http://www.philosophyforum.net/HistTimeline_files/HistTimeline.htm
For grade 6
For grade 6
Thursday, September 11, 2014
Thursday, April 10, 2014
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The water cycle is a way that water moves all around the Earth. It never stops and doesn't really have a beginning or an end. It's like a big circle. We'll describe it by starting with water that's on land. For example, water in the ocean or a lake. Some water on the surface of the ocean will evaporate due to heat from the sun. When it evaporates it turns into vapor water and goes up into the atmosphere. This vapor water gets together with a lot of other vapor water and turns into clouds. Clouds move about the earth with the weather and once they are so full of water they drop the water to Earth in some form of precipitation. It could be rain, snow, sleet, or hail. When the water hits the earth it may fall right back into the ocean or feed a flower or be snow on the top of a mountain. Eventually this water will evaporate and start the whole cycle again.
How water goes from land to vapor in the atmosphere
There are three main ways that water on land turns into vapor:
Evaporation - This is the main process by which water goes from the ground to vapor in the atmosphere. Around 90 percent of the water vapor in the atmosphere got there through evaporation. Evaporation takes place only on the water's surface. It takes energy in the form of heat. Hot water will evaporate more easily than cold water. The sun provides a lot of the energy for evaporation in the water cycle, primarily causing evaporation from the surface of the ocean.
Sublimation - This is when water moves directly to vapor from ice or snow without ever melting into water. Good conditions for sublimation to occur is when ice or snow is in very cold conditions, but it is windy and the sun is shining.
Transpiration - Transpiration is when plants release water on to their leaves that then evaporates into vapor. Plants will release a lot of water as they grow. Around 10 percent of the water vapor in the atmosphere is estimated to come from transpiration.
Water in the atmosphere
We see water in the atmosphere in the form of clouds. There is a small amount of water even in clear skies, but clouds are where water has started to condense. Condensation is the process of water vapor becoming liquid water. Condensation is a major step in the water cycle. The atmosphere helps to move water around the world. It takes water that evaporated from the ocean and moves it over land where clouds and storms form to water plants with rain.
Precipitation
Precipitation is when water falls from the atmosphere back to land. Once enough water gathers in a cloud droplets of water will form and fall to the earth. Depending on the temperature and weather this could be rain, snow, sleet, or even hail.
Water storage
A lot of the Earth's water does not take part in the water cycle very often., Much of it is stored. The Earth stores water in a number of places. The ocean is the largest storage of water. Around 96 percent of the Earth's water is stored in the ocean. We can't drink the salty ocean water, so fortunately for us, freshwater is also stored in lakes, glaciers, snow caps, rivers, and below the ground in ground water storage.
There are three main ways that water on land turns into vapor:
Evaporation - This is the main process by which water goes from the ground to vapor in the atmosphere. Around 90 percent of the water vapor in the atmosphere got there through evaporation. Evaporation takes place only on the water's surface. It takes energy in the form of heat. Hot water will evaporate more easily than cold water. The sun provides a lot of the energy for evaporation in the water cycle, primarily causing evaporation from the surface of the ocean.
Sublimation - This is when water moves directly to vapor from ice or snow without ever melting into water. Good conditions for sublimation to occur is when ice or snow is in very cold conditions, but it is windy and the sun is shining.
Transpiration - Transpiration is when plants release water on to their leaves that then evaporates into vapor. Plants will release a lot of water as they grow. Around 10 percent of the water vapor in the atmosphere is estimated to come from transpiration.
Water in the atmosphere
We see water in the atmosphere in the form of clouds. There is a small amount of water even in clear skies, but clouds are where water has started to condense. Condensation is the process of water vapor becoming liquid water. Condensation is a major step in the water cycle. The atmosphere helps to move water around the world. It takes water that evaporated from the ocean and moves it over land where clouds and storms form to water plants with rain.
Precipitation
Precipitation is when water falls from the atmosphere back to land. Once enough water gathers in a cloud droplets of water will form and fall to the earth. Depending on the temperature and weather this could be rain, snow, sleet, or even hail.
Water storage
A lot of the Earth's water does not take part in the water cycle very often., Much of it is stored. The Earth stores water in a number of places. The ocean is the largest storage of water. Around 96 percent of the Earth's water is stored in the ocean. We can't drink the salty ocean water, so fortunately for us, freshwater is also stored in lakes, glaciers, snow caps, rivers, and below the ground in ground water storage.
Composition of the Earth
It may seem like the Earth is made up of one big solid rock, but it's really made up of a number of parts. Some of them constantly moving! You can think of the Earth as being made up of a number of layers, sort of like an onion. These layers get more and more dense the closer to the center of the earth you get. See the picture below to see the four main layers of the earth: the crust, mantle, outer core, and inner core.
