Types of Rocks and the Rock Cycle Flashcards
What is a rock? Name its three types.
A rock is a mixture of minerals. It is of three types; igneous rocks, sedimentary rocks and metamorphic rocks.
Which types of rocks are had? Which ones are soft? How do hard rocks/soft rocks form?
Igneous rocks - hard
Sedimentary rocks - soft
Metamorphic rocks - hard
Hard rocks go through extreme temperature and pressure, and hence their particles are very densely packed making them very hard. However, soft rocks are formed layer by layer making them softer.
What are igneous rocks? Name its two types.
Igneous rocks, also known as primary rocks of the rocks formed via magma solidification. It is of two types, intrusive igneous rocks and extrusive igneous rocks next.
How do intrusive igneous rocks form?
When magma cools and solidifies below the Earth surface, it forms intrusive igneous rocks. We know about these rocks due to weathering and erosion. They are stronger as they are put under more pressure. They form large crystals and have a slow cooling process.
Examples of intrusive igneous rocks are granite and diorite which are used as building material as they are extremely resistant to weathering and erosion.
How do extrusive igneous rocks form?
When magma cools and solidify above the Earth surface, it forms extrusive igneous rocks. The formation of exclusive rocks involves two processes, cooling and solidification. They form fine crystals and have a quick cooling process.
Example examples of exclusive igneous rocks are Pumice (used to create light weight concrete) and obsidian (used to create jewellery or knives).
What are sedimentary rocks? Name its three types and give an example.
Sedimentary rocks, also known as, stratified rocks are a type of rock that is formed from pre-existing rocks or pieces of once living organisms.
The himalayan mountain range is made up of sedimentary rocks/sediments. The sedimentary rocks are created when the plates collide and use pressure to push the sediments together.
How do sedimentary rocks form?
The formation of sedimentary rocks involves several processes.
Weathering and Erosion - Weathering and erosion cause the breaking down of previous rocks to form sediments. The settlements are transported by erosion to the ocean bed.
Deposition - These sediments get deposited on the ocean bed
Sedimentation - The eroded materials begin to settle in the water
Compaction - With time, more layers, pile up and press down on the previous layers
Further compaction - More layers (strata) and further compaction forces water out of the layers
Cementation - Salt crystals glue the layers together. The rock mass formed is sedimentary.
Different sediments form from different types of sedimentary rocks.
What happens as the layers compress during the formation of sedimentary rocks?
- Temperature increases as heat gets trapped between the layers.
- Pressure increases as ocean beds are at depth. The deeper we go, the more pressure.
- For sedimentation to occur, we need high pressure and temperature, so sedimentation can only occur in the ocean floor and similar places.
Briefly describe each type of sedimentary rock.
- Clastic Sedimentary Rocks - mainly made of sand particles. For example, sandstone and conglomerate.
- Bio - chemical sedimentary rocks - made from the accumulation of shell, coral and debris. For example, limestone
- Organic sedimentary rocks - mainly made from plant debris. For example, coal.
What are metamorphic rocks? Name its two types
Metamorphic rocks are a type of rocks that form from the transformation of existing rock types in a process known as metamorphism. All rock types can form metamorphic rocks. The two types of metamorphic rocks are foliated and non-foliated metamorphic rocks.
What is metamorphism?
Metamorphism refers to the alteration of the composition or structure of a rock by heat, pressure, or to a hot mineral rich fluid (magma).
What are foliated metamorphic rocks?
Foliated metamorphic rocks are metamorphic rocks which have a layer or bandit appearance due to the alignment of minerals under pressure. They formed through regional metamorphism often in a mountain building process. For example, slate, gneiss and schist.
What is regional metamorphism?
Regional metamorphism is the type of metamorphism where the rock is subjected to extreme heat and pressure over a large area due to tectonic forces. Instead of melting, the minerals realign, and re-crystallise, changing the rocks composition, and forming a metamorphic rock.
What are non-foliated metamorphic rocks?
Non-foliated metamorphic rocks are metamorphic rocks which do not have a layer or banded structure. They form under high-pressure and temperature, but without directed stress, leading to a uniform texture. They typically form through contact metamorphism. Examples include marble quartz and hornfels.
What is contact metamorphism?
Contact metamorphism is a type of metamorphism where the rock comes into contact with extreme heat of the rising magma, the country rocks (pre-existing rocks surrounding an intrusion of magma), instead of melting, undergo chemical changes due to high temperature, forming metamorphic rocks.
Differentiate between contact and regional metamorphism.
- The relative scale of contact metamorphism is small, whereas the relative scale of regional metamorphism is large.
- The main driver of contact metamorphism is heat, whereas the main driver of regional metamorphism is pressure.
Define:
1. Protolith
2. Country Rocks
- Protolith - The original rock before undergoing the process of metamorphism
- Country rocks - Old rocks under the surface
Describe the rock cycle in points?
The rock cycle is how rocks change over time.
- Igneous rocks form when hot magma cools.
- Weathering and erosion break rocks into tiny pieces.
- Sedimentary rocks form when these pieces get pressed together.
- Metamorphic rocks form when heat and pressure change rocks.
- Melting turns rocks into magma, starting the cycle again.
