Learning Sources

Here is a video that is catchy and actually helped me a lot with learning the difficult words such as "stratification"and "compaction", it's also quite entertaining, I hope you enjoy.

I highly recommend this website and so would most teachers as this section is based completely on the Irish junior certificate curriculum.

Metamorphic Rock

Metamorphic rocks are preexisting igneous and sedimentary rocks that have been changed due to heat and pressure. This can occur due to igneous activity where the original rock (prolith) is deep underground where it is subject to high temperatures an high levels of pressure, or it can occur due to tectonic activity where friction and pressure is created in converging plates also metamorphosing the rock. Some examples of metamorphic rock are marble (from limestone and quartzite (from sandstone). Marble can range from many different colours but the marble found in Connemara is known for its unique shade of green. Quartzite can be found in Donegal but also interestingly on the peak of The Great Sugarloaf Co. Wicklow.
<br> </br>

Here is a photo of the unique marble found in Connemara.

Sedimentary Rock

This type of rock is significantly different to that of igneous rock. This is because sedimentary rock is made out of other rock materials or the sediments of plantlife and marine organisms compressed. Sedimentary rock is formed through pressure underwater causing the sediments to turn solid. They are laid out into various layers called strata. There are three types; organic, inorganic and chemically derived. An example of an organic sedimentary rock is limestone. It is mostly made out of the fossils of organisms compressed. Another example is peat. An example of an inorganic sedimentary rock is sandstone and is made out of compressed rock materials and does not contain any organisms. An example of a chemically derived rock is gypsum and can be found in Cavan, but the most valueable example would be oil and gas such as that found off the coasts of Ireland.

Limestone is commonly found in the central plains of Ireland. Limestone rock would be used for construction as it is a very hard rock. The most noted limestone landscape in Ireland is in The Burren Co. Clare. This is due to the interesting features created by the erosion of the limestone by rain. This is called a Karst landscape and occurs when carbon dioxide in the rain creates a weak carbonic acid which erodes at calcium carbonate in the limestone to make a solution. This solution contains calcite and as water runs in streams through the limestone pavement it deposits this calcite. Over long periods of time this calcite deposit builds into features such as stalactites and stalagmites that are found in the caverns eroded through this process.

Formula for carbonic weathering - H2CO3 + CaCO3 → Ca(HCO3)2

Sandstone is the second most common rock found in Ireland and can be found in the Magillicuddy Reeks Co. Kerry. It can also be used as a building material depending as some is soft and some is hard. It is usually permeable but this depends on the rate of compression of the sand grains in the rock. It is formed in two stages, sedimentation and cementation. A layer of sand accumulates as a result of sedimentation. This layer can form from the suspension layer in water settling to the bottom. or from sand in the air in a desert. After this first layer accumulates it is compressed by overlying layers and cemented by materials such as silica and calcium carbonate. The color of sandstone can alter depending on the area and individual materials found in it. Usually it is yellow/brown but in parts of America where iron oxide (rust) is a component in is a brick red. Similarly if manganese is a component in can have a purple hue.

This is a photo of the karst landscape in The Burren and the clints and grikes created through this chemical process.

Igneous Rock

The first form of rock that ever existed on the planet were igneous rocks. It forms 95% of the earth's crust and there are over 700 different types of igneous rocks on the planet. Igneous rocks, derived from the latin word ignus meaning fire, were formed when magma was forced to the earths surface (crust)then cooled and solidified thousands of years ago. Igneous rocks can be further divided into two groups, intrusive and extrusive.

Intrusive rocks were formed within the earth's crust and were surrounded by a pre- existing rock called a 'country rock' therefore they cooled slowly. Due to this, they formed large crystals. An example of an intrusive igneous rock commonly found in Ireland is granite such as that found in the Wicklow Mountains.

Extrusive rocks were formed when molten rock from the earth's mantle extrudes onto the surface as lava. The magma cools much quicker in the open air, or in most cases in the sea water and due to this one of the features of an extrusive rock is it has fine crystals. An example of an extrusive igneous rock found in Ireland would be basalt such as that that formed the Giant's Causeway in Northern Ireland.

Pumice is argueably one of the most unusual type of igneous rock. It is lightweight and formed when molten rock rapidly explodes out of a volcano. It quickly loses pressure and heat, causing it to form small bubbles on the surface giving it it's "spongey" appearance. Tuff is another strange rock formed from volcanic ash. Obsidian is a volcanic glass that forms very quickly and is used as a cutting tool.

This is granite , and this is basalt

Ireland's Bedrock

Ireland bedrock consists of various different type of rocks but to simplify this, they are grouped into rock types. These are the main rock types found in Ireland and the general areas in which they are found.

Granite - Wiclow, Connemara, Donegal

Limestone - Central Plains, The Burren, Cork, Kerry

Basalt - Antrim (The Giant's Causeway)

Marble - Kilkenny, Connemara

Sandstone - Cork, Kerry

Quartzite - Donegal, peak of Errigal Co. Donegal, peak of The Great Sugarloaf Co. Wicklow

Here is a map of the main bedrock in Ireland

Topics

I'm just going to quickly run through the main points of discussion for this blog.

• Overview of Ireland's bedrock
• Formation of igneous rock, intrusive and extrusive
• Formation of sedimentary rock - Formation of Metamorphic rock
• Interesting rock formations around the world
• The Burren, Co. Clare

Welcome geologists

Hello my name is Ana, and I am here to break it down (through weathering and erosion).Lol. This is my blog about rocks, enjoy! Rock on.