What Is Lava? Types, Structure & Role in Volcanic Eruptions
Our planet earth contains Volcanoes. The magma is present in the form of the crust. However, the volcanic eruption allows hot gases, molten lava, and some rock fragments.
All of them collaged to form an opening gate for the volcanic path. The volcanos are the reason that exposes the magma inside. Lava is a semi-fluid (molten rock) rock that happens due to volcano eruption (fissure).
You can also name the solidified molten rocks as lava. The molten lava flow may deposit at some cold and flat surface. This page can help you to know; how and why volcanoes erupt.
Speciality of Lava
You may find the temperatures of molten lava very high before they solidify. The temperature of molten lava varies from 1,300 to 2,200°F (700 to 1,200°C).
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The material behaves like a hot liquefied substance. It can flow like hot and molten syrup. Sometimes, it becomes incredibly stiff so that you won’t notice any further flowing. The viscosity of the lave will be higher when the silica content inside the lava is higher.
Mafic is also one type of lava. This lava is like ferromagnesian and dark-coloured like basalt. The Hawaiians have given a name to mafic called ‘pahoehoe’ and aa (or a’a).
Pahoehoe's lava can relax when it finds a smooth surface with mildly undulating or broadly hummocky soil. The liquid lava contains a thin and still-plastic crust that drags beneath it.
After some interval (a few days at least), it converts into rolls and folds like a tapestry. It will totally look like a bunch of twisted ropes lying around the soil.
In Hawaii, the lava called Pahoehoe flows are faded somehow. However, you can notice that liquid lava streams are getting the passage beneath a stronger (solidified molten lava) or short-term frozen surface.
Basaltic lava is also known as pahoehoe and has the margin of a flow. It is responsible for the sticking out of molten lava over one small toe or lobe after another.
Magma
Magma is a term that was used in ancient greek. This means thick unguent. Magma behaves like a molten rock that has some amount of volatile substances. All of these substances are present inside the core of the earth. Geologists may find these magma-contains lie below the earth’s surface.
Magma has a certain amount of chambers called magma chambers.
Inside each chamber, you can find an assemblage of suspended crystals, dissolved gases, and gas bubbles. The heat that endures within magma has a higher range of temperature. The temperature of magma lies between 1300 and 2400 degrees.
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It behaves as a molten or semi-molten state of all igneous rocks that combine together in a hot-liquefied form. Also, magma has other stuff besides molten rock, such as gas bubbles and suspended crystals.
Physical and Chemical Structure of Magma
The property of many magmatic liquids is they possess a higher amount of silica. The volcano has silicate melts in higher amounts. Each silicate compound is composed of certain earth-core materials such as:
Silicon
Oxygen
Aluminium
Iron
Magnesium
Calcium
Sodium
Potassium
A volcano has a physical behaviour that it melts during its eruption. So, certain factors are thereupon which it depends upon. Such factors are:
Atomic Structures of Comprised Materials
Temperature
Pressure
Material Composition
The viscosity of lava is also a fact and an identical property that stands superior for understanding magmas' behaviour. As we know, magma's viscosity depends on temperature; however, composition plays a higher role in understanding the magma than the temperature.
The silicon ion is an exciting kind of ion. It is small and highly charged within the active lava. Silicon ions have a higher capacity to merge with four oxygen ions to form a tetrahedral arrangement.
This arrangement forms around together to develop another smaller silicon ion. The name of the ion is ‘silica tetrahedron’.
Different types of magma are also there, which have a few amounts of silicon that exist within it. It contains an isolated form of silica tetrahedra. When the level of silicon rises, then the process of polymerization of silica tetrahedra begins partially.
This process tends to form different chains, sheets, and clumps of silica tetrahedra. All of them are joined by the bridging of oxygen ions. This is the process that helps increase the viscosity of the magma.
Reason Behind the Eruption of Volcanoes
The mantle of Earth is divided into certain portions. It has a certain amount of crust that is classified into different sections. All these classifications are based on individual seismology.
