them together as a liquid.
- The molecules become a gas or vapour rising up into the atmosphere.
- Snow may also sublimate directly into vapour from the solid state sending water vapour into the atmosphere.
- Plants contain enormous amounts of water and their leaves have pores through which water escapes in a process known as evapotranspiration.
- 5 to 10 times as much water is transpired by plants as they can hold at any one time.
- Water vapour rises into the air and as it does so it cools, turning back into liquid water or solid water (ice, hail, or snow) which collects on tiny particles of dust.
- This process is known as condensation and a large collection of these water particles forms clouds of liquid or solid water.
- Precipitation in the form of rain, snow, sleet or hail comes from clouds.
- When enough condensation has collected and the cloud is 'heavy' enough precipitate falls to earth.
- Runoff results from rain or snowmelt that flows downhill into streams, lakes and oceans.
- Runoff is visible as the water stored in the river and lake basins drains out.
- Percolation of some precipitation occurs.
- This water seeps into cracks, pores and joints of soil and rocks until it reaches the water table where it becomes groundwater.
- Groundwater is underground water held in cracks and pores of subterranean rock, sand and gravel.
- Some groundwater supports streams and some is tapped for wells in rural areas.
- Some groundwater is extremely old and may have existed as such for thousands of years.
Although the hydrologic cycle balances the amount of water entering the atmosphere, with the amount of precipitation returning to earth, there is an imbalance in temperate climates. For example, during the Canadian winter, most precipitate is frozen and locked up in solid form on the ground as snow or ice. During the spring thaw, huge amounts of liquid water are quickly released into water bodies creating huge spring runoff and flooding.
Climate plays an important role in the hydrologic cycle as average temperatures are important in the amount of rainfall an area will receive. However, water itself, has an important impact on the climate of a given area.
- Large bodies of water trap enormous quantities of heat.
- Areas near large bodies of water will have a moderation of their climate due to their proximity to this large water body.
- In the winter, these areas experience milder temperatures as the heat stored within the water body is slowly released to the surrounding atmosphere.
- The opposite is true in the summer months when a cooling affect is experienced due to the massive amounts of heat being absorbed by the water.
Water also acts as an energy transfer and storage medium for the climate system.
- Evaporation of water requires an enormous amount of energy from the sun which is trapped in water vapour.
- As the water vapour condenses to precipitation, this energy is released again as heat. This is one of the processes that has made life possible on earth.
- Fresh water stored on earth in the forms of glaciers, snow and ice contains trapped latent or potential energy; thus, also moderating the earth's climate.
Understanding of the atmospheric water cycle is very important in understanding other chemical processes and cycles of our planet as all tend to have overlapping components.
New Theory: The Waterway Cycle
William Waterway completed years of research and observations of the cyclical nature of water and presented a new definition for Earth's water cycle at the International Symposium of Aqua Science and Water Resources. This new research, although still supporting the Atmospheric Cycle of Palissy to some extent, suggests a more interactive nature of Earth's water cycle which has been named the waterway cycle.
- Earth's water cycle is now seen as more of an open system connecting our water resources from the molten inner core of Earth to water present in the surrounding universe.
- The waterway cycle is composed of three interacting cycles:
- The Oceanic water cycle;
- The Atmospheric water cycle;
- The Cosmic water cycle.
1. The Oceanic Water Cycle:
- Depends upon research suggesting that oceanic water circulates towards the core of our planet due to colliding tectonic plates.
- As one plate collides with another and sinks below that plate, sea floor saturated with water also sinks below abutting plates.
- The sea water saturating the sinking plates becomes superheated by the earth's core, melting the mantle overtop of them creating magma and gas vents.
- These gas vents, called mid-ocean ridges, circulate ancient seawater through deep ocean fractures.
- These vents create new sea floor.
- Magma venting onto land creates new landmass.
- Through this process, it is suggested that all of the oceans waters are recycled every 6 to 8 million years.
- This particular water cycle is important in maintaining the mineral and biochemical revitilization of our oceans and continents.
- It supports continued biodiversity of our planet.
2. The Atmospheric Water Cycle
- This cycle is based on Palissy's work from 1580 and is supported still today as part of the larger picture of our Earth's recycling of water.
- It is sun driven.
- It involves the processes of evaporation, condensation, precipitation, and collection in basins due to runoff.
- This cycle is essential in maintaining atmospheric and surface water supplies and supporting the Earth's biodiversity.
3. The Cosmic Water Cycle
- This cycle is based on the most recent research.
- Extraterrestrial water was first documented as having entered the Earth's atmosphere in 1999.
- Meterorites and asteroids and other sources bring water with them when they enter our atmosphere.
- When these cosmic sources of water enter our lower atmosphere, not only water but other bio-molecules such as amino acids are deposited.
- Not only does Earth gain water from space, it also loses a small quantity due to solar wind and other influences.
- It is estimated that the Earth loses a ton of atmosphere to space every hour along with the water vapour associated with that atmosphere.
- Although the amount of water involved in the Cosmic Water cycle is very small, it is now considered to be an essential contribution to Earth's biodiversity.
Without water, life on earth as we know it would not exist. The water present on our Earth owes its presence to a more complex series of cycles than previously understood. From the Earth's core, to the surrounding universe, water sources interact providing us with the continual cycling of this life-giving compound which has resulted in the tremendous diversity of life found on our planet.