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