Houideg Athmane Geologist Engineer

Have you tried to guess the Earth’s age?

This world is far older than you can gage. Try, if you to count to four billion, then add an other six hundred million. Earth is older than you can see any river, mountain, valley, or tree.

Mother Earth is four thousand, six hundred million years old (4,600 million = 4.6 billion), give or take a few hundred million years.

It is older than anything you can see around you.

The age of Earth is so long compared to all periods of time that we humans are familiar with, it has been given a special name: Geologic time.

The age of Earth is as vast in time as the universe is vast in space. It is not easy to really get a "feel" for 4,600 million years! One way to try to get a "feel" for how big it is, is to break the number down into smaller pieces that perhaps we can understand. Just for fun you might try the activity, "What is a Million?" Then try to think about 4,600 million!

Houideg Athmane Geologist Engineer

The

Stai

rway

of T

ime

The odd names of the different time periods on the Staircase of Time were made up by geologists, who were the first people really interested in finding out the actual age of the Earth. Most of the names have to do with places where certain types of fossils were found.

Here we use another comparison to help show the span of time since the formation of Earth:

Houideg Athmane Geologist Engineer

How Old is That Rock? • How can you tell the age of a rock or to which geologic time period it

belongs? One way is to look at any fossils the rock may contain. If any of the fossils are unique to one of the geologic time periods, then the rock was formed during that particular time period. Another way is to use the "What's on top?" rule. When you find layers of rocks in a cliff or hillside, younger rocks are on top of older rocks.

• But these two methods only give the relative age of rocks which are younger and which are older. How do we find out how old a rock is in years? Or how do we know how long ago a particular group of fossilized creatures lived?

• The age of a rock in years is called its absolute age. Geologists find absolute ages by measuring the amount of certain radioactive elements in the rock. When rocks are formed, small amounts of radioactive elements usually get included. As time passes, the "parent" radioactiv

• e elements change at a regular rate into non-radioactive "daughter" elements. Thus, the older a rock is, the larger the number of daughter elements and the smaller the number of parent elements are found in the rock.

Houideg Athmane Geologist Engineer

• A common "parent-daughter" combination that geologists use is radioactive uranium and non-radioactive lead. As shown in the diagram at right, uranium is trapped in a newly formed rock. As the rock ages, more and more of the uranium changes into lead.

• The age of the rock in years can be found by measuring the rate at which a parent element decays and then measuring the ratio of parent element to daughter element in the rock. The ages in years of the different geological time periods are found by measuring the absolute ages of many rocks from all of the different periods. The absolute ages of some of the different geologic time periods are shown along the right side of the Staircase of Time.

• The steps of the Staircase of Time are drawn to be almost the same size, so you might think that the time periods are the same length, but they are not. The absolute ages of rocks taken from the different time periods have shown that the time periods were of greatly differing lengths. Some were very short, like the Quaternary period (only 2 million years), while others were very long, like the Proterozoic Era (almost 2 billion years). According to absolute-age measurements.

Houideg Athmane Geologist Engineer

Minerals are defined as naturally occurring, inorganic, solids with a definite chemical composition and a regular, internal crystalline structure.

- Hardness is one of the better physical properties for minerals- Hardness is one measure of the strength of the structure of the

mineral relative to the strength of its chemical bonds- Hardness can be tested through scratching. A scratch on a

mineral is actually a groove produced by micro fractures on the surface of the mineral

- A harder substance can only scratch a mineral. A hard mineral can scratch a softer mineral, but a soft mineral cannot scratch a harder mineral (no matter how hard you try). Therefore, a relative scale can be established to account for the differences in hardness simply by seeing which mineral scratches another. That is exactly what French mineralogist Friedrich Mohs proposed almost one hundred and seventy years ago.

Houideg Athmane Geologist Engineer

For thousands, even millions of years, little pieces of our earth have been eroded-broken down and worn away by wind and water.

These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock

Houideg Athmane Geologist Engineer

Argillaceous Rocks Shale - Clay - Claystone - marl Carbonate Rocks Limestone - Dolomite - Chalk Siliceous Rocks Siltstone - Sand - Sandstone - Chert

- Conglomerate

Evaporites Rocks Gypsum - Anhydrite - Halite

Organic Materials Coal - Lignite - Bituminous Minerals

Houideg Athmane Geologist Engineer

1-Talc 2- Gypsum 3- Calcite 4- Fluorite 5- Apatite 6- Orthoclase 7- Quartz 8- Topaz 9- Corundum (ruby and sapphire) 10- DiamondTo remember the Mohs scale try remembering this phrase:The Geologist Can Find An Ordinary Quartz, (that) Tourists Call Diamond!

