Our Earth
Exploring our natural world

Glaciers & How Soil is Formed

Code D1: (DVD ONLY)

This DVD contains 2 programs

Program 1
Glaciers: Rivers of Ice

Glaciers are relatively recent phenomena as they appear to have existed only since the last ice age when cooler conditions began locking up large amounts of water into both continental and alpine glaciers. This uptake of water lowered sea levels around the world allowing humans to populate the continents. When these humans reached areas that had been under glaciation, they found fertile soils where plant and animal life abounded.

In this way glaciers have influenced human development in the past, as well as the landscapes we find in North America and Europe today.

The intricacies of glaciers are examined in some detail by this program. It looks at how glaciers form, the different types of glaciers that exist around the world and the distinctive landscape features created by present (or past) glaciers. Cirques, moraines and U-shaped valleys are among many that remind us of the awesome power of these slow-moving giants.

Although under threat today from global warming, the short history of glaciers makes it hard to generalise about the fate of today’s glaciers. However what is certain is that if the glaciers do melt then many of our coastal cities will resemble classical Atlantis as rising sea levels envelope them.

Program 2
How Soil is Formed: from Rocks to Riches

Soils are the final result of the long and slow processes that weather the exposed rocks in our landscape. As far as the transformation of rock into soil is concerned, its all down-hill as the agents of erosion and gravity take their toll.

The various forms of weathering that can lead to the formation of soils are broken down into three main areas: Physical Weathering; Chemical Weathering and Mass Movement.

Physical Weathering includes frost action, the pressure of tree roots and the buckling and cracking of rocks that have had pressure removed from them. As the name suggests, Chemical Weathering involves the mixing of chemicals to produce compounds that accelerate the weathering process. A good example of this is the weak Carbonic Acid in rainwater that causes damage to many of the stones, not only in our landscape, but also in our public buildings as well. Finally the process of Mass Movement whereby rocks and soil are moved form higher altitudes to lower altitudes also accelerates the transformation of rock into soil.

This program finally examines why different types of soil form and why soil formation occurs at different rates around the world.

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Wind Erosion & Water Erosion

Code D2: (DVD ONLY)

This DVD contains 2 programs

Program 1
How wind shapes the world

The ancient Greeks listed the four elements as Earth, Air, Wind and Fire. In this program we see how wind is a constant engine of change around the world.

Over one third of the earth’s surface is desert, either the well-known sandy deserts, or the polar ice caps. Why this is so is directly attributable to the prevailing winds.

Initially created in the hot-house of the tropics when warm, moist air rises, the wind is twisted and funnelled by the earth’s rotation to create the wind currents we have today.

On a global scale this leaves two areas with low chance of rain; areas between 20 and 30 degrees north and south of the equator, and the polar regions. These are where we find most of today’s deserts.

Although created by global winds, these dry regions are also shaped by local winds that create sand dunes and fantastically eroded landscapes.

Even today with all our technology, the wind still selects the places where most of us live.

Program 2|
How Water Shapes the Earth

Water is an essential part of our lives and a valuable resource. It also enriches our lives with its sheer beauty.

Water is one of the world’s most abundant resources although much of it is in the form of salt-water in oceans or locked up in the polar ice caps and in glaciers.

But the system is not static, polar ice melts and ocean waters evaporate to keep the system in a continual cycle that brings water from the ocean to the land and back to the ocean again.

This water cycle brings water to the land in the form of rain or snow. Once deposited this water begins its slow transformation of the land across which it travels. Some seeps into groundwater, to emerge as a spring kilometres away, while other water becomes runoff and makes its way into streams and rivers.

These streams and rivers have a hierarchy of forms from the youthful stream in its steep V-shaped valley through to the old river full of meanders and swamps.

Of all water perhaps the most valuable is groundwater because of its ability to deliver water to places that may not have sufficient rainfall. In aquifers this water can travel many kilometres before it is pumped out into an artesian well or naturally comes to the surface in the form of a spring.

All this movement of water also leaves its mark on the earth’s surface as water erosion is one of the more forceful around. With floods and gradual river erosion, water has largely presented us with the world as we see it today.

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Plate Tectonics, Volcanoes & Earthquakes

Code D3: (DVD ONLY)

This DVD contains 3 programs

Program 1

This program examines the history of the theory of plate tectonics and mechanisms of continental shift that shape the world around us.

In the early twentieth century enough evidence from around the world had been compiled to make some people believe that the world’s continents had not always been at their present location.

The boundaries of continents seemed to match up like a jigsaw puzzle, while similar plants and animals were found in Australia and South America; now separated by ocean. Even mountain ranges and particular strata of rock were found to be continuous from one continent to another.

Led by German thinker Alfred Wegener, the theory of Plate Tectonics gradually developed. This theory held that the earth’s crust is divided into many plates, some oceanic, some continental, that all move independently of each other. Like a skim on milk, the continents are now understood to float on the molten mantle, pushed this way and that by convection currents within the mantle. The lighter plates such as the large, but oceanic Pacific Plate, move as much as 25 mm a year.

