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The Rock Cycle

 

volcano The Rock Cycle

 

This image is a diagram illustrating the rock cycle. It shows various stages of the cycle, including the formation and transformation of different types of rocks due to natural processes like volcanic eruptions. The diagram is labeled “ROCK CYCLE,” and has an icon of a volcano erupting at the top. The cycle starts from magma, which cools down to form igneous rock. Igneous rock breaks down into sediment, which compresses into sedimentary rock. Sedimentary rock under heat and pressure transforms into metamorphic rock, which melts during volcanic eruptions, turning back into magma. The diagram uses arrows to indicate the flow of the cycle from one type of rock or material to another.

The rock cycle

 

There are 3 types of rocks. They are:

 

These rocks are recycled over millions of years.  They change from one to another in a slow cycle.  This is shown in the Rock Cycle below:

Igneous Rocks.

 

Igneous rocks ("igneous" as in ignite - from fire) are made when molten magma pushes up into the crust or right onto the earth's surface.  It contains many different minerals in randomly arranged interlocking crystals.  There are 2 types of igneous rocks:

 

Extrusive - molten rock comes straight out of the mouth of a volcano ("Ex-" as in "Exit").  This type of rock has small crystals due to quick cooling on the Earth's crust and beneath water. BASALT is the main example.  Most ocean floors are made from basalt.

 

Intrusive - molten rock that never reaches the surface.  This type of rock has big crystals due very slow cooling beneath the surface, like GRANITE.

 

 

Metamorphic Rocks.

 

Igneous and sedimentary rocks can be changed by high temperature or high pressure into much harder rocks, called Metamorphic rocks (from the Greek for 'change of shape').

 

This happens when movement of Earth's crust can bury rocks deep underground.  As one goes deeper into the Earth's crust, the temperature and pressure gets higher and under these conditions, rocks have their mineral structure and texture changed, without actually melting.  

 

The minerals in rocks arrange themselves into lines, resulting in band or sheets, to form metamorphic rock. 

 

Rocks can also be 'baked' nearer the surface by molten rock known as magma.  Magma rises towards the surface through faults in the Earth's crust.  This happen quite often under volcanoes, the rocks near the magma get very hot.  The temperatures are very high enough to change their structure.

 

Some examples Metamorphic Rocks.

 

Slate: It is formed when mudstone or clay gets moderately heated and compressed a lot.  Its tiny plate-like particles align in the same direction.

For this reason, the resulting slate can easily be split along that direction into thin sheets which make ideal roofing material.

 

Marble: It is made when limestone is subjected to high temperature and pressure.  Limestone reforms as small crystals.  This results in marble having a more even texture and makes it much harder.  Marble can be polished and is used as decorative stone as it has attractive patterns.

 

Schist:  When mudstone is subjected to a very high temperature and pressure, new minerals like mica begins to form and produce layers.   This creates a rock containing bands of interlocking crystals known as Schist.  These bands of crystals are typical of a metamorphic rock.

 

 

 

Sedimentary Rocks

 

Sedimentary rocks form when other rocks slowly weather away.  They are then carried off to another place.  Eventually, they settle as sediment.   As time passes, layers of sediment pile up.  

 

 

The pressure on the older, lower layers builds up.  Any water in between the particles of sediment is squeezed out.

 

The water often has minerals dissolved in it.  These minerals are left behind in the sediments, and act like cement, binding the sediments together to the sedimentary rock.

 

 

    Only Sedimentary rocks contain Fossils.

     

    Fossils are only found in sedimentary rocks.

  • Fossils are not found in the other two types of rock (igneous and metamorphic) because they have been through too much heat and turmoil.

  • Fossils help us to identify rocks of the same age, because fossilised remains that are found change, due to evolution, as the time periods pass.  This means that if 2 rocks have the same Fossilsthey must be from the same age.

 

 

There are four main Sedimentary rocks.

 

These rocks tend to look similar to the original sediments from which they are produced.  This is not surprising as very little has happened to them other than that they have been squashed together.


  • Sandstone

     

    • This is made from sand obviously.  It looks like it as well, since all the sand particles are stuck very strongly together.  There is yellow sandstone and red sandstone and these are commonly used to make buildings.

     

     

  • Limestone

    • This is made from seashells.  It is predominantly calcium carbonate and is grey/white in colour.  The original shells are mostly crushed but there are still many fossilised shells to found in limestone.

     

     

  • Mudstone or shale

     

    • This stone was made from mud which really means much finer particles than sand.  It is dark grey in colour and tends to split into the original layers very easily.

     

     

  • Conglomerates

     

    • This can be comparedwith man made concrete, containing pebbles set into cement of very fine particles.

     

     

    A hyper-realistic 3D isometric cross-section of a landscape, styled as a professional CGI render (Blender/3DS Max) on a clean, dark gray studio background. The model illustrates the stages of sedimentary rock formation. The Landscape: At the top of the "block," a detailed mountain range features jagged, realistic rock textures and light mist. A river flows from the mountains down to a small bay of translucent blue water. Green coniferous trees and sandy beaches line the coast. An arrow at the top right points from the mountains toward the water, labeled "EROSION: particles carried away by wind or water." The Underground Strata: The side of the block reveals multiple geological layers (strata) in varying shades of brown, gray, and tan, showing realistic textures of compressed sand, silt, and pebbles. The Process Circular Callouts: To the left, three glass-like circular magnifying bubbles are connected to specific layers by thin lines: Deposition: The top bubble shows large, loosely arranged river stones and pebbles submerged in water, labeled "loosely packed sediments." Compaction: The middle bubble shows smaller pebbles pressed closely together with minimal space between them, labeled "closely packed sediments." Cementation: The bottom bubble shows pebbles fused together by a solid, sandy matrix, labeled "tightly packed sediments." The title "FORMATION OF SEDIMENTARY ROCKS" is displayed in bold, 3D metallic-style lettering at the top of the frame.Formation of Sedimentary Rocks

     

    💎 Knowledge Check: The Rock Cycle

    Test your knowledge on the three main types of rocks and how they are linked through geological processes.

    1. What process causes rocks to break into smaller pieces known as sediment?

    2. Which type of rock forms directly from the cooling of magma or lava?

    3. Metamorphic rocks are created when existing rocks are changed by which two factors?

    4. In which type of rock are you most likely to find fossils?

    5. What happens to rock when it is pulled deep underground and becomes extremely hot?

    Click to Reveal Answers
    1. Weathering and Erosion (The breaking down and movement of rock pieces).
    2. Igneous (Formed from cooled molten rock).
    3. Heat and Pressure (Conditions that change rock without melting it).
    4. Sedimentary (Formed in layers where organic remains can be trapped).
    5. It melts into magma (Extreme heat deep in the Earth turns solid rock back into liquid).

     

    Tags:Rock cycle, Igneous, Metamorphic, Sedimentary, Rock cycle ks3

     

     

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