bedrock geology c.c - stanley ppt

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Bedrock Geology C.CStanley Ta

Mr. Young 3rd

2/25/11



Atomic arrangement of minerals.

The atomic arrangement of minerals can affect the property of itbecause the atoms inside minerals are arranged differently. Theunique arrangement of the atoms inside a mineral varies frommineral to mineral. This changes the property and shape of mineralcrystals.

The arrangement of atoms inside a crystal structure can bedescribed by its unit cell, which is a small box containing a uniquearrangement of atoms.

In the example of the diamond and coal minerals, the arrangementof atoms results in diamonds crystallizing in the cubic system, while

coal crystallizes in the hexagonal system. This causes thedifference in structure between the two, despite the fact that bothare made of carbon atoms.

Another term for the atomic arrangement of minerals is orderlycrystalline structure.



Hardness

Hardness is a reliable physical property for mineral identification. It

is a measure of the physical strength of the mineral relative to the

strength of the mineral¶s chemical bonds.

Usually, minerals with tightly packed, small atoms with strong

chemical bonds are the hardest minerals. The hardness of a mineral can be tested through scratching. A soft

mineral cannot scratch a harder mineral, therefore, minerals can

only be scratched by minerals harder than itself. Because of this, the

Mohs Hardness Scale was created by Friedrich Mohs.

The scale starts with talc at 1 and ends with diamond at 10. Thehigher the number, the harder the mineral. The lower the number,

the softer the mineral.



Luster

Luster is a description of how much of a mineral¶s surface reflectslight. It can also be an explanation of the way light interacts andreflects with a crystal¶s surface.

Luster isn¶t relative to color or shape, but rather transparency,crystal habit, surface conditions, and index of refraction.

General terms used to describe luster in minerals include metallic,nonmetallic, and waxy.

Minerals that are metallic are reflexive and opaque, for example,gold.

Minerals that don¶t look like metal at all are classified as non-

metallic. Non-metallic luster has many sub-types, such asadamantine, silky and dull.

Minerals that are waxy have the look of wax, an example of thiswould be turquoise.



Cleavage

A mineral¶s cleavage is how it breaks along even and flat surfaces.

Different types of cleavage are shown because different minerals

break in different ways.

Minerals may break along cleavages. Some of them in one, two, or

three directions. Minerals such as quartz, has no cleavage. Cleavage can be described as perfect, good, or poor/imperfect.

A mineral¶s fracture is related to its cleavage. Fracture is breakage

that is not flat, but more rigid and shaped.

The two general, main types of fracture are conchoidal and uneven.

Minerals that are metallic might have a hacky fracture, which meansjagged.



Color

The distinctive color from a mineral can be used for identification.

Color can be fairly reliable in metallic and opaque minerals.

In translucent or transparent minerals, color should not be the only

type of classification you should use. The color of translucent or

transparent minerals are usually from chemical impurities, whichcould lead to an incorrect identification.

It is very important to be as precise as possible when classifying

with color. Also, the surface of a mineral could be weathered, so it is

crucial that you examine the mineral in good light.



Streak

Streak is the color of the powder created from a finely crushed

mineral. The true color of minerals can be shown from their streak.

Streak is a more reliable property for identification then color,

because of the more accurate process.

The process of crushing a mineral may remove some impurities andflaws.

Metallic minerals appear dark in streak because the particles absorb

the light instead of reflecting them, which is the case in non-metallic

particles. This is why the streak of metallic minerals is dark and the

streak of non-metallic minerals is light.



Diagram.



Igneous rocks.

Igneous rocks come from the magma deep below the Earth¶s crust.

When the liquid is pushed out toward the surface, it cools and turns

into an igneous rock. Igneous rocks are older than metamorphic and

sedimentary rocks.

There are also different types of igneous rocks. Intrusive igneousrocks are igneous rocks that cool underneath the earth¶s surface

from shallow magma. Intrusive igneous rocks usually cool slowly.

Extrusive igneous rocks are igneous rocks that are igneous rocks

that were formed when magma erupted from a volcano and turned

into lava. When the lava cools, it forms rocks with tiny crystals.These are extrusive igneous rocks, which usually cool very fast.

Igneous rocks that form in deep magma are called plutonic igneous

rocks.



Igneous rocks.

The most well-known igneous rocks include granite and basalt.

Igneous rocks are usually classified using composition and texture.

Plutonic types have mineral grains that can be seen by the human

eye. However, extrusive and intrusive usually cannot be observed

without a microscope.

Igneous rocks may be subject to weathering. The rock will be broken

down to sediments, which will eventually form a sedimentary rock.