Physical Property

Definition Testing Method

COLOUR Visible light spectrum radiation reflected from mineral

Look at the sample and determine its colour - white, black, green, clear, etc.

HARDNESS Resistance to scratching or abrasion

Use minerals of known hardness from the Mohs Hardness Kits. Scratch the unknown mineral with a known hardness to determine which mineral is harder. Continue doing this with harder or softer minerals from the kit until the hardness is determined. 

REACTION to HCL

Chemical interaction of hydrochloric acid and calcium carbonate (CaCO3)

Place one small drop of HCL on a sample a watch for a reaction - effervesces (bubbles)

Houideg Athmane Geologist Engineer

Composition

are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells

Characteristics

Limestone rocks are sedimentary rocks, his rock is used in concrete and is an excellent building stone for humid regions, Limestone dissolves in rainwater more easily than other rocks

Colour Black Pink - Brown White - Grayish - Green Translucent

Hardness Soft Firm - Friable - Indurate - Brittle

Houideg Athmane Geologist Engineer

CaMg(CO3)2

Composition

Ca: Calcium = 21.73 % Mg:Magnesium =13.18 %

C:Carbon =13.03 % O:Oxygen = 52.06 %

Characteristics

Reacts to HCL in its powdered form, similar properties to calcite, is similar to that of calcite, with alternate layers of calcium ions totally replaced by magnesium. This ordered arrangement of cations slightly impairs the overall symmetry of the structure but is essential to the stability of the mineral, Chemically and structurally it may be regarded as calcite with half the calcium ions replaced by magnesium , Dolomite in addition to the sedimentary beds is also found in metamorphic marbles,

hydrothermal veins and replacement deposits Colour White, Gray, Reddish white, Brownish white, Gray

Hardness 3.5 - 4

Density (g/cc) 2.8 - 2.9

Houideg Athmane Geologist Engineer

FeS2

CompositionFe: Iron = 46.55%

S2:Sulfur = 53.45%

Characteristics

"Fool's Gold“; abrasive, magnetic after heating, could be: sedimentary, magmatic, metamorphic, and hydrothermal deposits, not Radioactive, very dangerous on bits if shown as cement between Sandstone grains, but less dangerous if shown as nodules inclusions in Claystone

Colour gold metallic colour or Creamy white

Hardness 6.5Density (g/cc) 5.01

Houideg Athmane Geologist Engineer

SiO2

Composition

Si: Silicon = 46.74 %

O: Oxygen =53.26 %

Characteristicsis typically white or clear, abrasive, Sedimentary, metamorphic, and igneous rocks, not Radioactive

Colour Clear, Transparent, Translucent, Vitreous, white, Brown, Colourless, Violet, Gray, Yellow

Hardness 7(Mohs scale ), Hard to very hard

Density (g/cc) 2.6 - 2.65

Houideg Athmane Geologist Engineer

Ca(SO4) (Calcium Sulphate)

Composition Ca:Calcium = 29.44 % , S:Sulfur = 23.55 % O:Oxygen = 47.01 %

Characteristics

A member of the evaporite group of minerals and the soft rock comprising anhydrite, formed by precipitation of Calcium Sulphate from evaporation of seawater, also after dehydration of Gypsum, Anhydrite can also form through the dehydration of gypsum, another sulphate mineral found in evaporites, Anhydrite may occur as a cap rock above salt domes,

Colour milky, grey, white

Hardness 3.5 poorly indurate to moderately indurate, firm, well compacted

Density (g/cc) 2.97

Houideg Athmane Geologist Engineer

Composition Grains of Quartz and Feldspar

CharacteristicsSandstone 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

Colour grey,white, yellowish, clear, transparent and translucent

Hardness moderate indurate to well indurate, friable, could be moderately hard to very hard

Houideg Athmane Geologist Engineer

Composition Is made of finer grains of Quartz and Feldspar

CharacteristicsSilt is a size term used for material that's smaller than sand (generally 0.1 millimeter), The field test for siltstone is that you can't see the individual grains, but you can feel them. Many geologists rub their teeth against the stone to detect the fine grit of silt

Colour brown, grey,white, yellowish Hardness moderate indurate to well indurate, friable,

could be moderately hard

Houideg Athmane Geologist Engineer

Composition Contains at least 50% of Aluminium Silicate, results to the decomposition of rocks rich in Feldspar, adsorb water to form a sticky material

CharacteristicsShale rock is a type of sedimentary rock formed from clay that is compacted together by pressure. They are used to make bricks and other material that is fired in a kiln; impermeable

Colour black, occasinally brown, orange, dark grey, dark

Hardness Plastic, soft, firm, hard, brittle, compacted to moderately compacted