What is magma and how is magma formed? | The difference between magma and lava

Summary

In this video, viewers learn about magma—its composition, types, and how it forms. Magma, a hot mixture of molten rocks, is classified into three types: basaltic, andesitic, and rhyolitic, each with different silica content, gas levels, and viscosity. The video explains how magma forms through processes like partial melting, decompression melting, and flux-induced melting. It also highlights the difference between magma and lava, emphasizing that lava is magma that has reached the Earth's surface. The video invites viewers to explore more about Earth’s geological wonders in future content.

Takeaways

• 🌋 Magma is a hot mixture of molten and semi-molten rocks flowing deep beneath the Earth's surface.
• 💡 Magma consists of inorganic components like minerals, rocks, and dissolved gases embedded in the hot liquid base (melt).
• 🧪 There are three types of magma: basaltic, andesitic, and rhyolitic, classified by their silica content and other minerals.
• 🔥 Basaltic magma has the lowest silica content, highest temperature, lowest gas content, and lowest viscosity among the three types.
• 🧱 Andesitic magma has moderate silica content, moderate temperature, moderate gas content, and higher viscosity compared to basaltic magma.
• ⛰️ Rhyolitic magma has the highest silica content, the lowest temperature, highest gas content, and highest viscosity.
• 🌍 Magma forms deep beneath the Earth’s surface, typically in the lower crust and upper mantle, through partial melting, decompression melting, or flux-induced melting.
• 🔄 Decompression melting occurs when mantle rocks move upward, reducing pressure, and causing the rocks to melt without changing temperature.
• 💧 Flux-induced melting happens when substances like water lower a rock’s melting point, causing it to melt more easily.
• 🔥 The key difference between magma and lava is that magma becomes lava once it reaches the Earth's surface, typically during volcanic eruptions.

Q & A

What is magma?

Magma is a hot, viscous material made up of molten and semi-molten rocks, minerals, and dissolved gases, found deep beneath the Earth's surface.

What are the main types of magma?

The main types of magma are basaltic magma, andesitic magma, and rhyolitic magma, classified based on their silica content and other chemical properties.

What is the difference between basaltic, andesitic, and rhyolitic magma?

Basaltic magma has the lowest silica content (45-55%), high in iron, magnesium, and calcium, and low viscosity. Andesitic magma has a moderate silica content (55-65%) and viscosity, while rhyolitic magma has the highest silica content (65-75%) and viscosity, with lower levels of iron, magnesium, and calcium.

Where does magma originate from?

Magma originates from deep beneath the Earth's surface, in the lower crust and upper mantle, where high pressures and temperatures cause rocks to melt.

How is magma formed through partial melting?

Partial melting occurs when only some minerals in a rock melt due to differing melting points of the minerals, with the ones with lower melting temperatures melting first.

What is decompression melting and how does it form magma?

Decompression melting occurs when rocks in the mantle move upward, experiencing lower pressure, which allows them to melt even without a change in temperature.

What is flux-induced melting?

Flux-induced melting happens when certain elements, like water or carbon dioxide, lower the melting point of rocks, enabling them to melt and form magma.

What is the difference between magma and lava?

Magma is the molten rock beneath the Earth's surface, while lava is magma that has reached the Earth's surface through a volcanic eruption or vent.

What are the characteristics of basaltic magma?

Basaltic magma has low silica content, low viscosity, high temperature, and contains high levels of iron, magnesium, and calcium, making it the least gaseous of the three magma types.

Why does magma remain in a fluid state?

Magma remains fluid due to a combination of high temperature and pressure conditions found deep within the Earth's mantle and lower crust.

Outlines

00:00

🔥 Understanding Magma and Its Types

The first paragraph introduces magma, a hot mixture of molten and semi-molten rocks beneath the Earth's surface. It explains that magma consists of minerals, rocks, and dissolved gases. The paragraph outlines three types of magma: basaltic (low silica, high in iron, magnesium, and calcium), andesitic (moderate silica, with a balanced composition of other elements), and rhyolitic (high silica, low iron, and magnesium). Each type varies in temperature, viscosity, and gas content, with basaltic being the hottest and rhyolitic being the most viscous. The paragraph sets the stage for exploring the origins and formation of magma.