The conditions that help to promote the eruption of volcanoes are the continuous rise of temperature and pressure. These two factors can change the crust dramatically out of the mantle location. This process leads to continuous volcanic eruption as the temperature in that region should have crossed beyond 1000 o C.
FAQs on Lava Volcanic Ejecta: Physics Made Simple
1. What is lava and what is it primarily composed of?
Lava is molten rock that has been expelled from the interior of a terrestrial planet (like Earth) or a moon onto its surface. Before it reaches the surface, it is called magma. Lava is primarily composed of a silicate melt, which is a mixture of silicon and oxygen, along with other elements such as iron, magnesium, potassium, calcium, and sodium. As magma rises and erupts as lava, dissolved gases like water vapour and carbon dioxide escape.
2. What is the general term for all material expelled from a volcano during an eruption?
The all-encompassing term for any material forced out of a volcano during an eruption is volcanic ejecta, also known as tephra. This term includes a wide range of materials, such as molten lava, solid rock fragments of various sizes (pyroclasts), and volcanic gases.
3. What are the main types of lava, classified by chemical composition and viscosity?
Lava types are mainly classified based on their silica content, which directly affects their viscosity (resistance to flow):
Basaltic (Mafic) Lava: Has low silica content (around 50%), making it low in viscosity. It flows easily over long distances and typically forms shield volcanoes.
Andesitic (Intermediate) Lava: Contains medium levels of silica (around 60%). It has a higher viscosity than basaltic lava, flows more slowly, and builds up steeper composite or stratovolcanoes.
Rhyolitic (Felsic) Lava: Has high silica content (over 70%), making it extremely viscous. It barely flows and tends to pile up, forming lava domes. The trapped gases can lead to highly explosive eruptions.
4. What are the different types of solid volcanic ejecta, also known as pyroclasts?
Pyroclasts are solid fragments of volcanic material ejected during an explosive eruption. They are classified by size:
Volcanic Ash: The finest particles, with a diameter of less than 2 mm.
Lapilli: Pebble-like particles ranging from 2 mm to 64 mm in diameter.
Volcanic Bombs: Blobs of molten lava larger than 64 mm that are ejected and cool in the air, often forming streamlined shapes.
Volcanic Blocks: Solid, angular rock fragments larger than 64 mm that were torn from the volcano's structure during the eruption.
5. What is the key difference between magma, lava, and volcanic ejecta?
These terms describe volcanic material based on its location and form. Magma is molten rock that is stored beneath the Earth's surface. When this magma erupts and flows onto the surface, it is called lava. Volcanic ejecta is the broadest term, referring to all materials expelled during an eruption, which includes lava, solid pyroclasts like ash and bombs, and gases.
6. How does lava's composition influence the shape of a volcano and its eruption style?
The composition of lava is a primary factor in determining a volcano's structure and eruptive behaviour. Low-silica (basaltic) lava is very fluid, allowing it to travel far from the vent. This creates broad, gently sloping shield volcanoes with effusive, flowing eruptions. In contrast, high-silica (rhyolitic) lava is highly viscous and traps gases. This builds immense pressure, leading to highly explosive eruptions and the formation of steep-sided structures like lava domes.
7. What determines the formation of different lava flow textures like Pāhoehoe and ʻAʻā?
Both Pāhoehoe and ʻAʻā are textures typically found in basaltic lava flows and can even originate from the same eruption. The main difference is caused by the lava's viscosity and rate of flow. Pāhoehoe forms when lava is hot and flows slowly, creating a smooth, billowy, or ropy surface. ʻAʻā forms when the lava cools, becomes more viscous, and moves faster, causing the surface to tear into a rough, jagged, and blocky crust.
8. Is it true that some volcanoes produce blue lava? What causes this phenomenon?
The lava itself is not actually blue. The incredible phenomenon of 'blue lava', famously seen at the Kawah Ijen volcano in Indonesia, is not caused by the molten rock but by the combustion of volcanic gases. The volcano emits large quantities of sulphuric gases at very high temperatures. When these gases come into contact with oxygen in the air, they ignite and burn with an electric-blue flame. This burning sulphur can flow down the slopes, creating the illusion of blue lava, especially at night.