If an igneous rock remains buried, it could undergo high

temperatures and pressure, which could transform it into a

metamorphic rock.



Sedimentary rocks.

Unlike igneous rocks, sedimentary rocks were created cool, instead

of hot. Most sedimentary rocks come from the earth¶s surface,

located underwater in the ocean. Sedimentary rocks were originally

rocks that were broken into smaller pieces by weathering. The

broken pieces of rock fall down streams and rivers, like runoff. Theythen begin to pile up and the sediments from the original rocks form

layers, which are pressed together over time. They begin to compact

together. The result is a sedimentary rock.

There are three types of sedimentary rocks, depending on what they

are made of.



Sedimentary rocks.

Clastic sedimentary rocks are the most common sedimentary rocks, as they

are made by mud, sand, gravel, and clay. Stones, shells, and other objects

may also be included in the sediment.

Organic sedimentary rocks form in the sea as shells built from plankton. The

shell is made from silica. Many shells pile up on the seafloor, and it

eventually gets thick in layers. The resulting material turns into limestone or

chert.

Chemical sedimentary rocks come from large areas in the sea that begin

drying up. The minerals eventually come out of solution, which results in

limestones, dolomites, gypsum rock, and salt rock.

Sedimentary rocks may change into metamorphic or igneous rocks withpressure and heating.



Metamorphic rocks.

Metamorphic rocks are created when either igneous or sedimentary rocks

change underground due to heat, pressure, fluids, and strain.

During contact metamorphism, hot magma forces itself into the rock.

During regional metamorphism, an area of rocks are faced with massive

pressure and extreme temperatures. This leads to significant physicalchanges for the rock.

High pressure and heat cause rocks to break down and change. Fluids are

held by rocks, and sedimentary rocks hold the most water. Fluids can

wander away, which changes the chemical composition of the rock that it

came from. Strain is when a rock¶s shape changes due to stress. When

combined with heat and pressure, strain can layer metamorphic minerals.When the strain increases, the foliation also increases. Foliation is the

presence of mineral layers. When the foliation increases, the minerals

thicken their layers. An increase in strain causes the rock to have greater

density.



Metamorphic rocks.

You can classify metamorphic rocks by texture and composition.

Foliated metamorphic rocks are formed when great pressure acts on a rock,

which causes the minerals to align in a similar fashion. Minerals may then

recrystallize, with a different orientation, which makes the rock look layered.

Non-foliated metamorphic rocks are rocks that do not have a layeredtexture. Usually, these type of metamorphic rocks only contain one mineral.



Weathering and Erosion.

Weathering is the process of breaking down rocks into sediments. There

are two types of weathering.

Mechanical weathering is when the rock is broken down into smaller

sediments without making any changes to the chemicals within. Examples

of mechanical weathering include temperature, freezing, and ice.

Chemical weathering is when the rock is broken down into sediments with

different chemical and mineral composition than the original rock. A general

example of this would be water seeping into a rock, which over time

changes the chemical makeup.

Erosion is the transportation of sediments. Erosion is related to deposition,

where the sediment is deposited to a different location. The agents of erosion are gravity, waves, water, wind, and glaciers.



Weathering and Erosion.

Weathering is similar to erosion because they are both

responsible for the continuous cycle of the reshaping of

Earth¶s surface. Weathering breaks down the sediments

so that erosion can deposit them to a new location.

Weathering is different than erosion because while

erosion only transports the sediments by wind, water,

glaciers, waves, and gravity, weathering is what breaks

the original rocks to sediments so they can be deposited.

These sediments may become a sedimentary rock over time, due to the pressure of the sediments piling on top

of each other, gradually creating layers.



References

Sonia Nair, No date listedHow does Coal become a Diamondhttp://www.buzzle.com/articles/how-does-coal-become-a-diamond.html

rocksandminerals4u( no specific writer listed ), No date listed.

Mineral propertieshttp://www.rocksandminerals4u.com/properties_of_minerals.html

Andrew Alden, No date listed.About Igneous Rockshttp://geology.about.com/cs/basics_roxmin/a/aa011804a.htm

No author listed, March, 2000Metamorphic Rockshttp://library.thinkquest.org/J002289/meta.html

Andrew Alden, No date listed

About metamorphic rockshttp://geology.about.com/cs/basics_roxmin/a/aa011804c.htm



References

Andrew Alden, no date listed

About sedimentary rocks

http://geology.about.com/cs/basics_roxmin/a/aa011804b.htm

Jennifer Horton, no date listed

How landslides work

http://science.howstuffworks.com/environmental/earth/geology/landslide2.htm

bedrock geology c.c - stanley ppt

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