how sedimentary rock is formed

7/28/2019 How Sedimentary Rock is Formed

1/25

GEOLOGY AND CIVIL ENGINEERING

CEG 04


2/25

I I Engineers, Geologists, & Society

A Engineers

1. Solve problems

2. Quantitative analysis emphasized

3. Models often simplified/simplistic

B Geologists

1. Study problems

2. Qualitative analysis emphasized (traditionally)

3. See earth as complex (heterogeneous & anisotropic)

C Society

1. Pays the bills for problems and regulates response

2. Confused by conflicting analyses

3. Sees geologists and engineers as mysterious


3/25

The Geological Environment

Earth is an active planet in a constant state of change

Geological processes continually modify the earths

surface, destroy old rocks, create new rocks and adds to

the complexity of ground condition

Cycle of geology encompasses all the major processes

which must be cyclic, or they would grind to an inevitable

halt

Earth movemens are vital to the cycle, its hot interior of

the earth is the ultimate energy source which drives all

geological processes


4/25

Cycle of Geology

Sea

Mainly deposition,

Forming new sediments

Underground

New rocks are

created

and deformed

Land

Mainly erosion

and weathering


5/25

weathering

Land

Earth Movements

Igneous Rocks

Magma

Melting

Metamophic Rock

Metamophism

sedimentary Rocks

Liquefaction

Deposition

ErosionTransport

Sea

Air


6/25

Discover How Rocks Are Formed

Sedimentary Rock, Metamorphic Rock

And Igneous Rock
http://www.fi.edu/fellows/fellow1/oct98/create/sediment.htmhttp://www.fi.edu/fellows/fellow1/oct98/create/metamorph.htmhttp://www.fi.edu/fellows/fellow1/oct98/create/igneous.htmhttp://www.fi.edu/fellows/fellow1/oct98/create/igneous.htmhttp://www.fi.edu/fellows/fellow1/oct98/create/igneous.htmhttp://www.fi.edu/fellows/fellow1/oct98/create/igneous.htmhttp://www.fi.edu/fellows/fellow1/oct98/create/metamorph.htmhttp://www.fi.edu/fellows/fellow1/oct98/create/sediment.htm


7/25

For examples of sedimentary rocks, take a look at these:

How Sedimentary Rock Is Formed

For thousands, even millions of years,little pieces of our earth have been

eroded--broken down and worn awayby wind and water.

These little bits of our earth are washeddownstream where they settle to thebottom of the rivers, lakes, and oceans.

Layer after layer of eroded earth isdeposited on top of each.

These layers are pressed down more andmore through time, until the bottomlayers slowly turn into rock.


8/25

Sediment Transport

Gravity

Wind

Volcanoes Ice


9/25

Sediment Deposition

Water

Sea

Slopes Volcanoes

ice


10/25

Sedimentary materials

Sandstones Mineral grains

Physically and chemically stable minerals e.g quartz,

muscovite

Rock fragments and volcanic debris Clays

Breakdown products (clay minerals) and organic debris (plant

material to form peat and coal)

Limestones (solutes debris) Calcite precipitated from sea water due to biological activity

Gypsum and salt and other less soluble organic compounds


11/25

Lithification

Definition This is a process by which a weak loose sediment is turned

into a stronger sedimentary rock.

Lithification process

Is induced by burial pressure and slightly increasedtemperature beneath overlaying sediments

Lithification Processes Cementation

Re-crystallization

Compaction Consolidation Normally consolidated

over - consolidated


12/25

Sedimentary Rock Classification

Sedimentary Rocks

Clastic Rocks Non Clastic Rocks

Rudaceous

Coarse grained rocks

Arenaceous

medium grained rocks

Argillaceous

Fine grainedCarbonates Non-Carbonates

calcite

limestones

Allied rocks

ironstone

chert

coal

Salt and gypsum

conglomerate

Breccia

sandstone

Allied rocks

siltstone

Clay

Allied Rocks


13/25


Sandstone Sandstone rocks are

sedimentary rocks

made from small

grains of the mineralsquartz and feldspar.

