Metamorphic Rocks

David Akerman

8 Jun 202002:28

Summary

TLDRThis video script explains the rock cycle, focusing on how sedimentary rocks transform into metamorphic rocks under heat and pressure. It differentiates between regional metamorphism, affecting large areas with intense pressure, and contact metamorphism, which occurs near magma with less intense pressure. Examples like shale turning into slate, then to schist, and the formation of non-foliated metamorphic rocks like marble are discussed. The script concludes by reiterating the rock cycle's importance and encourages viewers to engage with related questions.

Takeaways

🪨 Sedimentary rocks form by piling up and creating layers of rock.
🔥 Over time, pressure and heat from Earth's interior change sedimentary rocks into metamorphic rocks.
🌍 Regional metamorphism happens over a large area, creating intense pressure that transforms rocks.
🌋 Contact metamorphism occurs when rocks are changed by heat from nearby magma with less intense pressure.
🛠️ Shale, a sedimentary rock, can transform through regional metamorphism into slate, phyllite, schist, and gneiss.
🔄 Heat and pressure cause minerals in metamorphic rocks to recrystallize and align, creating foliation.
🪶 Not all regional metamorphism results in foliation; for example, bituminous coal turns into anthracite coal without foliation.
🔥 Hornfels is an example of a rock formed only through contact metamorphism.
🏔️ Some non-foliated rocks, like quartzite, marble, and metaconglomerate, can be formed by both regional and contact metamorphism.
🔄 The rock cycle involves magma cooling into igneous rock, which can break into sediments, compact into sedimentary rock, and transform into metamorphic rock under heat and pressure.

Q & A

What causes sedimentary rocks to transform into metamorphic rocks?
-Sedimentary rocks transform into metamorphic rocks due to the tremendous pressure and heat from Earth's interior.
How does regional metamorphism differ from contact metamorphism?
-Regional metamorphism occurs over a large area with intense pressure, while contact metamorphism happens with less intense pressure due to contact with magma.
What is shale and how does it change through regional metamorphism?
-Shale is a sedimentary rock that changes through increased regional metamorphism into slate, then phylite, schist, and finally gneiss through increased heat and pressure.
What is foliation and how does it occur in metamorphic rocks?
-Foliation is the alignment of minerals to form bands of the same minerals. It occurs in metamorphic rocks due to recrystallization and exposure to new heat.
Can you provide an example of a metamorphic rock that does not have foliation?
-Bituminous coal, when it changes into anthracite coal, is an example of a metamorphic rock that does not have foliation.
What is contact metamorphism and how does it affect rocks?
-Contact metamorphism is a type of metamorphism where rocks are changed by the heat from nearby magma, leading to the formation of rocks like hornfels.
What are some metamorphic rocks that can be formed by both regional and contact metamorphism?
-Metamorphic rocks like quartzite, marble, and metaconglomerate can be formed by both regional and contact metamorphism.
How does the rock cycle begin with igneous rocks?
-The rock cycle begins with igneous rocks when magma cools and solidifies.
What happens to sedimentary rocks as they are buried and subjected to pressure?
-As sedimentary rocks are buried and subjected to pressure, they compact and cement together to form sedimentary rocks.
How can metamorphic rocks revert back to the beginning of the rock cycle?
-With enough heat and pressure, metamorphic rocks can melt back into magma, which can then cool and solidify to start the rock cycle again with igneous rocks.
What is the significance of the rock cycle in understanding Earth's geological processes?
-The rock cycle is significant as it illustrates the continuous transformation of rocks through various geological processes, providing insight into Earth's dynamic nature.

Outlines

00:00

🌋 Formation of Metamorphic Rocks

This paragraph explains the process of sedimentary rock transformation into metamorphic rocks due to pressure and heat. It highlights two types of metamorphism: regional and contact. Regional metamorphism occurs over a large area with intense pressure, causing rocks like shale to transform into slate, phylite, schist, and eventually gneiss. Contact metamorphism happens when rocks are near magma, leading to less intense pressure and can result in rocks like hornfels. The paragraph also discusses the recrystallization of minerals and the formation of foliation in metamorphic rocks. It concludes with a brief overview of the rock cycle, explaining how rocks can change from one type to another through various geological processes.

