Page 29 - Curriculum Visions Dynamic Book

The water cycle
The water cycle is unique to the Earth. Because water can exist as liquid and vapor in the range of Earth temperatures, evaporation and condensation are common events. They are not common elsewhere in the Solar System.
Water is stored in the clouds in the form of water droplets. These droplets also reflect solAr rAdiAtion back to space.
Water turns into
gas by evaporation.
It then rises due
to either heating
(a process called convection) or global winds. Condensation occurs at higher levels to produce clouds.
Precipitation occurs when the water droplets or snowflakes are big enough to fall against the updrafts that produce the cloud.
The unique role of plants on planet Earth is shown in part by the way they influence natural cycles. In this case plants take in water through their roots and transpire it back to the air.
The majority of the water on the Earth is in the form of liquid water in the oceans. Solar radiation provides the energy to turn a small part of it into gas to produce water vapor in the air.
As water flows as rivers, the energy of the moving water can cause erosion and thus alter the shape of the planet’s surface (see page 40). Chemical reactions can also occur, so that rocks are dissolved away as part of the water cycle.
The Earth has unique rocks because of the rock cycle (see pages 40–41). Although rocks on other planets are impermeable lAvAs, many rocks on the Earth are sedimentAry. They make up the majority of the water-bearing rocks on Earth. Water is stored in these rocks and slowly transferred to rivers.
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