Rocks

Hafeet mountain

There are several steps that lead to form the rocks

• Weathering • Erosion • Deposition • Heat and pressure

Weathering

• Ice (expand inside the rock fractures)• Plants (grows through fractures )• Changing temperature • Sea waves All of these factors lead to form sediments

(small rock fragments)

Erosion

• Since we got the sediments now its time to transfer them to a new place by a process called erosion

• Factors control on erosion : 1- water 2- wind

Deposition

• Its a process that lead to laying down the eroded sediments

• The major factor that control on this process is GRAVITY

Heat and pressure

• All the sediments which they laid down they will expose a lot of heat and pressure in order to form the final rock after that the new rock will go in a process called ROCK CYCLE

Rock cycle

Rock cycle : its a continues process that led to form different types of rocks .

Types of rocks : 1- sedimentary. 2- igneous. 3- metamorphic. The rocks has been classified according to their

own texture and composition.

Igneous rock

Jees mountain -UAE

First we have to know how lava formed

• 1- changing the composition of other rock. • 2- applying pressure • 3- finally the temperature

But how all of these factors works in order to form the lava? . (Check up the next slide )

Now lets talk about the igneous rock classification

Igneous rock classification

Classified by composition

Felsic

Granite

Mafic

Gabro

classified by the size of grains

Intrusive (coarse grains )

Granite & Gabro

Extrusive (fine grains )

Rhyolite & Basalt

Igneous bodies

• When magma intrudes, or pushes, into surrounding rock below the Earth’s surface and cools, the rock that forms is called intrusive igneous rock.Intrusive igneous rock usually has a coarse-grained texture because it is well insulated by surrounding rock and cools very slowly. The minerals that form are large, visible crystals.

• Plutons: are large, irregular-shaped intrusive bodies.• batholiths :The largest of all igneous intrusions.• Stocks: are intrusive bodies that are exposed over smaller

areas than batholiths.• Dikes: Sheetlike intrusions that cut across previous rock

units • Sills : are sheetlike intrusions that are oriented parallel to

previous rock units.

Where can l fine an extrusive igneous rock ?

1. From volcanoes 2. From mid ocean ridges

Sedimentary rocks

How sedimentary rocks formed?

• Sedimentary rock forms at or near the Earth’s surface. It forms without the heat and pressure that are involved in the formation of igneous and metamorphic rocks.

Follow the below chart that lead to form the sedimentary rocks

Compaction and cementation All the sediments start to compact to each other , after that some minerals work as glue that hold all the particles of the rock

together by cementation process (quartz or calsite )

Deposition

Laying down of the sediments

Erosion

Transferring the sediments.

Weathering

A process in which sediments formed.

• The most noticeable feature of sedimentary rock is its layers, or strata. A single, horizontal layer of rock is sometimes visible for many miles.

Older

Younger

Sedimentary rock

classification

Clastic(according to

the size of grains )

Fine (shale) Medium(silt &sand stone)

Coarse (conglomerat

e)

Non- clastic

Chemical(halite)

Organic(fossiliferous lime

stone )

Clastic sedimentary rocks

• Is made of fragments of rocks cemented together by a mineral such as calcite or quartz

• Cementation : is a process in which a clasticrock stick together

• They have coarse-grained, medium-grained, or fine-grained textures.

Chemical sedimentary rock

• Chemical sedimentary rock forms from solutions of dissolved minerals and water.

• Halite, one type of chemical sedimentary rock• Halite forms when sodium ions and chlorine

ions in shallow bodies of water become so concentrated that halite crystallizes from solution.

Halite

Organic sedimentary rock

• This type of rocks form from animals remains .• Most limestone forms from the remains,

or fossils, of animals that once lived in the ocean

• These animal remains eventually become cemented together to form fossiliferouslimestone.

Example of organic sedimentary rock

Sedimentary Rock Structures

• Stratification : is the process in which sedimentary rocks are arranged in layers.

• Ripple marks : recording the motion of wind ,water waves and sand dunes in a sedimentary rock .

• Mud cracks: form when fine-grained sediments exposed to the air and dry out

Ripple marks

Mud cracks

Metamorphic rocks

The meaning of metamorphic rocks

• They are rocks their own composition and texture has been changed because of intense heat and pressure.

What are types of metamorphisim?

Metamorphism

Contact

Controlled by heat

Happen because immediatlly magma intrusion

Regional

Controlled by pressure

Happen at the plate boundaries espicially in the convergent boundaries

Contact metamorphism The greatest change takes place where magma comes into direct contact with the surrounding rock. The effect of heat on rock gradually decreases as the rock’s distance from the magma increases and as temperature decreases. Contact metamorphism occurs near igneous intrusions

Regional metamorphism

• When pressure builds up in rock that is buried deep below other rock formations or when large pieces of the Earth’s crust collide with each other, regional metamorphism occurs. The increased pressure and temperature causes rock to become deformed and chemically changed.

The composition of metamorphic rocks

• Metamorphism occurs when temperature and pressure inside the Earth’s crust change. Minerals that were present in the rock when it formed may not be stable in the new temperature and pressure conditions.Index minerals can indicate the amount of heat , pressure and

depth

What is Garnet Its one of the index minerals which shows the highest amount of metamorphism.

Classification of metamorphic rocks.

Metamorphic rocks

Foliated

The texture of metamorphic rock in which the mineral grains are arranged in

planes or bands

Non-foliated

The texture of metamorphic rock in which the mineral grains are not

arranged in planes or bands

Example of foliated metamorphic rocks

Foliated metamorphic rock usually contains aligned grains of flat minerals, such as biotite mica or chlorite

Example of non-foliated rocks

• Done by Mr,AliScience teacher