GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department

4. Rock types and the rock cycle

Go to the Geography website where you’ll find a link to an animated version of this picture.

Rock Type How it’s formed

Igneous

o Intrusive

e.g.

o Extrusive

e.g.

Learning Outcomes – by the end of this section, you should be able to • understand the formation of the basic rock types and recognise their characteristics:

– igneous: basalt and granite; – sedimentary: limestone and sandstone;

– metamorphic: slate and marble. Key Terms

GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department

Rock Type How it’s formed

Sedimentary

e.g.

o Sandstone

o limestone

This sedimentary

rock made from

different elements

than sandstone.

How is it

different?

Metamorphic

• During subduction

• By heat from intruding magma

• Due to tectonic forces

GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department

Problem Solving - get it all in order

Use the following principles to work out the

sequence of events in this picture of an actual

exposed cliff face.

Use these principles to fill in the table below

to show the sequence of rock forming events

in the picture. Put the first event at the

bottom, finishing with the last event at the top

(this is the normal way of writing a series of

geological events – the past goes at the

bottom). The first has been done to help you.

Key sequencing principles are:

• The rocks on top are normally younger

• Anything which cuts through anything

else is younger.

• Rocks can only be changed (folded,

faulted or metamorphosed) after they have first been formed.

GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department

Problem solving: what lies beneath? Many of you will have been out on day trips to Portrush. You will have gone

on the dodgems at Barry’s. You will have played on the beach at East

Strand. You may even have clambered over the rocks of Ramore Head. But

while you imagined yourself as an intrepid mountaineer, you would have

been totally unaware of the argument that raged about just how the rocks

beneath you were formed.

Believe it or not, this question was at the centre of a massive controversy in the early days of the

science of geology. At that time, geologists weren’t sure about how exactly rocks were formed, but

there were two main theories, both seemingly supported by the evidence in the rocks at Portrush.

Here’s what they saw:

Vulcanists

.

Neptunists

GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department