When these plates collide or interact the geological fun begins. At some divergent plate boundaries, plates move apart and new mountain ranges are being formed. At other convergent boundaries, two plates collide with one being forced to slide under the other. Still a third form of fault is the transform boundary where two plates slip along side each other. Each of these plate boundaries have the potential to produce volcanoes and earthquakes, but the convergent boundaries that characterise the Pacific’s ‘Ring of Fire’, are the most unpredictable and dangerous.

The process of Plate Tectonics is still under way, albeit very slowly. Inevitably Australia will drift north, the Himalayan Mountains will continue to rise, San Francisco will be on an offshore island and east Africa will also be an island, torn off from the African continent.

Program 2

This program explores what causes volcanoes, how magma makes its way to the surface and how plate boundaries, subduction zones and hot spots influence their occurrence.

While Australia may only have one active volcano (Big Ben on Heard Island), we are nearby to countries such as Papua New Guinea which rest on the Pacific Ocean’s ‘Ring of Fire’. At places like Rabaul in New Britain, volcanoes are a constant factor of life and only recently new volcanic sea mounts have risen out of the water in the town’s harbour.

Volcanoes can occur at divergent faults between tectonic plates; such as the mid-ocean ridge where new rocks and mountains are being created everyday. This zone circles the globe and includes the island nation of Iceland whose many volcanoes and hot springs are testimony to the volcanic activity created in this zone.

Volcanoes can also occur at subduction zones and many of the Pacific Rim volcanoes fall into this category. Like those at Rabaul, the volcanoes in our region are created when the more-dense Pacific Plate is forced under the less-dense Indo-Australian Plate. As a result, a line of volcanoes such as those at Rabaul is created.

At other places, hotspots are formed in an area of weakness in the earth’s surface, allowing magma to come near to the surface.  Yellowstone National Park and the Hawaiian Island chain are both examples of hotspot volcanic activity.

While the volcanoes themselves come in the three major varieties of Shield, Cinder Cone and Composite Volcanoes, the types of explosions that can issue from these volcanoes is varied and depends on many factors. From the super-fast Plinian explosion to the soft rolls of pillow lava that form under water, volcanic eruptions can come in all shapes and sizes.

Due to their size, majesty and destructive powers, volcanoes are frequently studied by vulcanologists, but research into how to predict eruptions is still in its infancy and new discoveries concerning volcanoes are being made everyday.

In 1993 for example, scientists working at mapping the sea floor in the South Pacific Ocean discovered a vast field of volcanoes towering 2,500 metres above the sea floor. Of the 1133 volcanoes mapped, two or three could be erupting at any time and the discovery underlies that we still have much to learn about the processes and mechanisms of volcanoes.

Program 3

This program is an in-depth look at what causes earthquakes and how we can predict when earthquakes will strike.

Earthquakes are one of the more poorly understood natural disasters that periodically affect people around the world.

Recently in China, Iran, Turkey and many other countries, the devastating effect of earthquakes have been felt. These events can decimate communities and obliterate towns; often towns that have stood impregnable for hundreds of years.

Naturally, due to the appalling loss of life and property caused by earthquakes, a lot of effort has been devoted to understanding how earthquakes occur and how it might be possible to predict the arrival of major earthquakes.

Not until the theory of plate tectonics was advanced did people have any hope of understanding the origins of the enormous amounts of energy seen in earthquakes. Now, with highly accurate instruments, many based in space, seismologists can map the minute movements of the many plates that comprise the earth’s crust.

At the boundaries of these plates several things can happen. If one plate buckles and rises against another plate a normal fault is created and the resulting earthquakes tend to be small. When two plates slide along side each other to create a strike-slip fault, the resulting earthquakes also tend to be small. But when one plate is forced under another in a reverse, or thrust, fault, severe earthquakes can result.

While earthquakes might originate in three major ways, they all have common features such as hypocentres, epicentres and seismic waves. Our knowledge about these features has increased along with the science for recording and mapping the many earthquakes of different magnitude that affect the world each day.

While the science of recording earthquakes is well advanced, the science of predicting earthquakes is a very imprecise science. However, as long as earthquakes continue to be a threat to both life and property, scientists from around the world will work at ways for allowing us to better understand the tremendous forces of earthquakes, and perhaps, to predict or prevent the Big One!

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Our Atmosphere & Our Rivers and Oceans

Code D4: (DVD ONLY)

This DVD contains 2 programs

Program 1

This program explores the earth’s atmosphere; an essential belt around the globe that sustains all living things.

Primarily consisting of Nitrogen (71%) and Oxygen (28%), the atmosphere also has trace amounts of many other gasses including Argon and Carbon Dioxide. 85% of these atmospheric gasses are found in the dense troposphere, the atmosphere’s lowest layer. This is also the layer we alter with our pollutants and greenhouse gasses.

Above the troposphere is the stratosphere where ozone traps much of the ultraviolet radiation that is continually bombarding the earth.

