The Rock Cycle

NASA video

The three types of rocks– Igneous– sedimentary– Metamorphic

All types of rock are subject to processes that change one rock type into another.

Igneous RocksFormed from cooled and solidified magma– Intrustive• formed from the cooling of magma within the earth’s

crust• Cools and hardens slowly • Coarse grained- forms large, well-developed crystals

– Extrusive• melted rock that hardens on the earth’s surface• Lava cools rapidly• fine grained rocks

Composition of Igneous Rocks• Felsic- Rocks in the granite family – Light colored– High silica content– Low magnesium and iron content

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• Mafic- Rocks in the basalt family – dark colored– lower silica content– high mg and fe content

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• Andesitic - Medium Silica– Green, grey, or brown

Sedimentary Rocks• rock formed from the debris of both other rocks and

living matter.• 90% of the earth’s crust is made from igneous rock,

but 75% of the world’s land surface is covered with thin layers of debris or sediments.

• These sediments settle on the beds of oceans, lakes, and rivers, and recompacted over millions of years to form sedimentary rock.

How are Sedimentary Rocks Formed?• DIAGENESIS-

– the process that turns loose sediments into rock – COMPACTION- • the slow squeezing of sediment to form hard rock

– CEMENTATION- • The binding together of compacted sediments by

chemicals like calcite, silica, and iron

3 types of Sedimentary Rock:– CLASTIC- form from rock fragments weathered

and eroded by glaciers, wind, rivers, and waves.– ORGANIC- rock made from the remains of plants

and animals– CHEMICAL- rock made from chemicals dissolved in

water

BEDDING PLANE- a boundary between one layer of sedimentary rock and another

Metamorphic Rocks• formed from other rocks as a result of intense

heat, pressure, and chemical processes– most form deep beneath the surface of the earth– formed from existing igneous, sedimentary, or

metamorphic rock

Types of metamorphic formation:• Contact metamorphism: – when hot magma pushes through

existing rock, changing the structure and composition of the rock. Only rocks near the magma are changed.

• Regional metamorphism: – movement of one tectonic plate

against another causes heat and pressure, affecting rocks over an area of many thousands of kilometers

Types of metamorphic rocks:• Foliated: – show visible parallel bands of minerals ex: slate,

schist• Unfoliated: – no bands of crystals ex: quartzite, marble

• animation

Interactive animation