05:00

🔬 How Magma Stays Fluid and Earth's Layers

This section briefly mentions Earth's layers—inner core, outer core, mantle, and crust—to introduce the concept of magma's origin deep beneath the surface. It highlights that magma remains fluid due to high pressure and temperature at these depths. The paragraph teases further discussion on magma formation processes, setting up an explanation of the different mechanisms responsible for its creation, such as partial melting, decompression melting, and flux-induced melting.

🧊 The Process of Partial Melting

Here, partial melting is explained as a process where some minerals in rocks melt due to heat, while others remain solid because of their higher melting points. Magma forms as the lower-melting-point minerals melt and flow upwards from the mantle, transferring heat to other rocks, causing additional melting. The concept of a phase diagram is introduced, which will be explained further in subsequent sections. This phase diagram visually represents material states under varying temperatures and pressures.

📉 Phase Diagrams and Decompression Melting

The paragraph begins with a simple explanation of phase diagrams, showing how materials change from solid to liquid or gas under different temperatures and pressures. It then discusses decompression melting, where pressure decreases as rocks move upwards or through thinner crust, allowing solid mantle rocks to melt even without an increase in temperature. This is particularly common in rift zones where the Earth's crust is thinner.

💧 Flux-Induced Melting and Magma’s Journey to Lava

Flux-induced melting is described here, where water or gases like carbon dioxide lower the melting point of rocks, leading to the creation of magma. Once partial melting begins, magma continues to rise and can eventually break through the Earth's surface. When this happens, it is no longer called magma but lava. The paragraph concludes by distinguishing between magma and lava, with a promise of future videos on volcanic rocks and diamonds carried by magma to the Earth’s surface.

Keywords

💡Magma

Magma is a hot, viscous mixture of molten and semi-molten rocks that exists beneath the Earth's surface. It contains minerals, rocks, and dissolved gases, forming the core material discussed in the video. The video explains magma's composition and the different ways it is formed deep in the Earth's crust and mantle.

💡Basaltic magma

Basaltic magma has the lowest silica content (45-55%) and is rich in iron, magnesium, and calcium. This type of magma has the lowest gas content and viscosity, making it the most fluid of the three types discussed. The video uses basaltic magma as an example to explain how different magma compositions affect its properties, such as temperature and viscosity.

💡Andesitic magma

Andesitic magma contains 55-65% silica and has moderate levels of iron, magnesium, and gases. It has a lower temperature and higher viscosity compared to basaltic magma. The video highlights how the variation in silica content affects the viscosity and temperature, explaining why andesitic magma behaves differently from basaltic magma.

💡Rhyolitic magma

Rhyolitic magma has the highest silica content (65-75%) and is rich in potassium and sodium but low in iron and magnesium. It also has the highest viscosity and lowest temperature of the three magma types. The video uses rhyolitic magma to illustrate the effect of high silica content on the magma's thickness and temperature.

💡Viscosity

Viscosity refers to a fluid's resistance to flow. In the context of magma, the video explains how viscosity varies based on the magma's composition, especially its silica content. For example, basaltic magma has low viscosity, while rhyolitic magma has high viscosity, affecting how easily magma flows and erupts from the Earth's surface.

💡Partial melting

Partial melting is a process where only some minerals in a rock melt due to varying melting points. The video explains this mechanism as a key process in magma formation, where certain minerals in the mantle or crust melt, while others remain solid. This allows magma to form and rise through the Earth's layers.

💡Decompression melting

Decompression melting occurs when the pressure on solid mantle rocks decreases, allowing them to melt without a significant temperature change. The video uses this concept to explain how magma forms in areas with reduced pressure, like rift zones, despite stable high temperatures.

💡Flux-induced melting

Flux-induced melting happens when water or gases like carbon dioxide lower the melting point of hot rocks, causing them to melt. The video explains how this process allows magma to form when these 'fluxes' are present, facilitating partial melting and the rise of magma to the Earth's surface.