They often form in

layers as seen in this

picture. They areoften used as building

stones.
http://www.fi.edu/fellows/fellow1/oct98/expert/sandstone.htmhttp://www.fi.edu/fellows/fellow1/oct98/expert/sandstone.htm


14/25


Limestone Limestone rocks are

sedimentary rocks that

are made from the

mineral calcite which

came from the beds ofevaporated seas and

lakes and from sea

animal shells. This rock is

used in concrete and isan excellent building

stone for humid regions.


15/25


Shale Shale rock is a type of

sedimentary rock

formed from clay that

is compacted togetherby pressure. They are

used to make bricks

and other material

that is fired in a kiln.
http://www.fi.edu/fellows/fellow1/oct98/expert/shale.htmhttp://www.fi.edu/fellows/fellow1/oct98/expert/shale.htm


16/25


Conglomerate Conglomerate rocks are

sedimentary rocks. They

are made up of large

sediments like sand and

pebbles. The sediment isso large that pressure

alone cannot hold the

rock together; it is also

cemented together withdissolved minerals.
http://www.fi.edu/fellows/fellow1/oct98/expert/conglomerate.htmhttp://www.fi.edu/fellows/fellow1/oct98/expert/conglomerate.htm


17/25


gypsum Gypsum rocks are

sedimentary rocks made

up of sulfate mineral and

formed as the result of

evaporating sea water inmassive prehistoric

basins. It is very soft and

is used to make Plaster of

Paris, casts, molds, andwallboards.
http://www.fi.edu/fellows/fellow1/oct98/expert/gypsum.htmhttp://www.fi.edu/fellows/fellow1/oct98/expert/gypsum.htm


18/25

For examples of metamorphic rocks, take a look at

these:

How Metamorphic Rock Is Formed

Metamorphic rocks are rocks that have"morphed" into another kind of rock.

These rocks were once igneous orsedimentary rocks.

How do sedimentary and igneous rockschange?

The rocks are under tons and tons ofpressure, which fosters heat build up,and this causes them to change.

If you exam metamorphic rock samplesclosely, you'll discover how flattened

some of the grains in the rock are.


19/25


schist Schist rocks are

metamorphic. These

rocks can be formed from

basalt, an igneous rock;

shale, a sedimentaryrock; or slate, a

metamorphic rock.

Through tremendous heat

and pressure, these rockswere transformed into this

new kind of rock.
http://www.fi.edu/fellows/fellow1/oct98/expert/schist.htmhttp://www.fi.edu/fellows/fellow1/oct98/expert/schist.htm


20/25


Gneiss Gneiss rocks are metamorphic. Theserocks 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


21/25

For examples of igneous rocks, take a look at these:

How Igneous Rock Is Formed

Igneous rocks are called fire rocks and are formedeither underground or above ground.

Underground, they are formed when the meltedrock, called magma, deep within the earthbecomes trapped in small pockets.

As these pockets of magma cool slowlyunderground, the magma becomes igneous rocks.

Igneous rocks are also formed when volcanoeserupt, causing the magma to rise above the earth'ssurface.

When magma appears above the earth, it is calledlava. Igneous rocks are formed as the lava coolsabove ground.


22/25


Granite Granite rocks are igneous

rocks which were formed

by slowly cooling pockets

of magma that were

trapped beneath theearth's surface. Granite is

used for long lasting

monuments and for trim

and decoration onbuildings.


23/25


Scoria Scoria rocks are igneous rockswhich were formed whenlava cooled quickly aboveground.

You can see where littlepockets of air had been.Scoria is actually a kind ofglass and not a mixture ofminerals.


24/25


Pumice Pumice rocks are igneous rockswhich were formed when lavacooled quickly above ground.

You can see where little pocketsof air had been. This rock is solight, 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, itis used quite often as adecorative landscape stone.

Ground to a powder, it is used asan abrasive in polishcompounds and in Lavasoap.


25/25


Obsidian Obsidian rocks areigneous rocks that formwhen lava cools quicklyabove ground.

Obsidian is actually glassand not a mixture ofminerals. The edges ofthis rock are very sharp.

how sedimentary rock is formed

Documents