Crust
The crust is the thin outer later of the Earth where we live. Well, it looks thin on the picture and it is thin relative to the other layers, but don't worry, we're not going to fall through by accident anytime soon. The crust varies from around 5km thick (in the ocean floor) to around 70km thick (on land where we live called the continental crust). The continental crust is made up of rocks that consist primarily of silica and alumina called the "sial".
Mantle
The next layer of the Earth is called the mantle. The mantle is much thicker than the crust at almost 3000km deep. It's made up of slightly different silicate rocks with more magnesium and iron.
Tectonic plates
The tectonic plates are a combination of the crust and the outer mantle, also called the lithosphere. These plates move very slowly, around a couple of inches a year. Where the plates touch each other is called a fault. When the plates move and the boundaries bump up against each other it can cause an earthquake.
Outer Core
The Earth's outer core is made up of iron and nickel and is very hot (4400 to 5000+ degrees C). This is so hot that the iron and nickel metals are liquid! The outer core is very important to earth as it creates something called a magnetic field. The magnetic field the outer core creates goes way out in to space and makes a protective barrier around the earth that shields us from the sun's damaging solar wind.
Inner Core
The Earth's inner core is made up of iron and nickel, just like the outer core, however, the inner core is different. The inner core is so deep within the earth that it's under immense pressure. So much pressure that, even though it is so hot, it is solid. The inner core is the hottest part of the Earth, and, at over 5000 degrees C, is about as hot as the surface of the sun.
The crust is the thin outer later of the Earth where we live. Well, it looks thin on the picture and it is thin relative to the other layers, but don't worry, we're not going to fall through by accident anytime soon. The crust varies from around 5km thick (in the ocean floor) to around 70km thick (on land where we live called the continental crust). The continental crust is made up of rocks that consist primarily of silica and alumina called the "sial".
Mantle
The next layer of the Earth is called the mantle. The mantle is much thicker than the crust at almost 3000km deep. It's made up of slightly different silicate rocks with more magnesium and iron.
Tectonic plates
The tectonic plates are a combination of the crust and the outer mantle, also called the lithosphere. These plates move very slowly, around a couple of inches a year. Where the plates touch each other is called a fault. When the plates move and the boundaries bump up against each other it can cause an earthquake.
Outer Core
The Earth's outer core is made up of iron and nickel and is very hot (4400 to 5000+ degrees C). This is so hot that the iron and nickel metals are liquid! The outer core is very important to earth as it creates something called a magnetic field. The magnetic field the outer core creates goes way out in to space and makes a protective barrier around the earth that shields us from the sun's damaging solar wind.
Inner Core
The Earth's inner core is made up of iron and nickel, just like the outer core, however, the inner core is different. The inner core is so deep within the earth that it's under immense pressure. So much pressure that, even though it is so hot, it is solid. The inner core is the hottest part of the Earth, and, at over 5000 degrees C, is about as hot as the surface of the sun.
The Earth is unlike every other planet in the Solar System in a number of different ways.
- It is the only planet that has an atmosphere containing 21 percent oxygen.
- It is the only planet that has liquid water on its surface.
- It is the only planet in the solar system that has life.
- The Earth is the only inner planet (Mercury, Venus, Earth and Mars) to have one large satellite, the Moon. Mars has two very tiny moons. Mercury and Venus have none.
- The Earth is fragile. Its surface is split into plates (tectonic plates) which float on a rocky mantle – the layer between the surface of the earth, its crust, and its hot liquid core. The inside of the Earth is active andearthquakes, volcanoes and mountain building takes place along the boundaries of the tectonic plates.
- When viewed from outer space much of the Earth’s surface cannot be seen because of clouds of water vapour. The water vapour makes the Earth, when seen from outside, into a brilliant shining orb, as you can see in Figure 1.
- The Earth is the third planet from the Sun and comes between the planet Venus and the planet Mars.
- The Earth takes 365¼ days to complete its orbit round the Sun. The Earth’s year is therefore 365 days long but the ¼ days are added up and every fourth year has one extra day, on the 29th of February. This fourth year is called a Leap Year (366 days) and is always a year which can be divided exactly by 4 – 2000, 2004, 2008, 2012, 2016.
- The planets closer to the Sun, Mercury and Venus, have shorter years than the Earth. The planets further away from the Sun have longer years; Pluto takes 249 of our years to make one orbit of the Sun.
- As the Earth orbits round the Sun it turns on its axis, rotating right round in 24 hours. The side of the Earth that faces the Sun has daytime and the side of the Earth that is turned away from the Sun has night-time. When it is daytime in Britain, it is night-time on the opposite side of the Earth in New Zealand.
- As the Earth orbits round the Sun it tilts very slightly and so gives us the seasons. When the Earth has tilted so that the northern half of the Earth is a little away from the Sun, the northern hemisphere (meaning half of the Earth’s sphere) has winter.
- Figure 2. The planets of the Solar System.
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