4. Rock types and the rock cycle 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
Go to the Geography website where you’ll find a link to an animated version of this picture.
Rock Type Igneous o Intrusive e.g.
How it’s formed
o Extrusive e.g.
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department
Rock Type Sedimentary e.g. o Sandstone
How it’s formed
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. 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. 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.
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
GCSE Theme C: The Dynamic Earth – Lurgan College Geography Department