In this activity you will be introduced to the facinating topic of Geology! You can do the activities on this page using resources that you have at home or in the class room, or in conjunction with one of our rocks loan boxes. We also offer sessions on this topic at the Museum or as outreach.
What is Geology
Geology is the study of the solid parts of the Earth and what it is made of; the scientists who study it are called geologists. Geologists dont just study rocks (the study of rocks is called petrology), they also study natural hazards like landslides, volcanoes, earthquakes, and floods. Geologists study some of the worlds most important issues such as water, energy, mineral resources and climate change.
A expreinced geologist can look at the landcape and read its history - isn't that amazing!
We are going to begin our journey into the geology with some petrology, so that means studing rocks! Lets start with the basics and begin by finding out - what actually are rocks?
What is a rock?
Rocks are a solid mass at room tempreture. They are made when mineral grains grow or are fused together. Every rock is made up of one or more minerals.
A mineral is a naturally occurring inorganic solid, with a chemical composition that is defined, and an ordered atomic arrangement.
This may all seem a bit complicated so lets break down the sentace a little:
A mineral is naturally occuring: This means it is not made by humans
It is inorganic: This means is is not alive and never has been
It is a solid: it is not a gas (like oxygen) or liquid (like water)
It has a defined chemical compostition: This means it is made up of an exact mix of chemical
It has an ordered atomic arrangement: This means it atoms (small chemical building blocks) are oarranged in a particular way. This is why minerals form or "grow" as crystals.
Rocks are made of different minerals that have been combined togther by diffrent processes. Rocks are catogrised by the proceses that formed them. Lets look at those next.
How are rocks made?
There are three main groups of rocks: sedimentary, igneous, and metamorphic. Each of these groups of rocks are formed by different phisical processes like melting, compacting, eroding and cooling. These process are the rock cycle, which you can explore below.
Magma from the multen crust and mantle
What are the different types of rock?
As you can see there are three groups of rocks, igneous, metomorphic and sedimentary. Click on the pictures below to find out about their properties.
These rocks are formed from from fragments of other rocks that become joined together.
A river carries pieces of broken rock as it flows. When the river reaches a lake or the sea the rocks that it is carrying settles to the bottom. This is called being deposited. The deposited rocks build up in layers, called sediments. This process is called sedimentation. As these sediments get buried by other sediments they are exposed to heat and presure which squashes the pieces of rock togther to form sedmintary rocks
Metamorphic rocks begin as other rock, these rocks are subjected to high heat, high pressure, hot mineral-rich fluids or a combination of these factors. These factors substantially change metomorphic rocks from their original sedimentary, ignious, or metamorphic form. The conditions that form metomorphic rocks are found deep within the Earth or where tectonic plates meet.
Igneous rocks are created from molten rock that has cooled and solidified. The speed at which it cools changes the apearence of the rock.
Magma comes from the centre of the earth, where it is so hot that rocks melt. Somtimes the magma breaks through the earths crust and erupts from a volcanoe.
You have been introduced to a lot of new vocabulary in the first part of this session, see if you can match the words to the deffinitions in the games below. Don't worry if you don't get them all, just read back over the information above and try again! When you play the game, make sure it is on full screen or it may be to small to see.
Geology in action: Uttlesford
It can be hard to see geology in Essex - we don’t have many cliffs or clearly visable landscape features like mountains. This doesnt mean that you cant study the geology in your back garden or local area, you just need to look for somthing a little smaller.
It’s easy to find pebbles in gardens and fields, and see them in the walls of old buildings. Each pebble tells a story, and literally millions of years of history can be revealed by the shape, texture and composition of a pebble.
Uttlesford has a greater range of pebble types than anywhere else in Essex.
This is because most of our countryside is blanketed by a great thickness of boulder clay that was left behind by the melting of an ice sheet during the Ice Age. During the coldest glaciations the ice sheets spread out from Scandinavia and Scotland to cover much of the UK.
It was during the coldest of these periods, some 450,000 years ago and known as the Anglian Glaciation, that the ice sheet, hundreds of metres thick, covered the whole of Uttlesford and reached as far south as north London. This ice sheet diverted the Thames from its much more northerly course across East Anglia to roughly the course it follows today. It also deposited the boulder clay which, in places, is nearly 50 metres thick.
This clay once covered the whole of the district but modern rivers have removed it in the valleys so it can now only be found on the higher ground. The ice sheet spreading from Scandinavia and Scoltland means that we can find some more exotic pebbles.
In the gardens and on the footpaths here you will often encounter an unusual pebble – perhaps a piece of limestone full of fossils from Lincolnshire, or a lump of gritstone from Derbyshire, or a dark-coloured dolerite from Northumberland, or maybe a colourful granite from Scotland? But the most common pebbles by far will be of chalk and flint – the bedrock of much of this area.
Activity: Geology bingo!
Its now time for you to become a Geologist! You could do this activity in your back garden if you have one, in the playground with your class or out on a walk.
Look at the sheet below on the different types of pebble you can find in Uttlesford. Take a copy out on a walk with you (you are free to print and dowload it for personal use) and see if you can find an example of each. As you see them, cross them off and once you have them all its BINGO!
We hope you have enjoyed this introduction to the rock cycle and Geology!
Special thanks to Gerald Lucy for providing us with some of the text and the super sheet to use for geology bingo with photos and text adapted from the full colour poster ‘Pebbles in Essex and Beyond’ © Essex Rock and Mineral Society. The poster charts the formation of many of our pebble types from their origin in Cornwall, Wales or elsewhere to their current resting places on our beaches and
in our gardens. Along the way it tells the story of the origins of the landscape we see today. Available from the society’s website:
http://www.erms.org/pebbles-poster.html or from Saffron Walden Museum shop (Price £2).