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Beginners Guide to Geology

Updated on November 25, 2013

This guide is aimed at beginners in the study of geology which is the study of the origin, history and structure of the Earth, and for anyone interested in minerals and gemstones, like me, is a must to take up either as a hobby or a career. To understand how minerals are formed, it is necessary to have a basic grounding in geology, to be able to recognise the types of rocks and the crystals formed millions of years ago within.

In each different type of rock are different crystals, depending on the chemical elements contained within the rocks.

The Earth is entirely made up of elements and minerals which are mixtures of elements.

There are 90 known elements, as laid out on the Periodic Table of Elements that you may remember from science classes at school.

At the present time, there are 3,700 known minerals, with new discoveries each and every year as scientific equipment gets better.

Our world is made up of rocks, molten or otherwise. From where we stand on the surface of the earth, there is a massive 10 miles of solid bedrock below us. Contained within this are minerals.

These 10 miles (the distance is shallower in the depth of the oceans) are called the crust.

Below the crust is the mantle. The mantle is 1,800 miles deep. The deeper you go, the hotter the bedrock becomes.

Below the mantle is the 3,000 mile outer core which is made of molten rock, consisting of mostly iron and nickel.

At the inner core it is reckoned to be solid rock once again, with a depth of 900 miles. It is believed to be made up of mostly iron, with a little nickel thrown in.

There is 4000 miles between where you are standing and the centre of the Earth.

The planet is millions of years old. There are various scientific theories as to how the Earth formed, and no-one knows for certain. The Big Bang Theory sounds the most plausible.

However, it is generally accepted that the Earth formed 4½ billion years ago (4,600,000,000) and that at the time of forming it was super hot.

We know there have been several Ice Ages since then and all have shaped the Earth as we know it.

Volcanoes push molten lava out from the outer core through weaknesses in the Earth’s mantle causing mountain ranges to form, while glaciers change the shape of whole mountains.

Shifts in the tectonic plates of the world have also moved continents and land masses to where they are today. The existence of tectonic plates is a modern day theory to explain this phenomenon.

There are reckoned to be 8 large tectonic plates.

· Antartic

· African

· Arabian

· North American

· Nasca

· Eurasian

· Indian-Australian

· Pacific

· South American

And many various smaller ones

· Anatoliah

· Arabian

· Caribbean

· Cocos

· Philippines

· Somali

· Juan de Fuca

· And more

Scientific tests have proven that they are all moving, very slowly and at various rates. Over the millions of years the Earth has been in existence they may have re-organised themselves many times. The tectonic plates sit on the surface of the Earth’s mantle.

Where they move away from each other, molten rock, called magma, from the mantle may escape through, and this may form new mountain ranges, or new islands or land masses when it occurs at sea. This is where strong volcanic activity is present.

When they move towards each other, they cause earthquakes, which as we all know are devastating to life on the Earth’s surface.

On these giant tectonic plates lie many fissures and faults, which cause weaknesses within the plates. These are known as fault lines, along which earthquakes periodically occur.

Rocks are made up of three types

1. Sedimentary

2. Igneous

3. Metamorphic

Sedimentary rock is the youngest type of rock, and is the type that has been carried along on river beds, or swept down mountains by glacial activity. The effects of wind and water erosion swept this rock off the old bedrock or extrusive rock (rocks that we can see – mountains etc) and over a period of several million (or even 1000s) years, compaction of this gravel, or old vegetation and other waste matter turned to solid rock.

Igneous rock is the oldest type of rock on Earth. Formed as the name suggests, from fire, igneous rock is solidified molten magma, and is widespread throughout the planet, proof of our fiery-hot beginnings. 95% of the earth’s crust is made up of igneous rock.

Metamorphic rock is, as its name suggests, rock that has been changed. Heat and pressure deep under the Earth’s surface has mixed igneous rock with sedimentary rock and the result is metamorphic rock, within which are found many of the world’s minerals and crystals.


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    • profile image

      Ian Miller 

      21 months ago

      Hi IzzyM. Thank you for this reintroduction to geology. I see that you wrote this page some years ago, so if you read this, then thank you. If I succeed in my dream / ambition to become a geologist, then know you were the first step in my reading.

    • Harshit Pandey profile image

      Harshit Pandey 

      6 years ago from Varanasi

      Good brief introduction on Geology for a beginner. It provides all the key information that one needs to know. Keep them coming. :)

    • eec2011 profile image


      8 years ago from California, USA

      Pretty good start.

    • IzzyM profile imageAUTHOR


      10 years ago from UK

      Thankyou :)

      I meant to expand on this subject but just haven't got round to it yet....I am personally fascinated with geology and wish I'd worked harder at school and studied it at university. Too late now, but I can still be a keen amateur.

