Elements, Minerals and Rocks

1. Elements, Minerals and Rocks

2. With this chapter we turn our attention to the Lithosphere. It is the earth’s surface which provides the ingredients from which life is formed and is the stage upon which the drama of life is played out. Over 70% of the Lithosphere is covered by the hydrosphere. The rocks that the Lithosphere contains tell the story of its multi-billion year past. The Lithosphere’s surface is ever changing. It is pushed and pulled by forces found in the interior of the earth and on the exterior. This presentation will deal with the makeup of the Lithosphere - the Elements, Minerals and Rocks!

3. The study of the solid earth is called: GEOLOGY. A ROCK can be defined as a combination of a variety of minerals in a solid state. A MINERAL is a naturally occurring, inorganic substance possessing a definite chemical composition and atomic structure. Think of a chocolate chip cookie as a rock. The cookie is made of flour, butter, sugar & chocolate. The cookie is like a rock and the flour, butter, sugar & chocolate are like minerals. You need minerals to make rocks, but you don't need rocks to make minerals. All rocks are made of minerals.

4. Minerals are made up of a variety of elements. An ELEMENT is a material that cannot be subdivided by ordinary methods into simpler materials. Elements are classified in the Periodic Table that you should be familiar with in Science. There are 91 natural occurring elements found in rock. These 91 elements can combine to form at least 2000 different minerals. The most common Minerals are: Plagioclase, Quartz, Orthoclase and Mica to name a few. The most common Elements are: Oxygen, Silicon, Aluminum, Iron and Calcium to name a few.

5. A vast number of minerals exist, together with a great number of their combinations into rocks. Some rocks are very simple to analyze, for example Diamonds are pure carbon (carbon is an element). Some composition of rocks are complicated, such as Granite. The next slide illustrates the makeup of Granite:

7. Most rock is extremely old, but rock is also being formed at this very hour as a volcano emits lava that solidifies on contact with the atmosphere. Rock can be classified into three categories depending on how they were formed: IGNEOUS SEDIMENTARY METAMORPHIC The majority of this presentation will deal with how each one was formed and giving some examples along the way. The final set of slides will illustrate THE ROCK CYCLE, which is a diagram that links the formation of the above types of rocks.

8. IGNEOUS • Igneous rocks are called fire rocks (or ‘born of fire’) and are formed either underground (Intrusive) or above ground (Extrusive). • Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks. • Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground.

10. Some examples of Igneous Rocks: Granite rocks are igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface. Granite is used for long lasting monuments and for trim and decoration on buildings. Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. This rock is so light, that many pumice rocks will actually float in water. Pumice is actually a kind of glass and not a mixture of minerals. Because this rock is so light, it is used quite often as a decorative landscape stone. Ground to a powder, it is used as an abrasive in polish compounds and in Lava soap.

11. Most Metallic Minerals such as Gold, Silver, Zinc, nickel, lead and copper are Intrusive igneous Rock. We find a lot of these minerals in the Canadian Shield.

12. SEDIMENTARY ROCKS • For thousands, even millions of years, little pieces (sediments) of our earth have been eroded--broken down and worn away by wind and water etc. • These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer (called Strata) after layer of eroded earth is deposited on top of each. These layers are pressed (Pressure is a key word) down more and more through time, until the bottom layers slowly turn or solidify into rock. • This strata can be folded, warped or cracked to form mountains like the Rockies. Remember the forces that do the folding are called Tectonic forces!

13. fossils are often found in sedimentary rocks, giving us clues to past life since we can accurately date the age of the rock in which the fossil was laid down. • Coal, oil and natural gas (fossil fuels) are found in sedimentary rock where large quantities of marine plants and animals in ancient seas were buried and partly decomposed as the sediments turned into rock. • Sediments made from broken rock are known as CLASTIC MATERIAL • Sediments made from chemical or organic material are known as N0N-CLASTIC or BIOGENIC. • Many Non-Metallic minerals such as Salt, Potash, Phosphate and Gypsum are sedimentary rocks

14. Pressure from overlying layers (strata)

15. Some Examples of Sedimentary Rocks: Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers as seen in this picture. They are often used as building stones. Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone.