💡Earth's layers

The Earth's layers include the inner core, outer core, mantle, and crust. Magma is formed in the lower crust and upper mantle due to high pressure and temperature. The video provides a brief overview of the Earth's layers to help the audience understand where magma originates and the environmental conditions that influence its formation.

💡Lava

Lava is magma that reaches the Earth's surface during volcanic eruptions or through vents. The video distinguishes magma from lava, explaining that once magma exits the Earth, it becomes lava, cooling to form volcanic rocks and glass. This distinction is a key point towards the end of the video, helping viewers understand the transition between magma and lava.

Highlights

Introduction of magma as a hot, viscous mixture of molten and semi-molten rocks beneath the Earth's surface.

Magma consists of inorganic components such as minerals, rocks, and dissolved gases embedded in a hot liquid base.

Classification of magma into three types: basaltic, andesitic, and rhyolitic based on their chemical composition.

Basaltic magma has the lowest silica content (45-55%), high iron, magnesium, and calcium, low viscosity, and the highest temperature.

Andesitic magma contains a higher silica content (55-65%), moderate amounts of minerals, and has moderate gas content and viscosity.

Rhyolitic magma has the highest silica content (65-75%), is low in iron, magnesium, and calcium, and has the highest viscosity but lowest temperature.

The viscosity of magma is influenced by its temperature and composition, affecting how it moves.

Magma forms in the lower crust and upper mantle under high pressures and temperatures, allowing it to remain fluid.

Magma formation mechanisms include partial melting, decompression melting, and flux-induced melting.

Partial melting occurs when only some minerals in a rock melt due to different melting points of the minerals.

Decompression melting happens when pressure decreases on mantle rocks, causing them to melt without temperature changes.

Flux-induced melting involves lowering a rock's melting point with the addition of water or other gases.

Phase diagrams are introduced to explain how different pressures and temperatures affect the state of materials.

Magma that reaches the Earth's surface is called lava, which can emerge during volcanic eruptions or through other vents.

Lava cools to form volcanic rocks and volcanic glass, key materials in understanding volcanic processes.

Transcripts

There is a super hot mixture of molten and semi-molten rocks that flows deep beneath the Earth's  

surface, and it is called magma. But what exactly  is magma? And how and where does it come from?  

In today's video, we'll learn what magma is, what  types of magma there are, and how magma is formed.  

And if you stay until the end, I will explain  what is the difference between magma and lava.  

First, let's learn about the composition of magma.  Magma is a hot, viscous material that consists of  

inorganic components such as minerals and rocks,  as well as dissolved gases, all embedded in the  

melt, which is the hot liquid base of the magma.  The composition of the magma depends on the type  

of magma that we're talking about. Depending on  the chemical composition of the magma, we can  

classify magma in three different categories. These  categories are: basaltic magma, andesitic magma, and  

rhyolitic magma. Let's start with basaltic magma.  Basaltic magma has the lowest concentration of  

silica, about 45-55 wt% (weight percentage), and it  is high in iron, magnesium, and calcium, and low  

in potassium and sodium. Basaltic magma also has  the lowest gas content and the lowest viscosity  

of the three types of magma. It's also the magma  with the highest temperatures. The second type of  

magma is andesitic magma. This one has a higher  weight percentage of silica than the basaltic  

magma, about 55-65 in weight percentage, and it  has moderate amounts of iron, magnesium, calcium,  

potassium, and sodium, as well as moderate amounts  of gases. Andesitic magma has a lower temperature  

and a higher viscosity than basaltic magma. Finally,  we have the rhyolitic magma, which has the highest  

weight percentage of silica, of around 65-75,  and it is low in iron, magnesium, and calcium, and  

high in potassium and sodium, and it also has  a higher gas content. Rhyolitic magma has the  

lowest temperature of all the different magma  types, and it has the highest viscosity. There  

you have it - the different types of magma and their  characteristics. One of their characteristics was  

the viscosity of the magma, which is a property  that describes a fluid. So how come magma stays  

fluid? To find out the answer to this question  let's first have a look at the Earth's layers.  

Earth consists of four main layers: the inner  core, the outer core, the mantle, and the crust.  