    • 2patricias profile image


      10 years ago from Sussex by the Sea

      Hi Izzy,

      We have just published a hub called "Cambridge Attractions The Sedgwick Museum of Earth Sciences" I am adding a link from our hub to this one, as this is such a good introduction to Geology.

    • IzzyM profile imageAUTHOR


      10 years ago from UK

      Thanks 2patricias :)

      If it's any help, grapes don't need fertile soil to grow on - they just need it to be well-draining, with some warmth and plenty of sunshine :) Well, that is the grapes here of course - there will be different needs for different varieties I suppose.

    • 2patricias profile image


      10 years ago from Sussex by the Sea

      Interesting idea for a Hub. I remember bits of this from school. More recently I have become interested in how the local soil influence crops, especially grapes (as in wine).

      Thanks for all the research on this hub, I am sure it will do well.

    • IzzyM profile imageAUTHOR


      10 years ago from UK

      Thanks Duchess. I've got another almost completed that is sort of interlinked but not straight science,if you know what I mean :)

    • profile image

      Duchess OBlunt 

      10 years ago

      your love for the topic certainly shines through IzzyM. Very well put together and informative.

    • IzzyM profile imageAUTHOR


      10 years ago from UK

      @humagaia, I am so jealous you got to study at uni. I tried to get into uni as an adult returner to study geology, but in the end didn't go because they did full summer field trips abroad as part of the course and I couldn't go as I had a family. Good idea on the group of hubs. We can write them individually and group them all together.

      @Merlin, yes I do understand the continental shift moved a lot of things around.

      Even in my own mountainous area here in the south of Spain the rocks are fascinating. Soft red sandstone with seashells in it, layer volcanic igneous outcrops and we are at least 400 metres above sea level. I keep telling people all this must have been under the sea at one point, but no-one seems interested.I need to learn more about it before I can write a hub about it, but it's all fascinating.

      A neighbour of mine found beautiful dark green cuboid crystals when digging land for house foundations. She moved away and took them with her! I want a name for them now! I want to find more.

    • Merlin Fraser profile image

      Merlin Fraser 

      10 years ago from Cotswold Hills

      Hi Izzy,

      What would you think if of you found those same polished pebbles on the distant foothills of the Himalaya’s, thousands of miles from any beach.

      Or to find sharks teeth on a dessert plateau in northern Peru 2,000 feet above sea level.

      Speaking of plate tectonics where the entire land mass of the world was one giant continent before it drifted into the familiar shapes of today.

      Those plates are still moving and one day in the future it will be one giant continent again.

    • humagaia profile image

      Charles Fox 

      10 years ago from United Kingdom

      Izzy hi again. I have a similar interest in geology, geomorphology, geochmistry, in fact all earth sciences. I studied Life Sciences at Uni but I was also offered a place to study geochemistry (volcanoes and all that stuff). Life Sciences won only because I wanted to do oceanography. Perhaps we can hook up on a group Hub experience by creating a number of Hubs around a subject you are interested in - crystallography. What do you reckon?

      By the way, let me know when next you hit the 100 mark. I have created a Hub to record the 'Hall of Fame' of those Hubbers that have reached a HubTon and become HubTonners.

    • IzzyM profile imageAUTHOR


      10 years ago from UK

      Come on! You weren't thinking about plate tectonics - you just wanted a jigsaw to do!! Numpty! lol No chance of kids doing that now - they probably don't have maps in school anymore! (Cut-backs)

      I'm fascinated by geology - especially rock formations and crystals and semi-precious stones - not that I can honestly recognise most of them. Most of the pebbles I ever saw were on the sea-shore where they were rounded by sea action and almost impossible to recognise without a geology degree! The internet is great for looking them up - all sorts of pictures and hints on how to determine what they are exactly.

    • Merlin Fraser profile image

      Merlin Fraser 

      10 years ago from Cotswold Hills

      Hi Izzy,

      Seems we have another interst in common, I became interested in Geology while working for an Oil company and of course all Oil companies have a Geology department and obviously they play a vital role in the discovery of Oil and Gas.

      However, back in the 1950's it seems I had my own theory of plate tectonics because I cut up a school Atlas to create a Jigsaw puzzle by removing the oceans.

      The only part that I couldn't make fit was India, I didn't realise at the time where that had come from.

      Needless to say I was branded as a complete idiot by the Geography teacher and subjected to 6 of the best for destroying school property.

      Do you think I could still Sue them ?

    • IzzyM profile imageAUTHOR


      10 years ago from UK

      Aw thanks Jule :)

      It's just something I wanted to write about. I love geology.

    • Jule Romans profile image

      Jule Romans 

      10 years ago from United States

      What a great idea for an article. Packed with great information. I hope this one reaches the top. It is great.


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