WORLD OF ROCKS -1
It is being guessed that earth, one of the 9 planets arroud sun, is 4,6 billion years old. Humans live on earth since the last 50.000 years of this period. And human being have been in touch with rocks from the primitive man to todays modern community. They built their houses by using rocks from their first houses which are the cavities in the rocks (caves) to todays skyscrapers. They used rocks as kitchenware, hand tools, decorative purposes. They even carried rocks on them as jewellery. Even the historical ages are named by rocks.
Today, rocks are being used not only for decorative and functional purposes but also in mining, construction and infrastructure as one of the raw materials. If we look at the rocks in detail;
The outer shell of the earth, up to 16-30 km in depth, is called as crust. The 75% of crust is made of only 2 elements (Oxygen 46,6% and Silica 27,7%) where 99% of crust is made of 8 elements. (addtional to oxygen and silica, aluminum 8,1%, ferrous 5%, calcium 3,6%, sodium 2,8%, potasium 2,6%, magnesium 2,1% and other elemets 1,5%)These elements forms the minerals, the fundamental material of rocks. Ther are about 2,000 different minerals on earth. But only 10 of them is important for rock forms.
Rocks are described as the aggregate of one or several minerals, forming the great mass of earth’s crust.the solid accumulations formed by one ore more minerals. Basically there are 3 types of rocks. Magmatic (igneous), Sedimentary and metamorphic. The 95% of rocks are magmatic where 4% are metamorphic and 1% are sedimentary.
WORLD OF ROCKS - 2
Magma is silica paste in liquid form. Magmatic rocks are formed by cooling and solidifying of molten magma on earth or in deeper layers of earth crust. Magmatic rocks are generally crystalised masses. There are two types of magmatic rocks:
Giant’s Causeway: When the basaltic lava gets cool, usually columns of hexagonal shape are formed. Giant's Causeway in Nortehrn Ireland is a very typical example for this event.
1.Plutonic (intrusive) rocks Plütonik
Plutonic rocks are formed by cooling of magma in deep crust before the magma reaches to the earth surface. Magma gets cool slower in deep. Due to this slow cooling, they present large crystals, with phaneritic textures. The most common plutonic rock is granite. Additionally diorite, syenite and gabro are examples of plutonic rocks.
Granite: The most common intrusive rock is granite. Basically granite contains quartz, mica and feldspat. Usually it has a spotted view. Granite has different colors from gray to red depending on the percentages of the minerals in it.
2. Volcanic (extrusive) Rocks Volkanik (Püskürük) Kayaçlar
Volcanic rocks are formed by cooling of magma on earth surface. Since the magma reaches the earth surface, cooling is fast. Because of fast cooling, volcanic rocks have small crystals and have a glassy view. Basalt is the most common volcanic rock. Aloe andesite and obsidian are examples for volcanic rocks.
Basalt Bazalt: Basal, the most common volcanic rock, is formed by solidified lava. It has a very hard structure.
Obsidien Obsidyen: Obsidien forms by very fast cooling of lava. Because of this formation, it can be classified as a derivative of glass. Obsidien was used as a cutting tool by old humans because of its typical hard structure and sharp edges.
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Grand Canyon: The grand canyon in America is a very typical example for sedimentary rocks. It is formed by abrasion of limestone and red sandstone.
Sedimentary rocks, as can be understood by its name, are formed by precipitation of substances. The present rocks are abraded and worn away by outer factors such as wind, rivers, sun, waves. By this, small rock particules and minerals accumulate. These precipitations are moved usually to river beds of seas in time and accumulate. These precipitations get squeezed under the accumulations and with this pressure, volumes get smaller, pores go away and the water content discarded. By these effects and chemical reactions minerals are formed. These minerals and the organic substances in the precipitation behaves as cement and the precipitation gets aharder and becomes rock in long times, even millions of years. There are 3 different typrs of sedimentary rocks. Chemical, organic and physical (clastic).
Limestone: The most common sedimentary rock is limestone. It contains calcium carbonate. It is used for lime and cement production.The rocks containing at lease 90% of calcium carbonate are called as limestone.
1.Chemical Sedimentary Rocks
Some of the sedimentary rocks are formed by evaporation of salty water and precipitation of rich solutions. The most common known chemical sedimentary rock is limestone. Other examples are gypsum, dolomite and halite(rock salt).
Gypsum: Gypsum is used for production of plaster. Gypsum and rock salt are generally found in old sea basins where the sea water evaporated.
2. Physical (Clastic) Sedimentary Rocks
Phsical sedimentary rocks are formed by precipitation of mineral in river beds and basins. Sandstone, slate and conglomera are typical examples.
Conglomera Konglomera: The pebbles in this rock are rounded by the water. Then they get binded eachother and form conglomera.
Sandstone Kumtaşı: Sandstone is formed by the binding of small sand particules. In deserts, the sandstone has a red color where the quartz minerals ara abrased and rounded by wind.
3. Organic Sedimentary Rocks
Organic sedimentary rocks are formed by deposit and degenesis of organic substances (Remais of organisms such as sponge, coral, alg and plant remains). Coal, coral islands and chalk are examples of organic sedimentary rocks.
Anthracite: Anthracite is the highest quality coal. It is much harder than other coal types and do not paint hand when touch. It contains more carbon from all other coal types. Due to this property, it gives more heat, smokes less and it is the most valuable coal.
WORLD OF ROCKS – 4 TAŞLARIN DÜNYASI - 4
Metamorphic rocks are formed by metamorphism of magmatic or sedimentary rocks. The main metamorphism agents are pressure and heat. Magma forces the undergraound rock layers in order to reach the earth surface. During this event, the rock masses arround this magma are affected by heat and pressure. Marble from limestone, diamond from coal are examples for this metamorphic rocks.
Marble: In fact marble is a metamorphic limestone. But the name “marble” is also used for other types of rocks in rock industry. Marble is used for decorative purposes with its attractive structure, easey cutting and shining properties. .