What rock is formed by rapid cooling?

What rock is formed by rapid cooling?

Extrusive igneous rocks
Extrusive igneous rocks cool much more rapidly than intrusive rocks. The rapid cooling time does not allow time for large crystals to form. So igneous extrusive rocks have smaller crystals than igneous intrusive rocks.

Which texture elements are directly related to cooling rates?

Exercise 5: Igneous Rocks

• Texture — the size of the crystals can be crudely related to the rate of cooling.
• Mineralogy — N.L.
• Note that a granite is the coarse grained equivalent of a rhyolite.

Which type of igneous material cools fastest?

Extrusive igneous rocks form after lava cools above the surface. Extrusive igneous rocks cool much more rapidly than intrusive rocks.

What is the texture of a rock with a complex cooling history?

Some igneous rocks undergo a complex cooling history as a result of the movement of magma to a different environment from which the initial cooling began resulting in large crystals (phenocrysts) embedded in a fine grained small crystal matrix (groundmass) resulting in a porphyritic texture.

How do cooling conditions affect texture and composition of igneous rocks?

Extrusive or volcanic rocks crystallize from lava at the earth’s surface. The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals. They cool too quickly to form crystals.

How does cooling rate affects grain size in igneous rocks?

As magma cools, it begins to crystallise and form solid rock. If magma is trapped underground in an igneous intrusion, it cools slowly because it is insulated by the surrounding rock. Crystals have more time to grow to larger size.

What is the fastest cooling igneous rock?

Intrusive rocks form plutons and so are also called plutonic. The fastest cooling of these form obsidian, volcanic glass. The magma turns solid as it cools, and eventually becomes rock. Igneous rocks are formed as magma from below the earths crust cools and hardens.

What does the texture of this rock indicate about its cooling history the magma cooled?

The texture of an igneous rock is determined by the cooling history of the magma from which it formed. Phaneritic texture describes coarse grained rocks. They are characteristic of intrusive (plutonic) rocks, and have crystals that can be seen with the unaided eye. Indicates slow cooling history.

What effect does a fast cooling rate have on grain size in igneous rocks?

The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals.

What happens to crystal growth during rapid cooling?

Slow cooling results in only minor undercooling (Ta ), so that rapid growth and slow nucleation produce fewer coarse-grained crystals. Rapid cooling permits more undercooling (Tb ), so that slower growth and rapid nucleation produce many fine-grained crystals. Very rapid cooling involves little if any nucleation or growth (T c ) producing a glass.

Which is the best description of a texture?

Texture- description of the degree of crystallinity, grain size and shape, and arrangement of the minerals

What kind of texture does a phenocryst have?

•Porphyritic texture: distinct bimodal distribution in grain size, one considerably larger than the other; – i.e., Phenocrysts(large crystals) surrounded by a fine-grained matrixor groundmass Chapter 3: Igneous Textures • Growth rate of a crystal depends upon:

What makes the texture of an igneous rock?

Chapter 3: Igneous Textures The texture of a rock is a result of various processes that controlled the rock’s genesis and, along with mineralogyand chemical composition, provides information that we may use to interpret the rock’s origin and history Table 3.1 at end of Chapter 3 provides a glossary of common igneous rock textures