Mindmap

Keywords

💡Sedimentary Rocks

Sedimentary rocks are formed by the accumulation and cementation of mineral and organic particles on the Earth's surface. They often form visible layers or strata, which are a key feature in the rock cycle discussed in the video. The script mentions that these rocks pile up to create layers, which can eventually become metamorphic rocks under heat and pressure.

💡Metamorphic Rocks

Metamorphic rocks result from the transformation of existing rock types, often sedimentary or igneous rocks, due to heat, pressure, or mineral exchange with fluids. The video explains that these rocks can form through regional metamorphism, which occurs over a large area, or contact metamorphism, which happens near magma. Examples given include shale changing into slate, then to phylite, schist, and finally to gneiss.

💡Regional Metamorphism

Regional metamorphism is a process where rocks are subjected to uniform heat and pressure over a large area, leading to the formation of metamorphic rocks. The video script describes how shale, a sedimentary rock, undergoes a series of transformations into different metamorphic rocks through increased regional metamorphism.

💡Contact Metamorphism

Contact metamorphism occurs when rocks are heated by the proximity of magma, causing them to change without the intense pressure associated with regional metamorphism. The script uses the example of hornfels, which is formed only through contact metamorphism.

💡Shale

Shale is a type of sedimentary rock composed of mud that has been compacted over time. In the video, shale is used as an example of a rock that undergoes metamorphism, changing into various other rocks such as slate, phylite, schist, and gneiss, depending on the degree of heat and pressure it experiences.

💡Foliation

Foliation is a texture in metamorphic rocks where minerals are aligned in a layered or banded arrangement due to the influence of pressure and heat. The script explains that not all metamorphic rocks exhibit foliation, but it is a common feature in those that have undergone regional metamorphism.

💡Recrystallization

Recrystallization is the process by which minerals in rocks are altered into new crystal forms due to changes in temperature and pressure. The video script mentions that minerals in shale recrystallize as they are subjected to new heat and pressure, leading to the formation of different rock types.

💡Bituminous Coal

Bituminous coal is a sedimentary rock that can transform into anthracite coal, a type of metamorphic rock, through heat and pressure. The video script notes that this transformation does not involve foliation, which is a key difference from other types of metamorphic rocks.

💡Hornfels

Hornfels is a type of metamorphic rock that forms from the contact metamorphism of shale, mudstone, or volcanic rocks due to the heat from nearby magma. The script specifically mentions that hornfels is formed only through contact metamorphism.

💡Marble

Marble is a metamorphic rock that forms from the metamorphism of limestone, which is a sedimentary rock. The script includes marble as an example of a metamorphic rock that does not exhibit foliation and can be formed through both regional and contact metamorphism.

💡Rock Cycle

The rock cycle is a conceptual model that illustrates the transitions through which rocks can move as they change from one type to another. The video script summarizes the rock cycle, explaining how rocks can transform from igneous to sedimentary, to metamorphic, and back to igneous through processes such as melting, cooling, compaction, and metamorphism.

Highlights

Sedimentary rocks form layers that, under pressure, transform into metamorphic rocks.

Pressure and heat from Earth's interior cause the transformation of sedimentary rocks.

Regional metamorphism occurs over a large area with intense pressure.

Contact metamorphism happens with less intense pressure due to contact with magma.

Shale, a sedimentary rock, undergoes a series of changes through regional metamorphism.

Shale changes to slate, then to phylite, schist, and finally to gneiss with increased heat and pressure.

Minerals in shale recrystallize due to exposure to new heat during metamorphism.

Foliation is the alignment of minerals, forming bands of the same minerals.

Not all regional metamorphism results in foliation, as seen in the case of bituminous coal to anthracite coal.

Contact metamorphism can create rocks like hornfels, which are formed only through contact with magma.

Port site marble and meta conglomerate are metamorphic rocks formed without foliation.

The rock cycle involves the transformation of rock into magma, then igneous rock, sedimentary rock, and back to metamorphic rock.

Heat and pressure cause the crystals in metamorphic rocks to reform.

With enough heat and pressure, metamorphic rocks can melt back into magma.

The rock cycle can start over again with igneous rock if magma cools.

A rock cycle activity is part of the final work for the course.

Students are encouraged to answer questions in the forum correctly to understand the rock cycle.

The lecture concludes with a reminder to have a great day.