Wednesday, 2 April 2014

The atmosphere

The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space.

1) The troposphere
The troposphere is the first layer above the surface and contains half of the Earth's atmosphere. Weather occurs in this layer. Weather in this layer affects our daily life.

Between 7 to 14 kilometres.
The higher, the colder.
2) The stratosphere
Many jet aircrafts fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.

Starts at 14 to 50 kilometres.
The higher, the hotter.
3) The mesosphere.
Meteors or rock fragments burn up in the mesosphere.

Between 50 to 85 kilometres.
The higher, the colder.
4) The thermosphere.
The thermosphere is a layer with auroras. It is also where the space shuttle orbits.

Between 85 to 640 kilometres or higher.
The higher, the hotter.
5) The exosphere.
The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.

640 kilometres or higher.

The water cycle

Water is essential for life as we know it. The water cycle is the cycle that water goes through on Earth. It makes the rain, clouds, and most of our weather. 

The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above and below the surface of the Earth. Water can change states among liquid, vapour, and solid at several places in the water cycle.

The sun, which drives the water cycle, heats water in oceans and seas. Water evaporates as water vapour into the air. Rising air currents take the vapour up into the atmosphere where cooler temperatures cause it to condense into clouds. Air currents move water vapour around the globe, cloud particles fall out of the sky as precipitation. Some precipitation falls as snow or hail.

Most water falls back into the oceans or onto land as rain, where the water flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, moving water towards the oceans. Not all runoff flows into rivers, much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers, which store freshwater for long periods of time.

Over time, the water returns to the ocean, where the water cycle started.

The water cycle

  1. - First, water on the earth, in lakes, in oceans and in the sea is evaporated by the heat from the Sun.
  2. - Excess water from plants is also absorbed into the atmosphere, this process is called transpiration.
  3. - Then, water collects as water vapor in the sky. This makes clouds.
  4. - Next, the water in the clouds gets cold. This makes it become liquid again. This process is called condensation.
  5. - Then, the water falls from the sky as rain, snow, sleet, or hail which is called precipitation.
  6. -The water then collects into lakes, oceans, or aquifers. From there, it evaporates again and continues the cycle.