16. Metamorphic Rock • Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks. • How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change. If you exam metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are. These flattened grains create layers or strata. • This banded structure called FOLIATION can help use differentiate a Metamorphic rock from an Igneous rock. (See the picture of Gneiss in following slides)

18. Some examples of Metamorphic Rock: Schist rocks are metamorphic. These rocks can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock. Gneiss rocks are metamorphic. These rocks may have been granite, which is an igneous rock, but heat and pressure changed it. You can see how the mineral grains in the rock were flattened through tremendous heat and pressure and are arranged in alternating patterns.

19. The percentage of the earth’s crust is made up of : 65% Igneous 8% Sedimentary 27%Metamorphic The process of replacing older rocks with new ones is called the Rock Cycle. The next slide illustrates this cycle:

20. The Rock Cycle: Source:http://geog.ouc.bc.ca/physgeog/contents/10a.html

21. The Importance of Rocks and Minerals Rocks and Minerals provide many of the raw materials used to manufacture a wide range of consumer items. The following are some examples or scenarios describing how important Minerals and Rocks are to our everyday life: 1: Southern Ontario is famous for the abundance of building materials found nearby. Sand and Gravel (aggregates) resulted from the last Ice Age. The Oak Ridges Moraine just north of Toronto is one such source. When the last great ice sheet started to melt and recede, the load of tiny grains and even large boulders that it was carrying were deposited. Much of this material was carried away by meltwater running through enormous spillways. Most of Southern Ontario was a depository for this sand and gravel.

22. 2: Another area in Southern Ontario where building materials are found in the Niagara Escarpment. The escarpment is the remains of an ancient sea bed that was raised by tectonic forces millions of years ago. The limestone found here is very resistant to erosion and is used for all kinds of construction. Other minerals used in construction are clay, gypsum, aluminum and graphite .

23. 3. Some of the minerals (intrusive) we use are very rare and therefore difficult to find. It is the work of geologist to find prospective mineral concentrations so they can be extracted from the earth’s crust. The basic questions a geologist must answer is: Is the mineral in sufficient quantity and concentration to mine profitably? If it costs more to extract than a company would make selling it, there there is no point in mining the mineral. World prices and Market demand also play a role. If these factors combine to make an ECONOMIC DEPOSIT will a company make an investment to open a mine.

24. Many economic deposits exist in the Canadian Shield and Western Cordillera part of Canada. These can be classified into three categories: Precious Metals: gold, silver, and platinum. Ferrous Metals (containing iron to make steel alloys): iron and nickel. Non-Ferrous Metals: copper, lead, and zinc, tin, aluminum and salt. The above minerals have made Canadian Mining Companies Internationally known.

25. 4. Oil and Natural Gas are two other valuable resources found in the earth. While these resources are fluid as opposed to solids like gold and iron, their extraction from the earth is also considered mining. Below is a brief outline of how Oil and Gas are created: • Occurred millions of years ago • Dead plants and animals called Plankton accumulated in shallow seas. • Plankton stores large quantities of carbon as CO2. • This CO2 was converted into carbohydrates by photosynthesis. • This fossilized sunshine was trapped in the sedimentary rocks that formed above it.

26. This layer of organic ooze decomposed very slowly because there was a lack of oxygen. • Bacteria transformed it into methane and a complex hydrocarbon called kerogen. If the temperature rose above 1000C, the kerogen changed into oil. • A concentration of oil occurs when the oil accumulates in spaces of porous (can be permeated by fluid or air) rock which are sandwiched by non-porous rock. See the diagram on the next slide. • The Athabasca Oil Sands found in Northern Alberta are interesting because the oil is not found in a neat reservoir but the oil is mixed with sand and shale. Extraction of the Oil Sands is difficult and costly.

27. The Athabasca Oil Sands: Source: Earth Matters, by Ron Chasmer, Oxford University Press.

28. 5. Coal is another valuable fossil fuel found in sedimentary layers. The following is a brief description of the formation a Coal: • Formed from living things • Giant forests grew in shallow tropical swamps • When the trees fell they decomposed slowly • Methane and peat (flammable organic substance) are formed • If the layers of peat were buried under sediments and heated, water vapour was squeezed out and coal is created • Coal, unlike oil is easily mined and does not need to be held in place by non-porous layers.

29. Formation of some popular minerals including coal: Source: Planet Earth, by Gary Birchall, John Wiley and Sons.

30. THE END!