Evidence for Rock Formation and Deformation

Evidence for Rock Formation and Deformation

Different Types of Rock

Many different processes have produced the characteristics of the Earth's surface. These same processes ensure that the surface of the Earth is constantly changing!

Rock formation by heat - igneous rocks:

Deep inside the Earth is molten (liquid) rock. At times, this molten rock (magma) finds weaknesses in the Earth's crust and is thrown outside.

These 'gaps' in the crust are called volcanoes - they throw dust, fragments of rock and magma from a hole at the top. These fiery eruptions eventually solidify to form igneous rock. Around the volcano, new land develops as layer upon layer of rock form.

Examples of igneous rock are granite and basalt.

Evidence for Rock Formation and Deformation

Igneous rocks tend to be hard with many containing interlocking crystals.

Rock formation from sediments:

These are called sedimentary rocks.


Wind, rain, snow, sea, rivers, oceans and glaciers can cause land to be worn away.

This process of wearing away is called 'erosion'.

Rocks that have been weathered and eroded into small fragments are often found in rivers or in the sea being transported. Eventually, these fragments settle at the bottom of river or sea beds.

In time, this sediment will eventually harden and become new layers of rock. These sedimentary rocks are made from recycled material from older rocks.

Dead animals and plants are often trapped in the layers of sedimentary rock - they can form fossils over many years.

Evidence for Rock Formation and Deformation

Examples of sedimentary rock are limestone, chalk and sandstone. Sedimentary rock tends to be crumbly, often contain a layered effect and may contain fossils.

Evidence for Rock Formation and Deformation

Rock formation from rocks that change with heat and pressure:

In many places on Earth, layers of sedimentary rock have been squashed, buckled or broken. Inside the Earth great forces act to cause these effects.

Mountains are made from rocks that have buckled up and heated while deep under other rock. These new rocks which have formed from sedimentary rock been subjected to heat and/or pressure is called metamorphic rock.

Examples of metamorphic rock are marble and slate. Metamorphic rock is very hard.

Evidence for Rock Formation and Deformation