1)Formation of Soilsl From Rocks

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FACTORS OF SOIL FORMATION

Soi1 scientists recognize five major factors that

influence soil formation:

1) parent material (rocks, organic materials),2) climate,

3) living organisms (especially native vegetation),

4) topography and

5) time. The combined influence of these soil-forming

factors determines the properties of a soil and

their degree of expression

The combined influence of these soil-forming factors

determines the properties of a soil and their

degree of expression


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FORMATION OF IGNEOUS ROCKS1 2 3

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What are igneous rocks and how are they formed?Igneous rocks are called fire rocks and are formed either underground or above

ground. Underground, they are formed when the melted rock, called magma, deep

within the earth becomes trapped in small pockets. As these pockets of magmacool 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.

OR

Igneous rocks (from the Greek word for fire) form when hot, molten rock (magma)

crystallizes and solidifies. The melt originates deep within the Earth near active

plate boundaries or hot spots, then rises toward the surface. Igneous rocks are

divided into two groups, intrusive or extrusive, depending upon where the molten

rock solidifies.


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Intrusive Igneous Rocks:

Intrusive, or plutonic igneous rock forms when magma is trapped deep inside the Earth.

Great globs of molten rock rise toward the surface. Some of the magma may feed

volcanoes on the Earth's surface, but most remains trapped below, where it cools very

slowly over many thousands or millions of years until it solidifies. Slow cooling means the

individual mineral grains have a very long time to grow, so they grow to a relatively large

size. Intrusive rocks have a coarse grained texture.

Extrusive Igneous Rocks:

Extrusive, or volcanic, igneous rock is produced when magma exits and cools outside of,

or very near the Earth's surface. These are the rocks that form at erupting volcanoes and

oozing fissures. The magma, called lava when molten rock erupts on the surface, cools

and solidifies almost instantly when it is exposed to the relatively cool temperature of the

atmosphere. Quick cooling means that mineral crystals don't have much time to grow, so

these rocks have a very fine-grained or even glassy texture. Hot gas bubbles are oftentrapped in the quenched lava, forming a bubbly, vesicular texture. Pumice, obsidian, and

basalt are all extrusive igneous rocks.


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TYPES OF IGNEOUS ROCKS

1. Granite rocks are igneous rocks which were formed by slowly cooling pockets of

magma that were trapped beneath the earth's surface. (intrusive)

2. Scoria rocks are igneous rocks which were formed when lava cooled quickly aboveground. You can see where little pockets of air had been. Scoria is actually a kind of glass

and not a mixture of minerals.

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Obsidian rocks are igneous rocks that form when lava

cools quickly above ground. Obsidian is actually glass

and not a mixture of minerals. The edges of this rock

are very sharp

Pumice rocks are igneous rocks which were formed

when lava cooled quickly above ground. You can seewhere 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


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Andesite is a fine-grained, extrusive igneous rock composed mainly of plagioclase with other

minerals such as hornblende, pyroxene and biotite. The specimen shown is about two inches (five

centimeters) across.

Basalt is a fine-grained, dark-colored extrusive igneous rock composed mainly of

plagioclase and pyroxene. The specimen shown is about two inches (five



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Diorite is a coarse-grained, intrusive igneous rock that contains a mixture of feldspar, pyroxene,

hornblende and sometimes quartz. The specimen shown above is about two inches (five


Gabbro is a coarse-grained, dark colored, intrusive igneous rock that contains feldspar, augite

and sometimes olivine. The specimen shown above is about two inches (five centimeters)

across.


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Granite is a coarse-grained, light colored, intrusive igneous rock that contains mainly quartz

and feldspar minerals. The specimen above is about two inches (five centimeters) across.


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FORMATION OF SEDIMENTARY ROCKS

For thousands, even millions of years, little pieces ofour 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, untilthe bottom layers slowly turn into rock.


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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 buildingstones.


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Limestone rocks are

sedimentary rocks that are

made from the mineral

calcite which came from

the beds of evaporatedseas and lakes and from

sea animal shells. This rock

is used in concrete and isan excellent building stone

for humid regions.


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Shale rock is a typeof sedimentary rock

formed from clay

that is compacted

together by pressure.

They are used to

make bricks and

other material that isfired in a kiln


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Gypsum rocks are

sedimentary rocks madeup of sulfate mineral

and formed as the result

of evaporating sea waterin massive prehistoric

basins. It is very soft and

is used to make Plaster

of Paris, casts, molds,

and wallboards


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Metamorphic rocks are rocks that have "morphed" intoanother 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.


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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.

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1)Formation of Soilsl From Rocks