Environments Through Time

OUTCOMESBy the end of this topic you should be able to: Describe the interacting subsystems of Earth that together produce a unique biomeExplain why water is an essential ingredient in the maintenance of the Australian environmentDescribe how water plays an important part in weathering and the subsequent production of soilsOutline water resources, past and present

Water IssuesTopic OverviewThere are 5 parts to this topicSpheres of the EarthThe importance of water as a solvent in Biological SystemsThe hydrologic cycleAustralias Aquatic Past

Spheres of the Earth

Part 1-Lesson 1IntroductionThree quarters of Earth is covered by water. This liquid water which we have so much of is what makes us unique from different planets. Its very rare in our solar system.

IntroductionWater is one of the key reasons why Earth is able to sustain life. Water is often what scientists are looking for on other planets in the search for other forms of life in our solar system.

IntroductionThe rocks that form the skeleton of our planet have been slowly eroded away by the actions of water over time. This has resulted in soils in which we depend upon to grow food.

Introduction Of the abundant water on Earth, very little of it is fresh. The distribution of this fresh water is what determines types of habitats. All Australian environments reflect the quality and amount of water they receive each year.

IntroductionHuman activities have altered the quality and distribution of water in this country and countries around the world. Governments are now struggling to protect this resource which is one of our most important.

In this section we will look at water on our planet and why its so important.

Spheres of the EarthScientists refer to the Earth in different spheres. These spheres are a zone in which a particular feature is found.AtmosphereLithosphereHydrosphereBiosphere

AtmosphereThis is the zone of gases that extend from the surface upwards until outerspace. There is a gradual thinning of gasses and no clear boundary between the atmosphere and space.

AtmosphereAir particles have been detected at heights of 1000km. The space shuttle orbits the Earth at about 300km!

According to NASA, they define space at an altitude of 85km. About 80% of the atmospheres mass is in the bottom 12 kilometres.

LithosphereThis is the zone of rigid rock that extends from the surface down to the mantle where the rock becomes partially molten. The depth of the lithosphere varies from 5-100 kilometres.

Its average is around 70km.

HydrosphereThis is the zone of water which extends from within the lithosphere and possibly mantle to about 12 kilometres into the atmosphere. Water in the hydrosphere can occur as ice, vapour and liquid.

BiosphereThis is the zone of which life can be found. The biosphere can be has high as 12km above ground and deep within the Earth. The depth is uncertain however scientists have estimated this to be between 5-10km.

Natural Events That Impact on These Spheres We are very familiar with the effects of floods, fire and drought in Australia. These events can affect the atmosphere, lithosphere, hydrosphere and biosphere in a number of ways.

Natural Events That Impact on These Spheres Other less common events which impact on these spheres include volcanic eruptions, earthquakes, ice ages and meteorite collisions.

See the table on page 85 Prelim Spotlight Text to examine some natural events and their frequency.

ReviewThree quarters of Earth is covered by water. This liquid water which we have so much of is what makes us unique from different planets. Its very rare in our solar system.Scientists refer to the Earth in different spheres. These spheres are a zone in which a particular feature is found.AtmosphereLithosphereHydrosphereBiosphereNatural events can affect the atmosphere, lithosphere, hydrosphere and biosphere in a number of ways.HomeworkRead pages 82-85 Prelim Spotlight TextStart new electronic vocabulary list for this module

Spheres of the EarthPart 1-Lesson 2ReviewThree quarters of Earth is covered by water. This liquid water which we have so much of is what makes us unique from different planets. Its very rare in our solar system.Scientists refer to the Earth in different spheres. These spheres are a zone in which a particular feature is found.AtmosphereLithosphereHydrosphereBiosphereNatural events can affect the atmosphere, lithosphere, hydrosphere and biosphere in a number of ways.Global Water BudgetThe GWB refers to the total distribution of water in all its forms and reservoirs on Earth. This distribution is uneven due to the following reasons:TopographyLatitudeClimate

TopographyThis refers to the slope of the Earths surface. Since the Earths surface is uneven, water naturally accumulates in areas with the lowest elevation.

If the Earth was perfectly smooth and spherical, the entire planet would be by water 1km deep!

TopographyMountains can also have a great effect on where rain falls. When moist air is pushed upwards as it travels over mountains it will condense and rain on one side of the mountain.

As the air moves over the mountain and down the opposite side, the air sinks and warms resulting in dry air on the other side of the mountain. This is called fohn wind. How do you think this affects environments?

TopographyAustralias Great Dividing Range has this effect which is partly why areas to the East of the range tend to be much wetter than those to the west.

LatitudeMany of the worlds deserts are located on or near the Tropics of Cancer and Capricorn and areas along the equator receive some of the highest rainfall. This is because of the convection of air in the atmosphere.

LatitudeThe air along the equator is hot all year and rises by convection. As the air rises it cools, creates clouds and high levels of rainfall. This air is then moved north or south and sinks as it cools. As it sinks, its warmed again and because its dry air clouds do not form. This is the reason why most deserts occur near the tropics.

ClimateClimate is an areas long term weather patterns and determines how much precipitation an area receives. Climate is influenced by latitude, topography, altitude, wind directions, ocean currents and proximity to oceans.

InterrelationshipsEarths systems are very complex and interconnected. A change to one system can impact others. For example, ocean currents are the main factor in the redistribution of heat around the world. This is called the great ocean conveyor belt.

InterrelationshipsDisruptions to this cycle could prevent the transfer of heat to higher latitudes. This would drop temperatures and build up ice around the poles. As a result sea levels would drop, and salinity of ocean water would increase. This would have a dramatic effect on coastlines.

See Figure 3.10 page 88 Prelim Spotlight TextInterrelationshipsChanges in one system can act as a trigger for changes in others. These can be positive or negative. Positive feedback amplifies a change to a system and cause it to increase in a snowball effect. Negative feedback cancels out changes in a system and promotes stable conditions.

Read the scenarios on page 89 Prelim Spotlight TextActivityComplete Activity 3.2 Prelim Spotlight Text page 89 together.ReviewThe GWB refers to the total distribution of water in all its forms and reservoirs on Earth. This distribution is uneven due to the following reasons:TopographyLatitudeClimate Earths systems are very complex and interconnected. A change to one system can impact others.Positive feedback amplifies a change to a system and cause it to increase in a snowball effect.Negative feedback cancels out changes in a system and promotes stable conditions.HomeworkRead pages 86-89 Prelim Spotlight TextUpdate electronic vocabularyComplete To Think About page 89 Prelim Spotlight TextComplete DOT Points 1.1-1,3