Rocks and the Rock Cycle Flashcards
Where are sedimentary rocks formed?
Near the surface of the earth.
Where can sedimentary rocks form?
Land, lake beds and beneath the sea
What are the layers in sedimentary rock called?
Strata
What process converts sediment layers into solid rock?
Lithification
What two ways does lithification occur?
- Compaction
- Cementation
Describe compaction.
As the grains are squeezed together by the weight of overlying sediments
Describe cementation.
As individual particles are bonded to one another by a cementing agent such as silica or calcium.
What are the three types of sedimentary rocks?
- Inorganic sedimentary rocks
- Organic sedimentary rocks
- Chemical sedimentary rocks
How are inorganic sedimentary rocks formed?
Are formed from sediments that were broken down by weathering and erosion of pre-existing rocks.
Name two common sedimentary rocks.
Sandstones and conglomerates
How are organic sedimentary rocks formed?
Are formed from the sediments that came from once living organisms, such as plants and sea creatures.
Name two common organic sedimentary rocks.
Limestone and coal
How are chemical sedimentary rocks formed?
Are formed from material that was carried in solution in lakes and seas.
Name two common chemical sedimentary rocks.
Gypsum and rock salt.
Give an example of a coarse-grained inorganic rock?
Sandstone
How is sandstone formed?
Formed when grains of quartz were deposited in layers on land or on the bed of a shallow sea.
What is quartz?
Sand particles
What two ways can deposits of quartz accumulate?
- Flood deposits
- Wind deposits
When was sandstone created in Ireland?
Roughly 350 million years ago.
What caused the sandstone to form in Ireland?
It was a result of flash flooding.
What happened to the Caledonian mountains?
Heavy rainfall eroded them, washing the eroded sediments into the bed of a shallow sea.
What does this sea bed make up now?
Much of the Munster Landscape
What did the sandstone contain?
High levels of iron oxide- gave it a reddish appearance
What substances helped bond the sediments together?
Iron and silica
What is this sandstone called?
Old Red Sandstone
How long did the old red sandstone remain submerged in the shallow sea?
Until approximately 250 million years ago.
How was the sandstone moved up from the sea bed?
The African and Eurasian plates collided- causing the layers of sandstone and overlying limestone to buckle and uplifted.
What were the newly formed Munster mountains called?
The Armorican Mountains.
What did this process of folding create?
Parallel ridges of sandstone and valleys of limestone
What happened to the limestone valleys?
They were weathered and eroded downwards creating flat, fertile land between the ridge mountains
What has happened to form dolomite?
It has undergone a chemical change
What chemical change occurred in dolomite?
The calcium has been replaced by magnesium
What colour is dolomite?
Varies in colour from white to grey or pink
Where is dolomite found in Ireland?
Found among the limestone of the south of Ireland
What is chalk?
Pure, soft, white-coloured limestone
Where did it used to be found?
It once covered Ireland, but it has been eroded.
Where has the chalk not been eroded?
The Antrim-Derry Plateau, where it is protected by a layer of basalt
What is limestone an example of?
An organic rock
How is limestone formed?
From the compressed remains of sea creatures.
