2g. Rock Groups

What are the 3 main kinds of rocks

• igneous

• sedimentary

• metamorphic

How are sedimentary rocks formed?

Sedimentary rocks form from eroded rock and the remains of plants and animals. These materials are carried by rivers and deposited in the sea, where they settle in layers at the bottom. Over time, the layers are compressed and cemented together to form solid, stratified rock.

• Sedimentary rocks often contain fossils and fossil fuels (oil, coal, gas)

What kind are all of Malta’s rocks

Sedimentary

Give 3 examples of sedimentary rock

• limestone

• chalk

• shale

How does igneous rock form

• Igneous rocks form from magma or lava.

• When magma cools and solidifies beneath the Earth's surface, it forms intrusive igneous rock.

• When a volcano erupts, magma reaches the surface and is called lava. If the lava cools and solidifies on the Earth's surface, it forms extrusive igneous rock

What appearance are igneous rocks usually

crystalline

Give 3 examples of igneous rock; state if they are intrusive or extrusive

• Granite (intrusive)

• Obsidian (extrusive)

• Basalt (Extrusive)

How do metamorphic rocks form

• Metamorphic rocks form when existing igneous or sedimentary rocks are subjected to intense heat and/or pressure.

• These conditions cause the rocks to change their structure and properties without melting, forming metamorphic rocks.

What is a property of metamorphic rocks

• resistant to weathering and erosion (therefore are very hard-wearing)

Give 3 examples of metamorphic rock & state from what they are formed

• Slate (formed from sedimentary shale)

• Marble (formed from sedimentary limestone)

• Gneiss (formed from igneous granite)

What is the rock cycle

a never-ending process that describes how rocks can change from one type to another over time

Explain the rock cycle

• Igneous rock + weathering & erosion → become smaller pieces of rock (sediments)

• Sediments + deposition, compaction, cementation → sedimentary rock

• Sedimentary rock + heat & pressure → metamorphic rock

• Metamorphic rock + melting → magma

• Magma + cooling → igneous rock