This preview of Earth's layers is enough for now,  but if you're interested in learning more about  

these layers I'll discuss ask them in more details  in a future video. Now, going back to the magma, it  

originates deep beneath the Earth's surface, in  the lower crust and the upper mantle. At those  

depths, the magma experiences high pressures  and temperatures, and it is fluid because of  

the different combinations of temperature, pressure,  and some other factors we'll discuss in the next  

section, where we learn how magma is formed.  There are different mechanisms through which  

magma is formed. Thus, magma can form through  partial melting, decompression melting, or flux-induced  

melting. Let's now discuss each of these  mechanisms, and see the differences between the  

different magma formation processes. First we'll  talk about partial melting. Magma forms through  

the heat-induced melting of the rocks that are  present in the upper mantle or the crust. In the  

case of partial melting, only some of the minerals  in the rock's composition are melting. But why is  

it that only some of the minerals melt? We know  that rocks contain different minerals in their  

composition, each made up of various combinations  of chemical elements. These minerals have different  

melting temperatures, and those with higher melting  temperatures will remain solid while those with  

lower melting temperatures will start melting.  This magma then moves upward from the mantle  

and can go all the way through the crust. On its  way up, as it encounters other rocks through the  

mantle and crust layers, it transfers some of  its heat to those rocks. The components of those  

rocks with lower melting temperatures than the  temperature of the magma will also start melting  

and join the magma flow. Before discussing  the next magma formation process, I need to  

introduce a new term called a phase diagram. A  phase diagram is a graphical representation  

of the physical state of a material as a function  of different temperature and pressure conditions.  

Here, you can see an example of a phase diagram of  a material showing the temperature and pressure  

ranges where the material is a solid, a liquid,  or a gas. This is just a simple representation  

of a phase diagram, but if you would like to learn  more about phase diagrams and how materials change  

from one physical state to another under different  temperature and pressure conditions, let me know in  

the comments below and I will be happy to create  a more detailed video about phase diagrams. Now  

we are ready to discuss the decompression  melting process for magma formation. Going  

back to this phase diagram example, if we look at  the blue star, at those temperature and pressure  

conditions, the material is a solid. If we kept the  pressure constant as we increase the temperature  

the solid melts, shown here by the red star. But we  don't need to increase the temperature to go from  

a solid to a liquid. Another way the solid could  melt is by decreasing the pressure that's acting  

on that solid. And you see here that even though  the temperature hasn't changed, by reducing the  

pressure we moved from a solid state to a liquid  state. This is what happens in decompression  

melting. The temperature in the Earth's mantle  is very high, but so is the pressure. And under  

those high pressures the mantle rocks are solid.  But if the rocks move upward, where the pressure  

is lower, or in the regions where the crust is  thinner, such as in rift zones, those rocks will  

experience a smaller pressure, and this reduction  in pressure will lead to a decompression melting  

of the rocks. Before talking about the third magma  formation mechanism, if you're enjoying this video  

please give it a thumbs up and subscribe to  my channel for more stories about the wonders of  

our planet. Now let's see what other factors, other  than temperature and pressure, can influence magma  

formation. The third mechanism we're talking  about is flux-induced melting. When a rock is  

hot, close to its melting point, but not quite  there yet, there are certain factors that could  

lower its melting point. A flux that can lower  the melting temperature of the rocks is water,  

but carbon dioxide and other gases can have the  same effect. When some water reaches the rock it  

lowers the melting temperature, and once the rock  starts melting we're back to the first process, and  

from here the partial melting takes over. And  now that we know what magma is, what types of  

magma there are, and how magma is formed, we still  have an important question to answer: what is the  

difference between magma and lava? Sometimes, the  magma breaks through the Earth's surface, either  

during a volcano eruption or through another vent.  The magma that's ejected and reaches the Earth's  

surface is now called lava. And when this lava  then cools, it forms volcanic rocks and volcanic  

glass. We'll be discussing volcanic rocks in  other videos, but for now that's all I wanted  

to share with you about magma. And if you want to  see what magma can bring with it to the surface,  

you might enjoy this other video I created about  diamonds and how magma transports them upwards  

to the Earth's crust. Thank you for watching,  and I hope to see you back here next time. Bye!