Sedimentary Rocks 30 Flashcards
Two irish examples
Limestone - burren Co.Claire
Sandstone - Co.Cork
When are rocks formed
Formed when sediments at the bottom of the sea are compressed,compacted and cemented together naturally
What do sediments include
Small rock particles
Sand,clay
Plant and animal remains
What is lithification
Process of compaction and cementation where sediments are compressed together by the weight of over lying sediments
Silica and calcite stick them together
What two minerals stick rocks together
Calcite and silica leak from grains and stick sediments together to form solid rock
What are strata
Layers of rocks
These strata are separated by bedding planes
What are bedding planes
Horizontal cracks between layers of sedimentary rocks
What are joints
Vertical lines of weakness throughout limestone that were formed when rock was compressed by plate movements
How does water move through limestone
Down through joints
Alone bedding plants and again down through joints
What is stratification
Series of layers (strata)
Name the 3 sedimentary rocks
Organic, inorganic and chemically
What are organic rocks made up of
Dead plant and animal remains compacted together from calcite from shells and bones
Two examples of organic rocks
Limestone
Chalk (a pure white form of limestone) Giants causeway
What is chalk and where can it be found
Chalk is a pure white form of limestone
Giants causeway Co.Antrim
What are inorganic rocks made of
Form from the lithification of rock fragments
Compacted by silica from remains of pre existing rocks
Two examples of inorganic rock
Sand stone Co.cork
Mudstone
Shale (Co.Claire)
How and when was irish old red sand stone formed
> 400-350 million years ago
Ireland lay 30 degrees of equator, hot desert climate
when huge river carrying sediments that would eventually turn into sandstone flowed over this dry landscape Old red sandstone was formed
can be found in cork and Kerry mountains
How are chemically formed rocks formed
> water from sea/enclosed lakes evaporates
>sediments are compacted by weight of mud and sand and stratified rocks are formed
Example of chemically formed rock and use
Gypsum Co.Cavan
Used in manufacturing of cement
What colour is limestone and what is a use
Grey
Used in cement
How is limestone weathered
Weathered by rainwater in a process called carbonation
As rain fall through athmosphere it soaks through soil is absorbs carbon dioxide
This forms a weak carbonic acid
This slowly dissolves the limestone
Where can weathered limestone be seen
Evident in karst areas eg burren co.claire where limestone rock has been exposed
How is limestone pavement formed
Joints are widened and deepened to become grikes
The many slabs separating these grikes are called clints
This feature is a limestone pavement
What happens when a river flows over limestone pavement
Disappear through enlarged joints called swallow holes
As the rain moves through the permeable limestone it is
Dissolving rock (carbonation)
Eroding (hydraulic action)
What may happen to bedding plane over time
May enlarge into caves and caverns
What do limestone caves contain
Many dripstone features formed by water containing dissolved limestone Stalactites- ceiling Stalagmites - ground Pillars - they both meet Allwee caves Co.claire
How are blow holes formed
Joints may be eroded by compressed air which will form a blow hole
Diagrams
Lithification
Coast
