Rock Cycle Flashcards
What are rocks?
Rocks are solid materials occurring in the earth’s crust, composed of one or more minerals. They vary according to their:
Hardness: resistance to weathering and Erosion
Shape: how they were laid down e.g limestone in strata
Texture: how rough or smooth to feel
Mineral content: the minerals that make up the rock e.g quartz, gypsum, calcite
Origin: where and how they were created
Density: amount of rock comparative to the space it takes up
What is the rock cycle? (Also know the diagram and the different processes)
It describes the earth’s natural processes that cause igneous, sedimentary and metamorphic rocks to be formed, changed, destroyed and recycled.
What is lithification?
Lithification is when sediments are compacted, compressed and cemented together to form solid rock
What is compaction?
When sediments are squeezed together by the weight of overlying layers, including water
What is cementation?
Cementation is when water evaporates from dissolved materials, creating crystals that glue sediments together
What is magma?
Magma is hot, liquid rock formed when earth’s crust is sub ducted and broke down in the mantle
What are plutonic rocks?
Plutonic rocks, also known as intrusive igneous rocks, are formed deep beneath earth’s surface
What are volcanic rocks?
Volcanic rocks, also known as extrusive igneous rocks, are formed on or near earth’s surface
What are igneous rocks?
Igneous rocks are formed when magma from the mantle cools and solidifies within the earth’s crust (intrusive) or on the earth’s surface (extrusive) . Basalt and granite are two types of igneous rocks
What is basalt?
Basalt is a volcanic igneous rock, which can be found in the Antrim Derry plateau or the Giant’s Causeway. It is usually dark grey to black in colour and is smooth textured. It is formed at divergent plate boundaries.
How is basalt formed?
65 million years ago, the North American and Eurasian plates separated, creating the Atlantic Ocean. Fissures were created on the crust, allowing lava with low silica content to pour out slowly. The lava cooled and hardened rapidly for in a basic igneous rock.
At the giant’s causeway, the basalt contracted and split into hexagonal columns due to the uniform mineral content .
What is basalt used for?
Cut basalt can be used in floor tiles, and crushed basalt can be used as road clippings
What is granite?
Granite is a plutonic, igneous rock which can be found in the Wicklow mountains. It is typically grey in Ireland, but the Co,our may vary depending on the mineral content. Is is coarse grained in texture and is a hard, durable rock. Is it formed at convergent plate boundaries.
How is granite formed?
40l million years ago, the Eurasian and North American plates collided, forming the Wicklow mountains. Molten magma with a silica content of nearly 70% intruded into a large space in the up folds beneath the earth’s surface. The magma cooled slowly as it was protected from the elements of weather by layers above it.
Over time, it formed a domed mass of granite known today as the Leinster Batholith . Large crystals such as mica, feldspar and quartz were formed in the granite.
What is granite used for?
Granite can be used in construction of buildings and bridges and polished granite can be used in countertops and floor tiles
What is acidic and basic igneous rock?
Acidic igneous rock is rock with a silica content of more than 55%, and basic igneous rock is rock with a silica content of less than 55%.
What is sedimentary rock?
Sedimentary rock is formed from the particles of dead animals, decayed plants, sea creatures and broken down rocks. They are stratified and separated by horizontal gaps called bedding planes. They generally form, on the beds of rivers, lakes and oceans. There are two types of sedimentary rock: organic and inorganic
What is organic and inorganic sedimentary rock?
Organic rock is rock formed from once living things and decayed plants . Inorganic rock is formed from broken down sediments of other rocks
What is limestone?
Limestone is an organic sedimentary rock, and can be found in the Burren Co Clare. Different types of limestone can be identified by its colour and hardness. For example, chalk is white in colour, pure limestone and easily eroded. Carboniferous limestone, is over 50% calcium carbonate, is grey in colour and is more resistant to erosion. Limestone is the most common rock type in Ireland.
What can limestone be used for?
Limestone can be used in making glass and cement
How is limestone formed?
It began forming 300 million years ago, when Ireland was in a warm, shallow ocean close to the equator. Over time, bones, shells and Dead Sea creatures built up on the sea floors. Other sand deposits and mud particles built up on top of that, and the weight of these materials lithified everything together. Calcium carbonate cemented the bones of the Dead Sea animals, preserving them as fossils in the rock.
Limestone forms in different layers of strata. The lower down the strata is in the rock, the older it is. Strata are separated by bedding planes and cracks called joints, which makes limestone a permeable rock, as water can pass through these cracks.
What is sandstone?
Sandstone is an inorganic sedimentary rock which can be found in the Caha mountains, or the Macgillycuddy’s Reeks. Old red sandstone is typically red in colour due to the presence of iron oxide. Old red sandstone is the most common type of sandstone found in Ireland, and sandstone is Ireland’s second most common rock type.
How was sandstone formed?
Old red sandstone formed 380 million year ago when Ireland was south of the equator with a desert climate. Rocks broken down by weathering and erosion were transported by flash floods and only Caledonian mountains were visible above water. Then the fine sediments were deposited in strata on the sea bed and were compressed together, and cemented by silica, calcium carbonate and iron, forming solid rock. Sock sandstone contains preserved sea creatures as fossils.
How is sandstone used?
It can be used as a decorative stone in sculptures, headstones or as paving stones
Know other types of sedimentary rocks (look at book for full descriptions)
What is coal?
Coal is an organic sedimentary rock formed when decayed vegetation is compacted by deposits of sand, silt and clay before it has decayed. It can be found in Arigna, Co. Roscommon
What is Breccia?
Breccia is a sedimentary rock composed of large, angular fragments, compacted and cemented together by smaller sediments
What are metamorphic rocks?
They are formed when igneous or sedimentary rocks are subjected to great heat and or pressure. They are formed in one of two ways:
Regional metamorphism (dynamic): friction at convergent plate boundaries creates great heat and pressure which changes the composition and texture of rocks over a large area e.g a zone of subduction
Contact metamorphism (thermal): rising molten magma changes the composition of rocks in a small area e,g a volcanic intrusion
What is an aureole?
A zone where parent rock changes to metamorphic rock
What is marble?
Marble can be found in Connemara, County Galway and is a coarse-grained, hard rock. It is commonly polished to give it a smooth texture
How is marble formed?
Marble is a crystalline rock formed when limestone or chalk changes as a result of regional metamorphism. It is formed at convergent plate boundaries, where limestone is changed by great heat and pressure caused by friction. Calcite minerals in limestone are re-crystallised creating a denser rock composed of interlocking calcite crystals. Greater levels of metamorphosis create larger crystals.
Pure white marble (e.g from Carrera, Italy) is pure limestone with no impurities. Impurities comer east in different ways to heat, causing variations in colour. Green ,Ariel can be found in Galway, red marble in cork and black marble in Kilkenny.
What can marble be used for?
Marble is used as a decorative stone in building as well as in sculptures
What temperatures do metamorphosis occur?
Between 250 and 850 degrees celcius
What is quartzite?
Quartzite is a medium grained, hard rock which varies in colour and can be found at the Hill Of Howth Co. Dublin. It is formed when sandstone changed by contact metamorphism. 400 mya, the Eurasian and North American plates collided during the Caledonian folding period. Molten magma filed the spaces beneath the upholds of the earth’s surface and came into contact with sandstone. The sandstone grains chemically changed into quartz. The grains also contained silica which cemented the rock. Extreme heat and pressure in the surrounding area caused quartzite to form.
What can quartzite be used for?
Quartzite can be used in countertops and to surface roads.