Still higher is the ionosphere where solar radiation interacts with air molecules in the upper atmosphere to create many layers of ions.

This layer cake arrangement is fluid as the earth’s atmosphere redistributes the sun’s heat around the globe. As this happens, warm air rises causing low pressure air masses, and cold air descends to form high pressure air masses. As these air masses collide, local weather is formed either in the form of high vertical storm clouds in advance of a cold front, or wispy Cirrus clouds in advance of a warm front.

The thankless task of trying to forecast the weather falls to meteorologists who sometimes accurately predict the onset of severe weather that saves many lives.

Program 2

This program explores the earth’s water, one of the world’s most abundant resources; although much of it is salt-water in our oceans or ice; frozen solid in the polar ice caps and within alpine glaciers.

However, the Hydrologic system is not static, polar ice melts and ocean waters evaporate to keep the system in a continual cycle that brings water from the ocean to the land and back to the ocean again.

After falling on the land in the form of rain or snow, this water begins a slow transformation of the land across which it travels. Some seeps into groundwater to emerge as a spring kilometres away, while other water becomes runoff and makes its way into streams and rivers.

Ultimately the water ends up in the oceans that cover 71% of the earth’s surface. These oceans have been salty for a long time, probably since they were first created. The oceans’ salinity comes from dissolved salts being washed from the land and from volcanic gasses, especially from the large number of volcanoes that continue to be active beneath the sea.

Due to the constant shifting of the earth’s plates, the ocean floor provides stunning examples of towering mountain ranges and dizzying chasms; at a scale dwarfing anything found on dry land. Even the world’s longest mountain range, the mid-ocean ridge, is largely concealed beneath the ocean’s waves.

With most of the earth’s water tied up in ice or oceans, only a small proportion is left as fresh water in our rivers, lakes and groundwater. Of this, not all is useable by humans as a mere 0.03% of all the world’s water is easily accessible as fresh drinking water. This makes water the world’s most abundant, but precious, resource.

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Our Universe & Our Planet Earth

Code D5: (DVD ONLY)

This DVD contains 2 programs

Program 1

The facts and figures used to describe our universe are so mind-numbingly large that they defy normal human comprehension. The universe itself is billions of years old and contains billions of galaxies, that in turn, contain billions of suns and solar systems. Our sun is a million times bigger than our earth, while a red giant star is many million times larger than our sun. The nearest star to our own is light years away and everything seems to be speeding away through space as a result of the Big Bang.

As awesome as the universe is, we are forced to view it from an earth-bound vantage point. Our closest neighbour is our moon that orbits the earth just as we orbit the sun, and as our solar system orbits the centre of our galaxy, the Milky Way. This clockwork precision is due to the forces of gravity and inertia that affect all bodies in the universe.

A little further out from the moon are the other eight planets that constitute our solar system. From the inner, smaller, rocky planets such as our own, to the outer gaseous giants such as Jupiter, all the solar system’s planets were probably formed at around the same time as a gas and dust cloud coalesced into our sun and the various planets.

Further out from our solar system lie countless galaxies and suns. These suns range from stable yellow suns such as our own through to super-hot blue suns and cooler red suns. Just like living things, all suns have a life cycle that includes birth and death, often with spectacular results. When a sun has consumed all its energy it expands rapidly to become a red giant. With time the gravitational forces at work will force the red giant to collapse in on itself to form either a super-dense white dwarf or to create a spectacular explosion, or supernova, that can give off the energy of a million suns.

We are only just starting to understand how our universe was formed and how it operates. As research continues in this field, expect many more discoveries about where we have all come from and what the ultimate future of our earth and solar system will be.

Program 2

This program shows how our planet earth is slowly revealing its mysteries to us - but this understanding is only recent.

First outlined by German thinker Alfred Wegener, the theory of Plate Tectonics is now accepted. This theory holds that the earth’s crust is divided into many plates, some oceanic, some continental, that all move independently of each other. Like a skim on milk, the continents are now understood to float on the molten mantle, pushed this way and that by convection currents within the mantle. The lighter plates such as the large, but oceanic Pacific Plate, move as much as 25 mm a year.

Even today we can only theorise on how this process works. Geologists envision the earth having a super-hot, but solid core, a molten outer core, then the semi-molten mantle and finally the solidified crust. Within this mix are rocks and minerals; many of which are exploited by humans for various purposes.

While minerals, a material with a unique chemical composition, and rocks, a mixture of two or more minerals, have the same origins, they are classified differently. Minerals are described in terms of their physical properties such as strength or lustre. Rocks, on the other hand, are classified by the method in which they were made. With unique histories, the three main forms of rock, igneous, sedimentary and metamorphic, are the basis of all rocks we have on earth.

The study of the earth’s rocks and minerals inevitably leads to questions about the history of the earth. Especially since fossils can be used to illustrate past environments, as well as the age of the rock in which that were found. In this way the four major geological era, the Precambrian, Palaeozoic, Mesozoic and Cenozoic are characterised by different forms of life slowly evolving over a vast geological time scale.

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