Table of Contents
- 1 Why is obsidian igneous?
- 2 What is an extrusive igneous rock and how is it formed?
- 3 Why is obsidian amorphous?
- 4 Is obsidian intrusive or extrusive?
- 5 Is Obsidian intrusive or extrusive?
- 6 Is Obsidian extrusive or intrusive?
- 7 What makes Obsidian an extrusive and intrusive rock?
- 8 What does the term massive mean for obsidian?
Why is obsidian igneous?
Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure.
Which is an extrusive igneous rock?
Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff.
What is an extrusive igneous rock and how is it formed?
Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. When lava comes out of a volcano and solidifies into extrusive igneous rock, also called volcanic, the rock cools very quickly.
What igneous texture is obsidian?
glassy texture
Obsidian is the common rock that has a glassy texture, and is essentially volcanic glass. Obsidian is usually black. Now let us briefly consider textures of tephra or pyroclastic rocks. Like lava flow rocks, these are also extrusive igneous rocks.
Why is obsidian amorphous?
Obsidian is hard, brittle, and amorphous; it therefore fractures with sharp edges. In the past, it was used to manufacture cutting and piercing tools, and it has been used experimentally as surgical scalpel blades….
| Obsidian | |
|---|---|
| Fracture | Conchoidal |
| Mohs scale hardness | 5–6 |
| Luster | Vitreous |
| Specific gravity | c. 2.4 |
What causes obsidian to form?
obsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Increased viscosity impedes crystallization, and the lava solidifies as a glass. obsidian boulders. Obsidian boulders formed from lava flow.
Is obsidian intrusive or extrusive?
Obsidian is an “extrusive” rock, which means it is made from magma that erupted out of a volcano. If it was an igneous rock that formed from magma underground and did not erupt, it would have been called an “intrusive” rock.
Why do extrusive rocks have air pockets?
Extrusive rocks have air pockets because in the process of cooling, they can trap air within the magma or lava.
Is Obsidian intrusive or extrusive?
Which is the extrusive igneous structures?
Extrusive Igneous Rocks: These are the rocks that form at erupting volcanoes and oozing fissures. The magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere.
Is Obsidian extrusive or intrusive?
Why some igneous rocks has a glassy texture like the Obsidian?
Very quickly cooled lavas, typically those quenched in water, will have a glassy texture. They cool too quickly to form crystals. Glasses do not have an orderly arrangement of atoms and there are therefore no minerals, in the strict sense, in them. Volcanic glass is called obsidian.
What makes Obsidian an extrusive and intrusive rock?
Obsidian is an “extrusive” rock, which means it is made from magma that erupted out of a volcano. If it was an igneous rock that formed from magma underground and did not erupt, it would have been called an “intrusive” rock. Obsidian: Can we get started already? I don’t have all day! Rondi: Sorry, folks. Obsidian is a bit hot-tempered.
Which is an example of an extrusive igneous rock?
Obsidian is an extrusive igneous rock, not an intrusive igneous rock. Obsidian is a great example of a fine grained extrusive igneous rock. This rock is an example of glassy surface when lava quickly cooled on the earth’s surface. For more information on obsidian visit this article “ All about Obsidian ”.
What does the term massive mean for obsidian?
Obsidian. Obsidian is a massive volcanic glass. The term ‘massive’ has several (although related) meanings in geology but here it means that the rock (obsidian is a rock type, not a mineral) is homogenous. It lacks layering, cleavage, foliation, phenocrysts, etc. It is just a piece of volcanic glass without further conditions.
Why does obsidian have a glassy texture?
The rapid cooling of lava results in a fine-grained texture, or in this case (with obsidian), a glassy texture, where cooling takes place so rapidly that mineral crystals do not have time to form. Rock that is formed from slow cooling magma beneath the surface is intrusive igneous rock, and exhibits visible mineral crystals.